Where is the heater contol valve on a 240?

[dmg4]

It's a 1992 240 that has plenty of heat; for which I am thankful this cold holiday on the highway. The only problem is that the amount of heat is minimally adjustable. Sometimes, if I continue to quickly move the lever to the left, the heat does decrease substantially, but not always. I assume there is a cable from the slider to a valve somewhere that is loose, detached, etc, but where should I begin looking, or is this a vacuum control problem?

Temperature gauge climbs quickly to dead center and stays there, so I don't think I'm dealing with a radiator, heater core or thermostat issue.

[russellengineering]

Hi DMG4,

I have a 93 940, but I think we both have the B230 engine so our heater control valve should be in the same place. If you are at the front of the engine and look to the right of your throttle body, you will find it buried below and to the left of the master cylinder.

It has a coolant line in and out, and a vacuum line. Vacuum does open and close it, so your theory is good. If you have never changed it, my word of advice is to replace it just as soon as you can. If will eventually break and dump all your coolant about as quick as you can read this response.

Good luck,

Dave

[dmg4]

Good morning,

There seems to be some confusion among sources about the exact type of control system used in the 240 during transition from 1991 to 1992. I've read that the controller is located above the gas pedal, on the firewall inside the engine compartment and beneath the radio. Also, that it is brass, or plastic, and does, or does not incorporate a mechanical thermostat of it's own. I'll check under the master cylinder. Maybe that's where it's hiding.

As I recall from before the problem in the present 1992 240, and my vague and foggy recollections of my 1989 240 from long ago, are that the heat is set to a level, and that's what you get. There's no evidence of a thermostat refining the heat output through any sort of feedback, either controlled by vacuum, electronics, or otherwise. It seems to be operating like a simple flow control valve: more heat, more coolant....less heat, less coolant. The driver is the thermostat. Correct?

[billofdurham]

The heaters on the 240 and 940 operate in different ways. On the 240 the control valve is on the side of the heater unit as in the attached:

240 heater.pdf

(112.12 KiB) Downloaded 298 times

It is item 14 and is cable operated. The cable may have worked loose but I would suspect that the valve itself is not working as advertised as you can, sometimes, get it to work.

Bill.

[dmg4]

Finally pulled the drivers-side trim panel on the console and found the valve. The cable seemed was operating the lever, so it seems it's attached at both ends. However, there was about a bushel of maple tree seed pods and leaves in there. After about 30 minutes of poking around with a shop vac necked down to 1/2" plastic tube, it was all cleaned out. Oddly enough, now everything seems to be working. We'll see over time if this was a permanent fix.

[billofdurham]

Thank you for the update.

Bill.