I had the problem of my blower switching from regular to low speed no matter what I have the switch set at. Cold A/C, just no high fan. The Chrysler dealer had hard time figuring out what the problem was. replaced the control head, did nothing, replaced the entire blower, nothing. They finally replaced the fan blower resister which has a ceramic housing and they found cracked. That fixed it. Dont know, maybe thats your delima. Good luck!