text: as shown in fig1 a domestic dishwasher 50 includes conventional upper and lower racks 51 and 52 for supporting food ware , such as cups , saucers , plates and silverware , within a tank 54 . tank 54 forms the rear , bottom , sides and top of a wash chamber 55 , with the front of chamber 55 defined by a door ( not shown ) which closes tank 54 during washing and rinsing of the food ware . a sump 56 in the bottom of tank 54 comprises part of wash chamber 55 , and a pump housing 58 is positioned within an opening formed in sump 56 . a fluid seal is formed between sump 56 and housing 58 by an annular gasket 59 , fitted about housing 58 . primary reaction spray arms 60 having a plurality of spray orifices ( not shown ) defined therein are supported on a fixed shaft 62 at the top of housing 58 . as shown in fig1 and 2 , the pump housing 58 encloses both a recirculating pump impeller 65 and a drain pump inpeller 66 . recirculating pump 65 and drain pump 66 are fixed to a drive shaft 67 , driven by a reversible motor 68 mounted beneath sump 56 . drain pump 66 is part of a drain system which has an inlet opening 70 in the bottom of sump 56 for pumping fluid from the dishwasher 50 , through a drain line 71 , and into a suitable conventional drain ( not shown ). in the embodiment shown in fig1 and 2 , a primary spraying system includes recirculating pump inlet 72 , located in sump 56 . inlet 72 is protected by a main filter screen 74 supported by the outer edge of a circular plate 76 forming a part of pump housing 58 to prevent large food soil particles from entering the recirculating pump 65 and blocking or clogging the spray orifices in arms 60 . a means for collecting soil particles , independent of the primary spraying system , consists in part of a collection inlet 80 , which is common with drain pump inlet 70 , a soil collector body 82 integral with pump housing 58 , and a fluid inlet conduit 84 extending from the inlet 80 through the collector body 82 . collection inlet 80 is located substantially at the bottom of sump 56 to expedite removal of food soil since it tends to precipitate out of the circulating fluid toward the sump at the bottom of the wash chamber 55 . the fluid inlet conduit 84 is contained within the pump housing 58 . pump housing 58 includes a lower housing base plate 90 and an upper section 92 . base plate 90 defines a passageway 94 which comprises a continuation of the sump 56 beneath the upper section 92 to the circuit inlet 80 . the drain pump 66 , which is contained within the base plate 90 , includes a circular pump recess 96 defined by wall 98 , a drain channel 100 , and a soil collector channel 102 . the drain channel 100 forms a part of the drain line 71 and the collector channel 102 forms a part of the fluid inlet conduit 84 . drain impeller 66 is mounted within recess 96 , and is covered by a cover plate 104 having an opening 106 concentric with the impeller 66 which comprises the soil collecting inlet 80 and drain system inlet 70 . cover plate 104 further defines a circular cut - out 110 above collector channel 102 which forms a nozzle 112 with the curved wall 114 of the base plate 90 . nozzle 112 is partially shielded from fluid flowing along the passageway 94 by a shield 113 and base plate 90 . a fluid channel 117 , defined in upper section 92 of housing 58 , extends downwardly from the collector body 82 to an opening 118 in plate 76 at a point slightly above the nozzle 112 . a gap in the fluid inlet conduit 84 is thereby formed above the nozzle 112 , placing conduit 84 in fluid communication with passageway 94 at that point . the collector body 82 includes an annular collection chamber 120 defined within the upper section 92 of housing 58 . collection chamber 120 includes a floor 122 which slopes toward a fluid inlet opening 124 to facilitate draining the chamber 120 . opening 124 communicates with the upper end of fluid channel 117 . the collector body 82 also includes a fine filter screen 126 which covers a fluid outlet 128 that is generally annular in shape and concentric with the pump housing 58 . screen 126 preferably includes a nylon mesh 130 extending between and molded into a frame 132 having support spokes 133 . mesh 130 preferably comprises substantially square openings 0 . 0106 inches ( 0 . 