Friends at the BB,

This morning is the first time this Autumn that I've needed to use the heater on my '91 240 sedan, and it appears to not be working - the fan was only blowing cool air, even after driving for at least 15 minutes. When the heater core went out on my 740 some years ago, it made an oily mess under the front driver's side floor mat. Nothing like that is happening with the 240. I'm hoping that there's any easier answer than replacing the heater core.

Many thanks for your consideration.

Most likely the culprit is the heater valve.

If you are going to open the console up to access the heater valve, you might consider replacing the blower motor also. Both heater valve and blower motor are known problems with 240s.

Replacing the heater valve is not that difficult. Much easier than the heater core or the heater fan. Clamp off the heater lines under the hood. Pull off the side panels of the dash console. Disconnect the heater hoses from the valve and the support bracket. Remove the cable from the arm of the valve and pull put the valve. Assembly is basically the reverse of removal. Put down plastic and towels or a catch pan to keep the small amount of coolant released from soaking the carpet. Takes an hour or so tops. Nothing like doing a heater fan.

Just for future reference.. what do you use/do to clamp off the hoses?

Thanks
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"Do you think that's air you're breathing now'? (The Matrix 1999) '94 940T (463K+), 92 245 (300K+), 90 740 (148k)

There is a vise-grip tool that has rounded edge jaws for that purpose. I use a normal needle nose vise-grip with a short length of fuel hose placed over each of the jaws. -- Dave

Check the coolant level. If low, top it up. See if the heat comes back.

It sounds counterintuitive but I've had this experience more than once. And if it is happening you don't want to get to the point where the coolant level is low enough for the engine to overheat. Anyway, it's the easiest thing to check.

If the heater valve under the dash is not opening you obviously won't get heat in the cabin.

If the engine thermostat is always open the coolant will not get to operating temp and you won't get heat in the cabin. What's the temp gauge reading when this is happening?


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'80 DL 2 door, '89 DL Wagon

Mr. Bulletproof: you were spot on with the low coolant level. I knew I was losing some coolant at the water pump, but didn't realize that it'd gotten that low. I filled it up, and the heater works perfectly.

Many thanks for the diagnosis.

I'm glad it was easy to get the heat back. But it is a band-aid solution, as you know. Still, you can get by for a while if the water pump doesn't get worse.

I just noticed your location. We're practically neighbors. I was wondering where you were that you didn't need to be using the heater. It has been warm this Autumn.


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'80 DL 2 door, '89 DL Wagon