Poor heating

[rodbaxter]

I have a '95 E320 and the engine temp gets to 80C and stays there. Inside though, it doesn't seem to get very warm. I worry about how it will feel when it really gets cold. It does that in Saskatchewan! Anyone else with cold weather heating experience?

[AusMBtech]

You need to find the heater circulation pump (it's in the heater hoses leading to the cabin) and make sure that it's operating when the heater is on. If it isn't working then it will have a big effect on your heater operation.

[rodbaxter]

I have talked to the mechanic and he thinks we should start with a flush and replacement of the coolant. Using Benz flush and coolant of course. I get some heat but my fan never goes off high when it is in the auto position because it never gets hot enough inside the car. He says the auxillary pump is only noticeable at idle, at speed the water pump does all the pushing.

What do you guys think?

[jlomon]

My first thought was the thermostat might be stuck open. 80C seems like an awful cold running Benz.

[rodbaxter]

Seems you were right AusMBtech. My indy flushed coolant system with the citrus flush, filled with MB coolant and it still doesn't get very warm. He says it is the Acc Mono Valve and the new valve is $380.00 Cdn.

Does this sound right? Is this a common fail item? It seems every time I take it in it's $500!

Any help would be appreciated.

[jbaj007]

$184.00 USD from FastLane

[AusMBtech]

with the ignition off, press the "rest" button on your a/c control panel. Then go into the engine bay and feel the circulation pump with your hand......you should feel it operating. If you do then the fault isn't the pump, but it might be the heater valve. If it isn't running then check if it's getting a voltage at the motor (if there's voltage then it's the motor at fault, if not then the fault may lie further up the electrical system.

It pays to do through checks before starting to replace components, it's cheaper and more accurate in the long run.

[rodbaxter]

Is the heater valve part of the module? From the picture above it looks like there are 2 parts there. I would still have to buy the unit right?

[Benz300]

I am experiencing the same situation with luke warm air inside the cabin.
before we go ahead and start shelling out cash on all sorts of monovalve and other repairs, the question I would ask you is, how is the inside temprature when the eng temp. does infact rise above 80deg. momentarily, that is when at a stop and the car is running etc.
I have noticed that the poor internal heat on my 260E is due to the colder running temprature of the engine itself that is 80deg.
the internal heat is perfectly fine when the car is at a stop and engine temp. is around 90deg.
find out if that's the situation with your car as well and please post results.

[rodbaxter]

You can feel the pump running with your hand. At least, it's vibrating. In reply to the above reply, I have recently driven in 2 other E class cars of my vintage and their engine temp were right around 80C and they had lots of heat in the cabin.

I was told that only the '94/95 E's have a combined valve + pump module, on the earlier cars the valve was seperate and much cheaper to replace.

[AusMBtech]

I'm not sure exactly which year models have a combined pump/valve unit and which have seperate units, I usually just look at the car.

Have a look and see if you have a combined or seperate pump/valve units.

Your next check is to run the engine upto operating temp (with climate control on min temp, no a/c. Put one hand on each side of the heater valve. get someone else to turn the heater temp on full (with engine running) and see what happens. It should get hot.

The 3 remaining possibilities are faulty control unit, a problem with the ventilation air blend system (blend hot and cold air) and a faulty heater valve.

[kidMoBile]

Hi:
I have a 95 wagon and have the same complaint. Thanks to everyone for the above tips; I'll check these components first. I would just add that when I put defrost on with the temp wheel set as cold as it gets, the air is hot coming out. I've read that this condition is indicative of a faulty climate control unit, as MB designed the defrost temp to default to hot when there's a problem with the CCU. Just wondering if the others with this lack of heat complaint are experiencing the same condition when trying to defrost with cold air?
brian

[ejsharp]

My guess is the control module... very common problem on your car.

Can be easily and cheeply fixed with a spot of solder. Look up my old posts to find out how to make the repair yourself.

[Jim Anderson]

When was the last time you changed your's? I think they should be changed every couple of years, I've seen them do real funny things, besides sticking shut and