Ok so my 90 legacy LS wagon is having some issues with climate control, the heater wont blow hot air unless I am driving and when I'm idling it will blow cold air and the temperature gauge starts to go up like it's overheating. I have a few suspects either the climate control module because the DEF button does nothing and during the summer the A/C will kick on and off randomly, and/or the ECU as I've had a check engine light on intermittently for a while and did the diagnostic and it blinked as if nothing is wrong and the other reason I guess the ECU bad is cruise control doesn't work but the button does light up any ideas? Thanks in advance!

Uhm... when the needle starts to climb like it's overheating, IT IS overheating!!!

 

I tend to believe your problem is not the climate controls, but an air bubble in the cooling system. The bubble is probably at the heating core (hence blowing cold air), and preventing the coolant from circulating correctly (leading to the engine overheating).

 

Have you checked the coolant level? Have you tried to burp the system recently? The other problems you mention may or may not be related.

Edited January 25, 201214 yr by jarl
Getting used to new keyboard...

I have not, but I will try those and report back. It just seemed strange to me that it only starts to overheat when it is idling and blowing cold air, if it idles and blows hot air then it doesn't over heat and if I don't have the heater on at all it wont over heat.

I did check the coolant level and it was low. I have not tested to see if that solved the issue as it has not been cool enough to test it out yet but I will post my findings as they are made available

Edited January 30, 201214 yr by Goobysoobs

Another possibility could be a partially blocked heater core.

I did check the coolant level and it was low. I'm have not tested to see if that solved the issue as it has not been cool enough to test it out yet but I will post my findings as they are made available

 

I had the same issue, same year and model, the fluid in the radiator was extremely low, filled it up, burped it and haven't had an issue since:headbang:

Yeah that was it. Filled it, burped it and now it's working again. Never had it leak or anything... wonder what happened to the coolant that was in there. I'm addressing all those other issues now as I'm going to be having to do a drive to Raleigh, NC and I'd rather not break down in the midwest.

Edited January 30, 201214 yr by Goobysoobs

I'm having a similar issue, how do you burp the radiator? I had a new one put in a few months ago.