Have a 92 S10 Blazer and the a/c speed control beign acting up lately. Sometimes it stayed in the low speed but after moving the a/c heater control switch around it engaged in the actual speed on the speed control until today. after moving it around only stays in the low speed. Bottom line only works in low speed now. Any suggestions. Thanks

 

Relay or resistor is where I would start. Probably resistor first. But when they burn the coils they usually don't work at all on the speed that the coil's burnt out on.

 

HIGH speed is driven through the blower motor relay which should be located on the firewall between the blower motor & the a/c accumulator. The resistor controls LOW & MEDIUM speeds. If your fan only works on LO speed, I would suspect a problem with the switch itself.