Air Conditioning gremlins!!
 

A month ago my A/C was working fine with absolutely no issues. Then one morning I warm the car up, turn on the A/C and nothing happens, no air, no snowflake, compressor does not engage.

1. checked all fuses and relays - working fine
2. checked A/C blower fan, located under the passenger dash, I tested it and its functioning.
3. checked high and low side pressure - normal, no visible leaks

I was going to check the compressor but didn't know how since the A/C button did nothing. However when I removed the Blower Fan the A/C button functioned normally and the Snowflake popped up and compressor engaged. The compressor engages only when the Blower fan is removed obviously no air can move through the vents.

If I unplug the Blower Fan then as a result the A/C button turns on, and the compressor engages. as soon as I plug it back in the compressor shuts off. :(

Ignition switch is my guess, especially if it randomly starts working again. I bought a 98 back in 2011 that needed some love. One thing PO mentioned was AC blows cold but sometimes doesn't work. It was blowing cold during my test drive and drive home. Next day, no air. FWIW, stereo did the same thing.
$15 later, everything worked great.

Forgot to mention I bought a new ignition switch at AutoZone installed it, no change. Bought a the Duralast LS901.


The fan doesn't function at all, as the fan sits plugged in, it doesn't spin on any setting. When I press the A/C button, the snowflake doesn't show on the LCD and the Compressor fails to engage. BUT if I unplug the A/C Blower and press the A/C the snowflake appears, Compressor Clutch engages, and whats weird is I have to remove the fan in order for the A/C to turn on and work.

I installed a brand new ignition switch yesterday, and it changed nothing.

Ok. Run 12 Vdc directly to the blower assembly and see if it works. Given the fact that everything else goes away with the blower installed, it may be creating a load that makes the rest of the system inoperable.

If the blower works with 12 volts applied directly, I have no idea what you'd do next but given what you've found so far, you need to determine if your blower is good or bad.

I have removed the fan hooked it up to a 9V battery source and the fan started working flawlessly.

Maybe someone has a climate control unit you can swap out to see if that's you issue. Sorry but no other ideas off the top of my head.

in that case, it might be the fan resistor.
this is the red cube attached to the AC box, and controls the fan speed.

Ok heres an update on my troubleshooting. I checked high and low side pressure again today and the low side is normal 30psi average and the high side shows no pressure. this is with the car running and A/C on and compressor engaging. any idea why high side pressure is at 0 psi ??

Hi David.
I sent you a PM.

It sounds like your compressor may be done. No hi side pressure, with the clutch engaged, is bad. Is it making a lot of noise? If you have 30 on the low side, you should also see 30 on the hi side. It is a closed loop.

Ok that 0 psi reading was a fluke. apparently something was obstructing the gauge from properly reading the pressure. sure enough I removed everything reinstalled it and the pressure gauge showed a value of 25-35 psi for the low side & 200 psi on the high side.

Im suspecting the Blower Motor resistor, but wouldn't a bad resistor just allow the fan to blow high on every setting?? How do I test it?

no abnormal noise that I can hear. if the blower fan is plugged in the A/c won't turn on but if I unplugged the blower fan and turn the A/c on, snowflake shows on the LCD screen and the compressor engages. I tested the high and low ports and the PSI values are normal.

Tomorrow I will remove the blower resistor and see what I can find.

It sounds like your compressor is okay and that is very good news.

I have zero experience with the blower motor circuit on this car. If you can isolate the blower motor, try to run it with 12 volts directly. Proceed with caution. I understand access to the HVAC system is tight and involved.

I wonder if the dash control unit is acting up. Check with Woody (itsnotanova) for possible used parts.

Hi David.
Did you manage to sort it out?