Heat problem...please help

[1990m3]

I've had and E30 M3 for about 5 years now, and I just picked up a '91 318is today. I drove it home about 450 miles and found out I have a problem with the heat in the car. No matter where the thermostat switch is set the blower only blows very hot air, like it's turned all the way hot. If it's turned all the way cold, it will blow cold air, but if it's only 2mm away from all cold it blows hot as hell.

Any ideas?

also, the temp. gauge reads between 1/2 and 3/4 mark the whole time. Never gets any hotter though and never over heats. I only know the S14 motor, this is my first run in with the M42, and I've never experienced the interior temp switch issue I'm having. Any help is appreciated.

Thanks

Dave
'90 M3
'91 318is

[Waynegro]

I would flush your radiator fluid (check for clogs), replace the T-stat, take a look and see if your fan clutch is working, and same goes with the radiator fan. Anyone of those or a combination could be the problem. I have had to replace all of the above to get my car to cool down. Best of luck and there is a ton of info under the search feature.

[PeaveyBassist]

heater valve. Check that. It is what controls how much coolant goes through the heater core. It might be constantly letting coolant through there. Also the thermostat on the center console. Check that too.

Will

[AdamF 88iS]

Check that you have power to the heater valve. It needs 12v to close. No power allows it to open and have constant heat. If it has power then it's probably stuck open.

[1990m3]

where can I find the heater valve?

That sounds like what I should look for first. My fan clutch works fine, I think the aux fan is broken, but that doesn't explain the interior heating situation.

[rs4pro3]

Driver's side floor board above the gas pedal

[BS87]

Check that you have power to the heater valve. It needs 12v to close. No power allows it to open and have constant heat. If it has power then it's probably stuck open.

I thought it was controled via bowden cable like the rest of the HVAC stuff?

[rs4pro3]

nope the valve is electronic

[1990m3]

thanks, I'll check it out tonight!

[UNHCLL]

Dave-
You'll have to remove the center console to gain access.
Its a cylindrical "box" mounted on the coolant hoses (metal) coming through the firewall. You'll see one small electrical connector at the top.

Good luck!
And when/if it comes time to change replace it, make sure you cover the entire floor/tranny tunnel in the drivers footwell with plastic.

Chris

[1990m3]

thanks for the tip chris, I'll test it tonight and see what I come up with. That problem needs to get solved ASAP,

anyone got the part #??

[rs4pro3]

http://www.realoem.com/bmw/showparts...23&hg=64&fg=15
#7 on that diagram

[sepehr]

The heat isn't controlled only by the heater valve. There is also a flap connected to the temperature knob that controls the amount cold outside air that mixes with the heated air coming through the core.

On/off heat could maybe mean that the cable controlling the flap is loose? The lever the other end of the able is attacked to is on the passenger side of heater box. You can see it from the little gap between the glove box and centre consul by the passenger's feet.