AC & heater controls

[gary mcadams]

AC compressor clutch was intermittant. Sometimes on, sometimes off. Found the plug to the high pressure switch loose, you could wiggle it & the clutch would kickin. Got this tightened up and out of nowhere the heater/ac fan quit working. I'm not sure if it's a switch or a fuse problem. I believe that if the main selection switch, heater/vent or ac malfunctions or defaults to off then the fan selection is nulled. Not much on electronics, anyone have any ideas? Going through the OM I couldn't find a fuse for the fan.
Thanks
my bad----02 F350 7.3psd

[gbear]

According to a diagram I have there is a 40 amp fuse feeding power to the contacts on a blower relay located in the central junction box. the relay feed the power to the blower motor. Off the other side of the blower motor goes thru the speed control resistor bank located on the air plentum near the blower motor. It also looks like a internal fuse is on the resistor bank. I hope this is helpful.

[mschn99]

this is actually a relatively simple thing to check. First mesaure to see if there is power on the orange wire at the blower motor. If there is, the fuses are good. Then measure the resistance between the black wire and ground with the key on and blower motor speed to high....it should be under 5 ohms......if you have power and ground its the blower motor itself. If not, we will need to test further....

[gary mcadams]

guys,
thanks for the replies. after looking further into the fuse thing, i found the 10 amp fuse to the blower relay, fuse #28, blown. evidently the high pressure switch was causing a higher amperage pull than the system would tolerate and blowing this fuse. without this fuse, the blower nor the compressor clutch would operate. took the high pressure switch plug apart, wire end, tightened up the female end of the plug put it all back together and all is fine. trying to locate the plug replacement now so it doesn't happen again.
thanks for the input.
gary