2008 S80 - No A/C when Idling

AU-S40 · Post by **AU-S40** » 09 Jun 2013, 22:28

My mom's 2008 S80 has started blowing out hot air when idling. The A/C works perfectly as long as we are moving, and is as cold as it has ever been. It is only when we are stopped for a minute that it begins to get hot. I have VIDA and a DiCE tool, but do not know much about it. I graphed the ECM-A/C pressure over a test drive and noticed that when idling the pressure would reach ~2,800 kPA and that it was at this point when the air was hot. As we moved again, it dropped and the air went back to normal. The next time we stopped for a minute, I activated the engine cooling fan and that brought the pressure back down and the air was once again cool. There were no relevant error codes. Does anybody have any idea what it may be? II have zero experience with A/C systems.

Post by **jimmy57** » 10 Jun 2013, 06:10

When idling is the ECM not starting the cooling fan at a low speed and then ramping up fan speed as high side pressure rises?
Which fan speed level activation are you using to get high side pressure down?

If the ECM is running fan when the pressure is high and you have to go to full fan to get it to come down then cleaning the condenser of bugs and other air blocking debris may be all that is wrong.
The high side pressure is going over 400 psi when it should be held at 300 or less by cooling fan control.

AU-S40 · Post by **AU-S40** » 10 Jun 2013, 10:03

Alright, I just hooked it up and took a quick trip. It looks like the fan did kick on, but just as a quick spurt. I am attaching the graph from when it was idling. When I activated it earlier, I was using the 66% activation.

: Here is the graph; Vida Readout.PNG (84.07 KiB) Viewed 463 times

AU-S40 · Post by **AU-S40** » 11 Jun 2013, 16:21

We took it to the shop and they think it might be the fan control module? Does that sound about right?

Post by **jimmy57** » 11 Jun 2013, 17:21

Yes, from the lack of pressure dropping until the fan signal gets high it would seem the fan is dragging and not achieving speed until the signal gets high. Still could be blockage of condenser airflow path.