heater/climate control issue

Gene Wilkes · 10-27-2007, 05:00 PM

I've read thru the threads and can't find my issue. All lights and fans are working and everything appears to be ok but my heater/climate control seems to have a mind of its own. If I turn the heater controls (dual) on and direct the heat to windshield or any of the possible settings, it works fine for a while. The problem is that the temp control doesn't seem to stay set. If the temp is set at 68 degrees it will maintain until suddenly it goes to maximum heat for maybe a minute. Long enough to let you know it's not working correctly. Any ideas? Car is 92 325is.

Jeron · Jeron's Garage

The two most common problems are the final stage resistor and a capacitor on the climate control board.

The final stage resistor only effects the fan speed. did you read the posts on the capacitor problems.

Gene Wilkes · 10-28-2007, 06:20 AM

Yep! Read everything i could find both here and on bimmerforums. No issue with the fan, it blows fine. Issue is the sudden change in heat!!

jphaymond · 10-28-2007, 12:14 PM

It might be your water valve. Part number 1 @ http://www.realoem.com/bmw/showparts.do?model=BJ63&mospid=47475&btnr=64_0126&hg=64&fg=18
I've got a 95 325 convertible and the valve is stuck open. Blasts me with heat whenever I select the floor position for air flow. It's not a cheap replacement though. That's why I've been living with it.

Gene Wilkes · 10-28-2007, 03:56 PM

jphaymond,
Do you know where this part is located? Under dash or hood?

Jeron · Jeron's Garage

I thought your problem was electronic. Meaning the display goes to full hot periodically.

The heater manifold/valve is under the hood, on the firewall, under the intake.

Gene Wilkes · 10-29-2007, 05:44 AM

Jeron,
My dual heat controls are numbered round knobs. i know there are lots of variations of these units.

Jeron · Jeron's Garage

Ok, so you have the dial set to cold and sometimes it blows hot.

My guesses would be:

1 heater valve
2 heater temperature sensor
3 bad switch at the knob

The valve has two solenoids so I think if one is failing it should only effect one side.
A bad switch would also only effect one side but since it is working sporadically I would think turning the knob a few times would sometimes clear it up.
A heater temp sensor would cause both sides to fail and blow hot at the same time.