A very common problems amongst the E32's is the inside temperature setting. While you may be able to control the temperature in one side of the car, the heat is always on full in the other side. This can be very annoying under normal conditions, but on a hot summer day...!

The root of the problem can be a great many things, like a bad rubber gasket on one of the plungers that control the hot coolant flow (about $70 to replace), but on most cars the problem and fix is actually very simple. With a bit of luck and a good eyesight, you can fix this without spending one cent.

The problem (in most cases) is this: when you turn the drivers side temperature dial, you change the resistance (in Ohms) that controls how much hot coolant is allowed into the radiator. This signal is let through a micro switch, that is activated when the dial is on full. The idea is that when the driver sets his temperature to maximum, it cuts out the exact signal and simply goes to max. resistance. Unfortunately, this micro switch gets dirty over time and therefore can not let the signal from the dial through. Result: maximum heat all of the time.

To fix this, you will need either to replace the micro switch or open it and clean the contact plates inside. Don't know if it is possible to buy a replacement switch, but if you decide to open the old one and try to clean it, you should be aware that the parts inside are VERY small. I did this fix successfully myself, but I'm not sure it's something to recommend.

Location of the micro switch: When you are turning the dials to adjust the left/right side cabine temperature and the speed of the air blower, you are turning the three black knobs you see on the photo above. To access the switch, you will have to pull out the air flow control panel from the dashboard and open it.

Word is out that resoldering everything on the control panel sometimes can help, but I wasn't so lucky. Maybe you are?