A/C intermittently blows hot air

Football-Ref · Post by **Football-Ref** » 18 Jul 2003, 08:17

My 1996 850 A/C intermittently blows hot air. It's fine in the morning when it's cooler outside, but lately it's been consistently in the 90's in the afternoon and that's when it will occassionally blow hot air. It's returns to cold air in a couple minutes, but usually does it again. Any suggestions?

Post by **matthew1** » 18 Jul 2003, 09:35

Recharge AC. If that doesn't do it, it's likely your evaporator, and that's a big job; most people take it in to have it done.

MarcLuxJD · Post by **MarcLuxJD** » 28 Jul 2003, 18:06

If you lose cool air on loading engine [acceleration or climbing] you might have a vacuum leak like I did. The decreased vacuum is failing to hold open the air duct doors that normally keep air passing over the cooling evaporator. I have been told there are three possibilities:
1. The reverse flow vacuum check valves on the exterior firewall are blocked open, letting vacuum 'escape' when the engine is loaded down. This is a cheap fix.
2. The diaphragm or bellow on the air motors under the dash are leaking so they don't hold a vacuum for long. This might be awkward to get at.
3. Any of the connecting vacuum hoses might be leaking.

A cheap fix found here and elsewhere is to block open the diaphragm by pluging a vacuum hose to keep it open all the time.