I changed the evaporator on my wife's old but low miles blazer, got ready to start it up. No blower. Blower worked fine before replacing evaporator. Checked the fuses. Replaced Blown #9 HVAC fuse. Blower and AC worked fine that night. But blower did hum a little. Next day, No Blower, Fuse blown again, replaced, blown. Disconnected Blower, Relay, Resister, Compressor, individually and all at once. Still blows fuse. Fuse only blows when the control is turned from off to Max AC, AC, or one of the heat positions. New compressor is installed. Searched all the wires I can, none are grounded. Blowing fuses is driving me crazy! Any help much appreciated.

 

Here's a diagram of 99 manual ckt. Prob. same as yours
Has nothing to do with a/c per se if fuse doesnt blow in 'off'.
One section of the mode sw conducts power to blower resistor/ high spd relay in all working positions.
Pull relay.
Get test lite. Put probes across blown fuse. If lite is not on, turn mode to any on pos, turn speed sw slow and see if it blinks between positions. If it does, short is toward resistor. Disconnect res assy. still shorted?

 

Thank you for your schematic. I have traced it to the pressure switch on the new compressor. For some reason, the pressure switch is grounded and that is what is blowing the fuse. When I bought the compressor, the guy at the store installed the switch for me since it requires snap ring pliers which I don't have. It is a self contained unit with an oring and an opening in the bottom to sense pressure. It is new but somehow it is grounded. There is two wires that plug into it, one of which is hot when the ignition is on. Any advice on that appreciated also. Thanks again