A/C Question

[564crewdog]

Hello all, still a ZR1 noobie with a dumb question...

Starting status: I have a 1990 Z with 32K miles. A/C and heat work fine, I get a intermittent error on the HVAC that breaks out to a faulty SUN LOAD SENSOR. I've since replaced the sensor and I still get the error sometimes but it clears relatively quickly.

Question 1: When at a stoplight for more than a minute or so, while the A/C is on, it will start to blow warm and humid. Once I get moving again the A/C gets cold, is this normal?

Question 2: Is this normal operation because of not having a constant fan sucking air through the condenser/radiator?

Question 3: Is this situation related to the SUN LOAD SENSOR issue?

Thank you in advance!

[gbrtng]

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Question 1: When at a stoplight for more than a minute or so, while the A/C is on, it will start to blow warm and humid. Once I get moving again the A/C gets cold, is this normal?

Thank you in advance!
Not normal if both fans are running like they should be. Get out and look. Does the coolant temperature go up too?

[564crewdog]

Yes, the coolant temp goes up while sitting at a red light. The fans do come on when the coolant gets warm, but I have not checked to see if the fans run while the A/C is turned on.

[gbrtng]

Both fans run when the AC is on and the vehicle speed is below 40 MPH. Turn the AC on when stopped and you should hear both fans start immediately. The C4 makes a lot of fan noise ...

[564crewdog]

I just checked it in the garage, it sounds as if the right fan (passenger side) is running but I can't visibly see it and the left side is not running (drivers side)... Looks like my prob. Is the controller or the fan itself the usual suspect?

[gbrtng]

See if the left fan blades spin - if not, there is probably a small stone or something keeping it from running. If it does not spin - remove the restriction and then look for a blown fusible link at the junction terminal behind the battery. If it does spin, the motor isn't getting power, so swap the two fan relays on the left front inner fender panel to see of the problem follows the relay. Both relays get their "on" signal from the ECM (I think) so if one fan runs, the problem is either a relay, the wiring from the relay to the fan motor, or the motor itself.

[564crewdog]

Alright, I have some troubleshooting done and I'm a bit confused...I unplugged the fan switch and both fans turned on. I was incorrect when I said one fan turns on when the A/C is on, they both do not run. I swapped the fan relays on the radiator shroud and still no joy. I know the fans come on when it heats up, can this be an ECM problem?

[gbrtng]

System is low on freon. And that's not a fan switch - it's a safety switch that protects the compressor when the system is low on freon - it just happens to also cause both fans to run.

[WVZR-1]

Sounds like low Freon but if this is a C68 auto AC car you should have maybe a flashing light at the AC control panel and you should also be able to do the diagnostics from the C68 control panel. See the C68 section of your FSM!

[564crewdog]

I ran the diagnostics but I'm not getting (09) low freon...

[564crewdog]

SOLUTION
My problem was solved by replacing the fan pressure switch AC Delco part #15-2351 GM part #14078970 (closest to the fire wall)...found it on eBay for $20. Hope this helps anyone with the same symptoms listed here:)