0289 cm ) on a side and is 44 % open . screen 126 is retained by screws 134 to the top of the pump housing 58 . a deflector plate 136 is also molded into the screen 126 and is positioned above the fluid inlet opening 124 in order to deflect fluid entering the collector body from the fluid channel 117 . plate 136 is inclined relative to the screen 126 so that fluid impinging upon its underside is deflected about the soil collection chamber 120 . as shown in fig2 the fluid outlet 128 is enclosed by a shroud 142 which has a rotatable portion attached to spray arms 60 and a fixed portion attached to the main screen 74 . shroud 142 comprises a disc - shaped inner member 144 and an annular outer member 146 . outer member 146 is arcuate in section and includes a lower lip 148 which engages the main screen 74 , and prongs 150 depending downwardly to engage the periphery of the frame 132 . the inner member 144 is integral with the spray arms 60 and its outer periphery defines an inverted , u - shaped channel 152 which engages an upper rim 154 of the outer member 146 to form a labyrinth seal . the labyrinth seal permits rotation of the inner member 144 with respect to the outer member 146 during operation of the primary spray means . inner member 144 also includes conduits 156 having downward opening orifices 158 located above filter screen 126 , and in fluid communication with the spray arms 60 and hence recirculating pump 65 . orifices 158 form spray jets to clean the filter screen 126 and promote flushing of the soil collection chamber 120 . the operation of the dishwasher is described below . when the dishwasher 50 is operated in a washing or rinsing cycle , the primary spray means operates in a fluid recirculating mode in which it recirculates and sprays fluid from the sump 56 onto the food ware . the recirculating pump impeller 65 is activated by the drive motor 68 so that the recirculating pump 65 draws fluid through the recirculating pump inlet 72 and pumps it up through the pump housing 58 to the spray arms 60 . fluid entering the spray arms 60 exits holes formed in the arms ( not shown ) and is sprayed upon the food ware in a manner well - known in the art . the fluid entering the recirculating pump inlet 72 from the sump 56 is strained through the main filter screen 74 so that the larger food soil remains within the sump and only filtered fluid is pumped by the impeller 65 to the spray arms 60 . at the same time the recirculating pump 65 is operating in the recirculating mode , the drain pump impeller 66 is operating in a soil collecting mode . the drain pump impeller 66 rotates in a forward mode on the drive shaft 67 with the recirculating pump impeller 65 , thereby pumping fluid flowing from sump 56 through soil collecting circuit inlet 80 along the soil collecting channel 102 of the fluid inlet conduit 84 . the fluid path is shown by arrows 160 in fig2 . fluid pumped along the fluid inlet conduit 84 is accelerated as it passes through nozzle 112 and is directed upwardly along the fluid channel 117 , through the fluid inlet opening 124 , and into the soil collection chamber 120 of the soil collector body 82 . as the fluid is pumped along fluid inlet conduit 84 , the swirling action of the fluid between the outer periphery of the drain impeller 66 and the wall 98 of the pump recess 96 creates a slight negative or zero pressure in the drain channel 100 which prevents fluid from flowing into the channel 100 during the soil collecting mode . thus , the geometry of the drain pump impeller 66 and the pump recess 96 act to form a valve which prevents flow of fluid through the drain line 71 during the soil collecting mode . of course , it will be recognized that in the alternative drain line 71 may include a controllable valve suitable for preventing flow through drain line 71 when the dishwasher 50 is operated in the recirculating mode . the relatively high pressure and high velocity fluid stream exiting from the nozzle 112 and traveling upwardly along the common fluid channel 117 tends to draw along with it fluid and suspended food soil present in the passageway 94 in the immediate region surrounding the shield 113 which partially encloses the gap . the nozzle 112 thus acts as an injection pump by entraining fluid and food soil from the sump 56 within a stream of fluid entering the soil collector body 82 . once the fluid and suspended food soil enters the soil collector body 82 , it impinges upon the deflector plate 136 and is diverted from its substantially vertical path to a substantially horizontal path around the circular soil collection chamber 120 . as the collection