A/C randomly stops working (relay was replaced)

I'm a bit confused as to what might be going on here...

 

A/C blows ice cold.

 

At random times, the compressor will stop engaging at which point I shut the system off, wait a few seconds then power it on again. A/C goes back to blowing ice cold and the circle goes from there.

 

Could be 2 minutes, could be 20 minutes.

 

I replaced the relay with a new OEM and while things seemed to improve, the issue still exists.

 

No indication of a leak and if the system were leaking, there would eventually be no cold at all.

 

I am at the point where I believe the cabin temp sensor on the driver's kick panel might be the point of failure or there's an issue with the electronics in the HVAC controls but I wanted to consult the forum before getting into this any further.

What are the High and Low pressures at idle? 3000rpm? It could be a bad output from the HVAC control, you would have to do some testing when it fails. (Manifold gauges hooked up and a meter or probe to check signal to the compressor (or sensors).

 

Found a diagnostics chart:

 

https://legacygt.com/forums/showthread.php/hvac-test-mode-reseti-fan-seems-slower-than-normal-226170.html

Edited July 24, 2021 by Marvick08GT

Does it still happen if you set the A/C to 68 rather than 65?

Marck - Haven't checked the system pressure but thank you for the link. Wonder if that self diag sheet is from vaca pix...? I'll have to look into that

 

 

Does it still happen if you set the A/C to 68 rather than 65?

 

I would say yes, compressor eventually stops cycling regardless of temperature setting.

 

Although, yesterday while driving in the rain for most of the day it seemed to me the compressor was cycling perfectly fine the entire time as none of the windows were fogging at any point.

 

And today, sunny and 80 and things are as described in the OP.

So I went through my vaca pix and found the entire section of the HVAC system diag. (pg 4095)

 

Being that the LCD did not correctly show system diagnostics enabled, I took a step back and performed the test steps for the display, which also failed. (pgs 4102-4103)

 

Recommendation is to replace the A/C control panel. Do I understand the translation of that to be "find another radio/HVAC assy"?

That sounds like the solution. Shame I tossed mine months ago. I'd have given ya mine for free.

I have a duel climate 05 Hvac/radio. PM if you're interested.

Will an 05 radio/HVAC set up work in a 2008?

 

That sounds like the solution. Shame I tossed mine months ago. I'd have given ya mine for free.

Appreciate the thought.

I presume it will, given I have an 07-08 in my 05.

Edited July 28, 2021 by Mechazilla

I have the 07-08 P-204-uh radio I think if you need one.

I can double check tomorrow if needed.

The 204 is better than the 201 I have.

^^^^

If possible, I would like to stick with the 204. In the event that doesn't work out, I'll be in touch.

Hey Bergs, any chance you were able to access the self diagnosis mode on the A/C? I'm having issues. I press the two buttons and turn the car on and nothing.

There are two levels of self diag, the control and the system.

 

In my case I was unable to enter system diag since the display did not illuminate as described in the manual so I tried the control diag, at which point I recorded failures within the various button presses.

 

To enter control diag, the two buttons are AUTO and MODE

 

To enter system diag, the two buttons are A/C and Front Defrost.

What happens if you try the diagnostics with the replacement head unit?

Do you experience the same errors or something else?

Same symptoms with regards to the described A/C issue.

 

The control diagnostics fails on the replacement head unit, albeit for different inputs and with fewer failures in total as compared to the original head unit.

 

Also unable to access system diag on the replacement unit.