E34 cold centre vent, hot side vents?

[kiwi328i 118]

Hi,

My 530i 1993, cools well, actually its hopeless compared to Mum's 15 year old primera that will freeze you to the bone in 5 minutes, but it can actually cool you. I had the AC gassed up last year. I cant remember any hot air coming out of the side vents that come up by the dash speakers, it's actually quite hot. Nothing at all on the feet.

I am guessing something is unplugged or the fascia is not working properly, or the lever is not connected properly, or something to do with the heater control valve.

I have googled this and I am more confused now than before.

I cant see why if I want cold I cant get it coming out wherever I want it to?

Please help, or if you suggest I go somewhere to get it fixed.

Cheers

[kiwi535 538]

probably the heater control valve(s).If its hot when you dont want hot almost certain

[richard.pykett 36]

Hi

For my sins I have a 2005 Audi A6 Wagon, bought at 4ks as an ex demo. Should have gone with the 530, but thought we were going to relocate to Queenstown, so the 4wd was attractive. The front shocks failed a WOF at 60kms and both Contis and EMD said get stuffed. I then started to have similar issues to what you describe. Was OK for perhaps 20 mins but then just scalding hot air from the drivers side vent. The Audi technical bulletin fix was a heater control valve replacement at many hundreds of dollars. I eventually found a thread on repairing the valve. Not sure what system the E34 uses, but the Audi has a mixing valve just in front of the firewall which has two poppet valves (one for each side of the car?) controlled by solenoid coils. The issue is that for some reason the poppet valves end up with a tiny bit of tar like varnish on the pistons and this causes the piston to stick in the 'boil the driver' mode. Removing the tops, coils and poppet valves and cleaning the pistons (I used a small ultrasonic bath that we used to use for Kart carbs and then some Solvol Autosol) did the trick.

Hope this helps

Richard

[kiwi328i 118]

mmm, thanks for the replies guys, but if it was the heater control valve, wouldn't it just give me hot everywhere? I didn't think it would differentiate between certain areas inside the car? I might pull the heater control valve out over the weekend and hope it looks better than the one I had in my 328i which had perished rubber everywhere.

[_ethrty-Andy_ 2132]

yes very common E34 and E32 problem, possibly other BMW chassis too. replace with new, or plenty of threads about how to service them on google. Have read they can be bypassed too, but i don't see that as a solution to the problem personally

[kiwi328i 118]

Just in case someone does a search and digs this up later. I hate looking at threads that interest me only to find they had no conclusions! So I googled the heck out of this and ended up buying a heater control valve kit from fleabay.

I wrestled the heater control valve from the car, carefully pulled it apart, followed the emailed instructions, actually I didn't really it's pretty straight forward, replace the main parts, it had three o rings that didn't need replacing and I may have ended up damaging the unit doing so, they were only hose rings not any internal bits. A thoughtful and comprehensive kit I thought! especially with the instructions in minute detail. I think it was $120.00ish landed. after doing everything, whacked it back in and when I tested it! it was cold as he'll???and no hot! after checking everything proper like and pushing in the terminals all the way! I re-tested and it's sweet as! this is the way to go after had mucked around with 'good' secondhand units in previous bmws. Result!!!

[kiwi535 538]

the reason why you get hot air in some places is that onlyone side valve is stuck,and the distribution of air is not what you might expect.Esp witht automatic sytems which send air all over the place trying to cope with wildy different inputs than the system was designed for.

Thats my theory anyway

[_ethrty-Andy_ 2132]

the reason why you get hot air in some places is that onlyone side valve is stuck,and the distribution of air is not what you might expect.Esp witht automatic sytems which send air all over the place trying to cope with wildy different inputs than the system was designed for.

Thats my theory anyway

and its correct too, especially in the later E34 systems.

[kiwi328i 118]

Agreed. Knowing that it had two valves unlike some of the single valve heater control units, I thought or hoped as much. To be fair both rubber thingmewotsits were buggered equally either side. in any case I think one thing to take away is that it's probably better to reco the unit than get another secondhand one! and that secondly! there are good kits out there to cater for tight assess like myself.

[kiwi535 538]

Agreed. Knowing that it had two valves unlike some of the single valve heater control units, I thought or hoped as much. To be fair both rubber thingmewotsits were buggered equally either side. in any case I think one thing to take away is that it's probably better to reco the unit than get another secondhand one! and that secondly! there are good kits out there to cater for tight assess like myself.

thats good to know,who knows another e34 could well end up in my garagge at some time