chamber 120 fills with fluid and food soil , the fluid exits up through the fluid outlet 128 of the soil collector 82 and is strained through the screen 126 , thereby leaving the food soil within the collection chamber . the strained fluid , now substantially free of soil particles , travels over the top of the screen 126 and downwardly beneath the shroud 142 . the fluid is deposited in the recievulating pump inlet 72 between the upper section 92 of the pump housing 58 and the main filter screen 74 . food soil is retained within the chamber 120 since the relatively high velocity stream of fluid entering the inlet 124 prevents reverse flow of soil through the inlet . during the soil collecting mode , a portion of the fluid pumped through the recirculating pump 65 enters the conduits 156 formed in the inner member 144 , and communicating with the primary spray arms 60 , where it passes through the orifices 158 and is directed upon the upper surface of the screen 126 . as the primary spray arms 60 rotate during the recirculating mode , the spray jets from the orifices 158 traverse the nylon mesh 130 of the screen 126 to backflush the mesh 130 . this spray , along with the swirling action caused by deflection plate 136 , tends to prevent clogging of the mesh 130 by food soil retained within the soil collection chamber 120 , so long as the amount of soil therein stays essentially below a predetermined concentration as will be discussed below . in addition , the inner member 144 and shroud 142 prevent large food soil particles from getting onto the screen 130 during the recirculating mode . when the dishwasher 50 is operated in a drain cycle , recirculating pump 65 operates in a fluid draining mode . in this mode , the pump motor 68 reverses the direction of its rotation of the drive shaft 67 , thereby causing the circulating pump impeller 65 and drain pump impeller 66 to reverse rotation . with regard to the recirculating pump impeller 65 , reverse rotation causes some fluid to be pumped from the pump inlet 72 toward the primary spray arms 60 and conduits 156 within the inner member 144 of the shroud 142 . this fluid passes through orifices 158 , through the nylon mesh 130 , and into collection chamber 120 . due to the geometry of the drain pump recess 96 and drain pump impeller 66 , however , reverse rotation of the drain impeller 66 causes the fluid entering the drain pump inlet 70 to be swirled in an opposite direction and pumped along the drain channel 100 to the drain line 71 and ultimately to a drain . since there no longer is a relatively high - velocity , high pressure stream of fluid flowing upwardly along the fluid channel 117 , there no longer is a high pressure stream of fluid entering the collection chamber 120 to prevent fluid flow downwardly through the fluid inlet opening 124 . accordingly , the soil collecting circuit operates in a soil discharging mode as the fluid from orifices 158 and the retained food soil within chamber 120 flow across the downwardly sloping floor 122 and into the fluid inlet opening 124 . fluid and food soil continue to flow downwardly along the fluid channel 117 and enter the gap between the fluid channel and the nozzle 112 . at this point , the fluid and food soil either continue to flow downwardly through the nozzle 112 and along the soil collecting channel 102 to the drain channel 100 , or the fluid and food soil flow along the plate 104 and re - enter the drain pump 66 through the drain pump inlet 70 , passing through to the drain channel 100 . it will be recognized that as the dishwasher 50 is operated in a soil collecting mode , the collection of food soil within collection chamber 120 and the passage of fluid through the mesh 130 causes the mesh to become partially clogged by soil particles despite the backflushing of mesh 130 provided by orifices 158 . since the fluid flow into chamber 120 is substantially constant during this mode , however , the reduction in available area along mesh 130 for fluid flow out of chamber 120 will impede the flow therethrough , causing fluid back pressure therein to increase . as shown in fig2 and 3 , the improvement of the present invention includes a sensor means comprising a single - pole , double - throw pressure switch 165 mounted outside of wash chamber 55 . a pressure chamber 166 is mounted within collection chamber 120 adjacent deflector plate 136 , partially formed by an inner side wall and two end walls . an outer side wall