WASHINGTON (Reuters) - U.S. Senator Elizabeth Warren called on Federal Reserve Chair Janet Yellen to remove members of Wells Fargo & Co’s board after revelations the company improperly charged customers for auto insurance. In a letter sent Friday to Yellen, Warren, a Democrat, said the recent revelation of more improper charges at the bank indicates “deep risk management problems,” and called for the removal of all board members who served from 2011 to 2015, when the activity reportedly occurred. The New York Times reported Friday that more than 800,000 Wells Fargo customers were charged for auto insurance they did not request. 