I have heater problems with my 95 E320. It makes some noises, acts unpredictably. I checked the aux pump and the amp draw seems to be ok (960 milliamps). When doing that, I noticed that the whole pump/valve assembly was very hot, and the valve was slapping on and off, sending surges through the coolant loop. Is this symptomatic of the pump needing to be replaced, the push button unit bad, or something else?

Robert:
The pulsing is normal, that's due to the watervalve opening and closing, so now you also know the valve is working OK. This has the newer style valve, it's pretty dependable, no rubber bellows to rip like the old style valve.
Possibly you are low on coolant?
Other than that, the first few things to think of would be :
1.intermittent loss of voltage, maybe a crack in a fuse causing this?
2.interior temp sensor bad
3.pushbutton panel

Unsure what the noise has to do with it, unless the low on coolant is true, and maybe it gurgles due to air in the coolant stream?
Does the noise correspond with when you have problems? Just what is the exact complaint, that the temp fluctuates or what? Or is it a fan problem, or is the air coming out where you don't expect it to? What does the noise sound like?
Gilly

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Took the car out to the movies tonight. The heater seemed to work ok on the way there, except for making noise. The predominant noise is like 'tinkling china' as my wife describes it. The other major noise is a vibration sort of like a hard drive running on a computer. Every once in a while there is also a groaning like a duct door opening or closing too slow or too tight.
On the way home from the movie, I couldnt seem to get the heater working at all. (although I could feel a bit of hot air coming through the defroster outlets when the car was moving). No matter what position the buttons were in, whether the fan was on high or auto, nothing made a difference. I pulled in the garage, opened the door and went to pull on the lever to open the hood, and all of a sudden the fan came on high, blowing hot air.
I did check coolant level and it is halfway up the fill reservoir, so it looks ok.

Robert_
If it just happened that one time, maybe somehow ice got built up in the blower case? Not really sure, the noise descriptions don't sound familiar to me, and I've heard lot's of wierd noises out of these cars. See if it reoccurs, but in general wierd noises combined with no or low airflow would point towards a blower being blocked or inop, since it was making these noises, i'd assume it was blocked by something in the blower case.
If you hit the "O" button did the noises stop?
Gilly

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Yes, the noises stop consistently when the 'O' button is pressed, so they are definitely heater related. Wasnt just this one time, but this problem has been going on for about 10 days. I checked for cracked fuse in the heater related fuse (#7) in the fusebox under the hood and it is OK. Noted that the blower fuse is located elsewhere, but couldnt find it. Could you tell me where it is?

Also, since I bought this car about 2mos ago, it has made a whirring noise on start up that goes away within about a minute. I thought it was normal, but now I am wondering.... I know that the car had the head gasket replaced while it was at the dealer between the time that it was traded in and the time that I bought it. I am wondering if there could have been some debris introduced into the cooling system at that time and that could account for the whirring (debris hitting the water pump) and the noises and problems in the heater? Would the fan blow if the heater core was temporarily blocked by debris? Or could debris mess up the coolant temp sensor fooling the blower into thinking the coolant is too cool for the fan to operate?

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If you hit the "O" button did the noises stop?
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Gilly:

What is usually wrong if the noises does not stop once the "O" button is hit?

The ACC on my 87 300TD has some issues. If I hit the "O" button, it still blows a minimal amount of air unless I keep the "O" button depressed. After I release, it will blow some air again after 5 - 10 seconds.

Thanks.

Robert:
It really sounds like something is going on with your blower motor. If the blower motor runs, it wouldn't make sense the blower fuse as a problem. The fuse is a strip fuse. The little fuse case is by the left (drivers side) shock/strut tower under the hood. It's black plastic and the top of it you squeeze a little and it flips to one side, you'll see one wire on each side of the black box, has a couple phillips screws holding it in place.
See if the whirring noise on startup goes away if you push the "O" button before starting the car, I'm still kind of thinking the blower motor is the problem and is noisy when first started, seen this complaint before.
Lets see, what else did you want to know:
The debris hitting the innards of the waterpump making a noise-possible, never ever heard of it before and I severly doubt it, but possible I suppose. Sure wouldn't think a noise like this would be described as "whirring" either.
If the heater core were blocked by debris inside the cooling system, it would only affect the flow of coolant throught the core tubes, not the core fins, which is where the air flows through. So, no, by your line of reasoning, debris in the cooling system by the head gasket job, it would not affect the fan or amount of airflow to the cabin, but could affect the temp of the air by plugging the core tubes only. If the heater core fins became plugged somehow, like by a heavy dust accumulation, it could hinder the airflow, but I've never heard of this. I've heard of evaporator cores plugging up due to freon leaks causing an accumulation of refrigerant oil and then collecting dust and clogging the fins, this is all a different topic though. Also the evaporator can ice up for various reasons and stop airflow, this happens usually in the summertime due to high humidity levels.
Based on all the info I have, I would say the most likely cause for the problem is a bad blower motor, possibly too much axial play in the motor shaft allowing one of the fans to hit the blower case.
The fan is buried under the wiper assembly. It has a central motor with a "squirrel cage" type fan on each side of the motor, running on a common shaft.
Bo:
Where is "western Michigan"? When I think about it, I guess you could consider the U.P. as "western" Michigan as well, or are you in the lower peninsula on the western side? (just curious, I love the U.P.)
If you push down the "O" button, it should stay down and shut off the system, you shouldn't have to hold it down manually. Sounds like probably the problem is a mechanical defect in the push button panel.
Gilly

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Where is "western Michigan"? When I think about it, I guess you could consider the U.P. as "western" Michigan as well, or are you in the lower peninsula on the western side? (just curious, I love the U.P.)
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Right, Gilly, UP is beautiful. Western Michigan nomally refers to the area in the greater Grand Rapids. Actaully the most western part of MI is in the UP, right above your state of WI.

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If you push down the "O" button, it should stay down and shut off the system, you shouldn't have to hold it down manually. Sounds like probably the problem is a mechanical defect in the push button panel.
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You are right. There must be a mechanical problem in the push butons. The problem is not that big to bother me now. But someday I will take the poush button out and take a look.

Thanks.


Bo

Thanks, Gilly. I found the blower (buried is right!). The motor looked as though it had water on it at one time and the shafts were rusty. The shaft felt a bit tight when I tried to rotate the squirrel cages, so I started the car and turned the heater on. The fan didnt move. I gave it a push and it cranked up to speed. So, I guess your diagnosis is right, it is the blower motor. I will call MercedesShop in the am and order a motor and a cabin filter and I hope I'm good to go!