is formed by upper section 92 of housing 58 , and a top cover 167 adjacent mesh 130 encloses the top of chamber 166 . the bottom of chamber 166 is open and in free fluid communication with soil collection chamber 120 . a length of flexible tubing 168 has an upper end 169 thereof disposed within chamber 166 substantially near the top cover 167 . tubing 168 extends downwardly from chamber 166 , passing through chamber 120 , floor 122 , plate 76 , and base plate 90 , and communicates at a lower end thereof outside wash chamber 55 with pressure switch 165 . as soil particles are collected within collection chamber 120 and fluid pressure therein increases , the fluid level in the lower portion of pressure chamber 166 rises , compressing the air contained within the upper portion of chamber 166 . air pressure within chamber 166 and tube 168 are thus increased , activating pressure switch 165 . similarly , as fluid pressure within collection chamber 120 is decreased , fluid level within pressure chamber 166 drops . air pressure within chamber 166 and tube 168 is lowered , deactivating switch 165 . consequently , switch 165 is effectively responsive to the degree of fluid flow impedence through filter mesh 130 . it will be recognized that upper end 169 of tube 168 must be located sufficiently close to top cover 167 of chamber 166 so that the fluid level therein will not rise above upper end 169 when fluid pressure within collection chamber 120 is high . suitable wiring is provided ( not shown ) to connect switch 165 to a dishwasher control means , shown schematically in fig4 . the control means is energized from a suitable 60 - cycle power source connected with terminals l1 and l2 . a 141 / 2 cam , 72 - increment timer includes a timer motor 170 for driving the timer at a rate of 75 seconds per increment , and a rapid advance motor 172 for driving the timer at a rate of one second per increment . cam switches c0t - c14t and c1b - c14b of the timer control the various components of the dishwasher 50 in their proper sequence , as illustrated in fig6 . the timer further includes a pair of sub - increment switches 174 and 176 , connected in series with cam switches c13t and c14b , respectively , and operative as indicated in fig7 . an operator - actuated switch means ( not shown ) is mounted to the exterior of the dishwasher 50 so as to enable the operator to select one of three dishwasher cycles , &# 34 ; wash &# 34 ;, &# 34 ; sani cycle &# 34 ;, and &# 34 ; rinse & amp ; hold &# 34 ;, as well as to cancel an already selected and partially performed cycle or to select the use of unheated rather than heated air in the drying process . the switch means is constructed so as to control line switches 180 , 182 , 184 , 186 , 188 , 190 , and 194 in the manner indicated by the table in fig5 according to the cycle selected by the dishwasher operator . upon the opening of a latch ( not shown ) disposed on the door of dishwasher 50 so as to permit opening of the door , an actuator connected to the latch operates the switch means so as to control the line switches as shown in the &# 34 ; reset &# 34 ; column of fig5 . switch 190 is closed , thereby allowing rapid advance motor 172 to be energized through cam switch c1t so as to move the timer through the last several timer increments , shown in fig6 in preparation for the start of a new cycle . an interlock switch 196 is connected between terminal l1 and switch 180 , also associated with the door latch of dishwasher 50 , breaking the power circuit when the door is opened . lead 197 is the primary power lead connected to motor 68 for energizing motor 68 so as to drive pumps 65 and 66 for either washing of the ware or draining of sump 56 . the coil of a starting relay 198 is connected to lead 197 . upon energization of motor 68 , as a result of lock rotor ( rotor speed ), a high current is produced in the coil of relay 198 , thereby closing its contact 199 . depending upon the increment position of the timer , either cam switch c11t or c11b will be closed . if cam switch c11t is closed , closing of contact 199 will cause starting coil 200 of motor 68 to be energized through lead 201 , thereby starting motor 68 in a direction so as to drive pumps 65 and 66 such that pump 66 forces fluid into drain channel 100 . if cam switch c11b is closed , closing of contact 199 will cause starting coil 202 of motor 68 to be energized through lead 203 . motor 68 will then be started in an