body and is separated from spring 148 by a predetermined distance this distance will vary but is usually about one fourth of the depth of groove 112 and prevents destruction of the plastic body 130 if the resilient lever 126 pushes the plunger 142 down against the contact too far due to improper attachment of the body 130 to the housing 14 the contact 150 is connected by lead 152 to indicator light 154 in the vehicle a flow control or proportioning means 28 located in the second chamber 34 has a proportioning piston 156 with a large diameter 158 and a small diameter 160 the large diameter 158 of piston 156 is located in a corresponding large diameter 162 of a bore 166 and the small diameter 160 of piston 156 is located in a small diameter 164 of the bore 166 a passage 168 extends through the third piston 156 and communicates the second chamber 34 with a distribution chamber 170 the distribution chamber 170 is connected to the outlet port 172 which is communicated to the rear wheel brakes 26 through passage 174 and groove 176 the small diameter section 160 of the piston 156 has a shoulder 178 on the end thereof for retention of a washer means 180 the washer means 180 has a disc 182 which fits on the shoulder 178 and extends into a guide surface 184 on the plug means 52 a spring 186 is caged between the disc 182 and a retainer 190 the retainer 190 is attached to the end of the plug means 52 the spring 186 urges.