Heater is always on - help

[randoms]

Hi Gang.

My 1993 e34, manuf 08/93, 5spd, std hvac, is cooking me alive. Not really. But the heater will not turn off. The fan works fine and is properly controlled with the fan dial.

Once the car is warm there is always heat coming from the foot vents on both sides regardless of the temp dial positions.

AC seems to work fine.

Anyone know what might be causing this, or how to troubleshoot it?

Thank you!

[632 Regal]

There is a coolant control box for the heater under the hood in front of the driver position (on a V-8).

These can clog and fail, in default mode it is supposed to be open to allow heat into the cabin. If not obstructed (like in your case) it will pump hot water.

Check the voltage at the box. Need to remove the clips under the cover if the voltage is there. They are exactly like old GM door handle clips. Might need a mirror to see where to push. Take that cover off and then check into it.

[randoms]

So, if I see voltage at the wires, then it's likely stuck control valves in the heater control unit?

[shogun]

The heater control valves are engine room left side close to the firewall under a black plastic cover, one for the left side, one for the right side. Without power they are always open. But if they are clogged, even power will not help. See my website, there is a detailed write up and lots of pics how to open and clean stuck heater valves.

Here a video by John where he cleaned them after I gave him some advise
Rebuilding Heater Valve in my E34 525 - YouTube

[randoms]

Thanks guys. Voltage is present on both pins at the control valve. I'll watch the vid and maybe dig in this weekend.