opposite direction so as to drive pump 65 for circulation of fluid through spray arms 60 and to drive pump 66 for circulation of fluid into fluid inlet conduit 84 . upon starting of motor 68 , the current in lead 197 will drop , allowing contact 199 of relay 198 to open , de - energizing starting coil 200 or 202 . motor 68 may be energized through either cam switch c12b , or cam switch c14b and sub - interval switch 176 . as indicated in fig7 sub - interval switch 176 is normally closed , but opens to provide a ten - second de - energized period near the beginning of a timer increment . switch 176 and cam switch c14b are used whenever the direction of motor 68 is reversed , to permit the motor 68 to coast to a stop before changing direction . pressure switch 165 ( shown in a neutral position for clarity ) is normally disposed with contact member 204 in contact with terminal 206 . at a predetermined pressure within collection chamber 120 , switch 165 is activated and member 204 contacts terminal 208 . member 204 returns to its normal position when collection chamber pressure is reduced below the predetermined level . a thermal relay switch 210 having a heater 212 and a normally open bi - metal switch 214 is provided wherein energization of heater 212 for approximately 75 seconds will warp switch 214 to a closed position . upon deenergization of heater 22 , the switch 214 , due to its thermal inertia , will remain closed for at least 15 seconds . water heater 216 and water heater 218 are connected in parallel by leads 220 and 222 , respectively , so that by selecting a single heater or a combination of heaters 216 and 218 , different heating levels may be obtained . a normally - closed thermostatic switch 224 is connected to heaters 216 and 218 to protect the heaters against possible overheating . a normally - open thermostatic switch 226 is connected by lead 228 to timer motor 170 so that by opening cam switch c4t and closing cam switch c1b , advance of the dishwasher cycle may be made dependent upon temperature within wash chamber 55 , rather than time , for some portion of the cycle . control means for a fill valve 230 is provided for controlling the inlet of water into the wash chamber 55 . a float switch is connected to control fill valve means 230 to prevent overfilling of chamber 55 . fill valve 230 is energized through either cam switch c10t or cam switch c13t and sub - increment switch 174 . as shown in fig7 switch 174 permits fill valve 230 to open for a 15 - second period rather than the full 75 - second increment . thus , by following a 75 - second energization of valve 230 by a 15 - second energization , a 90 - second period may be obtained . an air blower 234 is included to facilitate the drying of ware within chamber 55 , and an air heater 236 is provided for heating the air to be circulated by blower 234 , further facilitating drying of the ware . a normally - closed thermostatic switch 238 is connected to heater 236 to protect against overheating . further , line switch 194 is connected to heater 236 to permit the operator to select unheated air for drying of the ware . a pair of detergent dispensing cups ( not shown ) are mounted to the inner surface of the door of dishwasher 50 . each cup has a lid latchable in a closed position with spring opening means for opening the lids when latches 240 and 242 are released . each latch 240 and 242 comprises a bi - metal strip engageable with a lid . as shown in fig3 latch 240 may be energized through cam switch c0t , while latch 242 may be energized through cam switch c9t . upon energization , the bi - metal latch 240 or 242 is warped away from its engaged lid , thereby releasing the lid and allowing it to open . detergent contained within the cup is thus introduced into wash chamber 55 . a dispenser for addition of a rinse agent to wash chamber 55 is also provided , and is activated by a bi - metal actuator 244 , energized through cam switch c14t . the three selectable dishwasher cycles , &# 34 ; wash &# 34 ;, &# 34 ; sani cycle &# 34 ;, and &# 34 ; rinse & amp ; hold &# 34 ;, generally consist of various combinatios of several operations . sump 56 may be filled or drained . a wash operation includes the circulation of water with detergent in wash chamber 55 . the circulation of water without detergent may be either a prewash or a rinse , and the dry operation includes the circulation of either heated or unheated air . additionally , the &# 34 ; cancel