HVAC Solenoid

[joeuser742]

I can't seem to find the HVAC solenoids. I'm having problems with the A/C not turning on and am looking for the A/C solenoid. I looked behind the glove box and also took apart the dash panels. I already checked the high and low pressure switches (both closed, good PSI), grounds, and continuity on all the wires. Can someone give me some direction and what it looks like and if I can swap the solenoids around?
It's a 98 with climate control.

[BlazerLT]

first, the compressor not turning on is because the refrigerant is too low or the low pressure switch is bad.

Both will stop it from turning on. I would check either situation first before going into the relays.

[joeuser742]

Originally Posted by BlazerLT

first, the compressor not turning on is because the refrigerant is too low or the low pressure switch is bad.

Both will stop it from turning on. I would check either situation first before going into the relays.

I already checked the switches (both are in the shorted/closed state) and the refrigerant (high and low side are at a good psi). Some mornings, the A/C will work, but most of the time it will not come on. I checked fuses, relay, and wiring. The last things that needs to be checked are the HVAC solenoids and the sensors, which is the reason why I was asking where they are.

[joeuser742]

Update, I found the solenoids. They work fine. This morning, the air worked again. Last night I noticed that there was no request (signal) coming from the climate control module, this morning, there was. Maybe there is a cold solder joint or a component going bad inside.

[joeuser742]

Final Update...
Finally, I found a bad outside ambient air temperature sensor, located behind the grill. This was causing the A/C compressor not to come on (it did occasionally work in the mornings). It looked to be an open circuit and without the connection, the request to the A/C could not be made.

[BlazerLT]

Weird.....

How does that sensor stop the AC from not working?

[joeuser742]

I couldn't say for sure, but if I had the schematics for the computer climate control, then I could (I only had the wiring diagrams). My guess is that the sensor completes the circuit for the A/C request. The sensor adjusts it's resistance as the outside temperature changes.

[BlazerLT]

Guess it might not turn on the AC when the outside temp is too cold and damage the compressor.

Makes sense.

[joeuser742]

That sounds about right. I'll have to test that when it gets really cold out, if I still have the truck.