cycle &# 34 ; operation terminates upon selection thereof whichever cycle the dishwasher 50 may be performing , and resets the dishwasher 50 for starting of another cycle . two primary cam switches , c5 and c7 , are used to control the four cycles . &# 34 ; sani cycle &# 34 ; is the lengthiest in time , including one to three prewashes , two washes , a rinse , and a dry , with the necessary associated fills and drains between each operation . the rinse includes a heating period for the rinse water , with period length determined by thermostat 226 . &# 34 ; wash &# 34 ; is identical to &# 34 ; sani cycle &# 34 ; except that the heating period for the rinse water is eliminated by energizing rapid advance motor 172 by cam switch c8t and line switch 186 , shown at timer increment t39 in fig6 . &# 34 ; rinse & amp ; hold &# 34 ; includes only one or two prewashes , with the remaining operations bypassed by energizing rapid advance motor 172 at increment t14 by cam switch c7t and line switch 184 . &# 34 ; cancel cycle &# 34 ; will cause all operations to be bypassed , and is effected by energizing rapid advance motor 172 first at increment t1 by cam switch c8b and line switch 188 , and then at increment t14 by cam switch c7t and line switch 184 . the exact number of prewashes in each cycle is controlled by pressure switch 165 and is dependent upon the soil concentration level within soil collection chamber 120 . &# 34 ; wash &# 34 ;, &# 34 ; sani - cycle &# 34 ; and &# 34 ; rinse & amp ; hold &# 34 ; all provide for at least one prewash per cycle , with a maximum of three for &# 34 ; wash &# 34 ; and &# 34 ; sani cycle &# 34 ;, and two for &# 34 ; rinse & amp ; hold &# 34 ;. the operation of the improvement of the present invention is shown diagrammatically in fig8 which illustrates , in flow - chart fashion , the operation of the &# 34 ; wash &# 34 ; cycle . it will be understood that the operation of pressure switch 165 and the resulting selection of the proper number of prewashes is substantially similar for either the &# 34 ; sani cycle &# 34 ; or &# 34 ; rinse & amp ; hold &# 34 ; cycles . upon starting the cycle , as shown at block 250 in fig8 a 75 - second drain is performed by energizing motor 68 through cam switches c12b and c11t to remove any fluid that may be present within the sump 56 . a 90 - second fill of sump 56 is then performed by activating fill valve 230 at increments t2 and t3 through cam switches c10t and c13t . after filling , water in sump 56 is heated by water heaters 216 and 218 . during heating , at increment t4 , cam switch c4t is opened , deenergizing timer motor 170 . cam switch c1b is closed , so that when water temperature reaches 140 ° f . ( 60 ° c . ), thermostat 226 will close , reenergizing timer motor 170 , thereby ascertaining that water temperature is at least 140 ° ( 60 ° c ). cam switches c12b and c11b are closed at increment t5 , and motor 68 begins circulating water onto the ware by driving pump 65 , seen as a prewash in block 252 . simultaneously , pump 66 , also driven by motor 68 , begins circulating water and accumulated soil through the soil collecting chamber 120 . as soil is collected within collection chamber 120 , pressure within chamber 120 increases . if , however , as shown at block 254 , the pressure does not rise to a level sufficient to activate pressure switch 165 , contact member 204 remains in contact with terminal 206 . the circulation of water by pump 65 continues for a period of 61 / 4 minutes , block 256 , with cam switch c2t being closed for the final 75 seconds of this period , shown at increment t9 in fig6 . heater 212 of thermal relay switch 210 is thus energized , closing bi - metal switch 214 . cam switch c3t closes in the following increment , thereby energizing rapid advance motor 172 to advance the timer past two extra prewashes to increment t18 , wherein the sump 56 is drained by pump 66 , driven by motor 68 which is energized by cam switches c14b and c11t . the remainder of the cycle then follows as shown in block 258 in fig8 . if at any time during the 61 / 4 minute prewash the pressure within collection chamber 120 rises to a level sufficient to activate pressure switch 165 , seen at block 254 , contact member 204 will be moved into contact with terminal 208 . since cam switch c6t is closed during the entire prewash , rapid advance motor 172 is energized to move the timer ahead to increment t10 . motor 68 is then energized by cam switches c14b and c11t , driving pumps 65 and 66 , thereby flushing soil from collection chamber 120 and draining soil and water from sump 56 , shown at block 260 in fig8 . upon completion of the drain , sump 56 is refilled by fill valve 230 and a second , 21 / 2 minute prewash begins , indicated at block 262 . if , as shown at block 264 , the soil collected in chamber 120 is insufficient to cause the pressure therein to activate pressure switch 165 , then , as with the first prewash , cam switch c2t closes for the final 75 seconds of the prewash , shown at increment t13 in fig4 . heater 212 of thermal relay switch 210 is energized , closing bi - metal switch 214 . cam switch c3t closes in the following increment , energizing rapid advance motor 172 to advance the timer to increment t18 . sump 56 is drained , and the remainder of the cycle follows as shown in block 258 in fig8 . if , however , at any time during the second prewash the pressure in collection chamber 120 becomes sufficient to activate pressure switch 165 , seen at block 164 , contact member 204 will again be moved into contact with terminal 208 . since cam switch c6t is closed during the entire second prewash , the rapid advance motor 172 is immediately energized to move the timer ahead to increment t14 . motor 68 is then energized by cam switches c14b and c11t , driving pumps 65 and 66 , thereby flushing soil from collectoin chamber 120 and draining soil and water from sump 56 , shown at block 266 in fig8 . upon completion of the drain , sump 56 is refilled by fill valve 230 , and a third , 21 / 2 - minute prewash begins , indicated at block 268 . if , as shown in block 270 , the pressure within chamber 120 is insufficient to activate pressure switch 165 , the entire prewash is carried out , block 256 , bringing the timer to increment t18 . the sump 56 is drained , and the remainder of the cycle follows as shown in block 254 in fig8 . if at anytime during the third prewash the pressure in collection chamber 120 becomes sufficient to activate pressure switch 165 , contact member 204 will be moved into contact with terminal 208 . cam switch c6t is closed during the entire third prewash , so rapid advance motor 172 is energized to move the timer ahead to increment t18 . motor 68 is energized by cam switches c14b and c11t , driving pumps 65 and 66 , thereby flushing soil from collection chamber 120 and draining soil and water from sump 56 . normally , three prewashes should be more than sufficient to remove even an abnormally high quantity of soil from the food ware within the wash chamber 55 . accordingly , in the event pressure switch 165 is activated during the third prewash , it is far more likely to be due to a malfunction in the soil collection circuit , such as for instance complete blockage of the filter mesh 130 , than due to a general high soil level within wash chamber 55 . thus , during the third prewash , as seen in fig6 can switch c2b is closed . if at any time during the prewash pressure switch 165 is activated , seen at block 270 , closure of contact member 204 and terminal 208 will in addition energize through cam switch c2b coil 272 of relay 274 . as shown in fig4 relay 274 is a double - pole , single - throw normally open relay having a pair of contacts 276 and 278 . energization of coil 272 closes contacts 276 and 278 , with contact 276 connected in series with coil 272 so that once energized , coil 272 will remain so until deenergized by opening of the door of the dishwasher 50 , opening switch 196 . after draining of sump 56 , at increment t18 and as shown at block 280 of fig8 cam switch c6b is closed at increment t19 . rapid advance motor 172 is energized through contact 278 of relay 274 and cam switch c6b , and advances the timer past the remainder of the dishwasher cycle , bypassing all subsequent operations and thereby aborting the cycle . simultaneously with energization of relay coil 272 , an indicator light 282 or other appropriate display device is activated , remaining so until the door of the dishwasher 50 is opened , to alert the operator of the dishwasher 50 that the cycle has been aborted . while the form of apparatus herein described constitutes a preferred embodiment of the invention , it is to be understood that the invention is not limited to this precise form of apparatus , and that changes may be made therein without departing from the scope of the invention , which is defined in the appended claims .