Hi

I have noticed my ventalation/heating system (non a/c) is pretty feeble when it comes to hot air unless I get moving! At tickover from a cold start there nothing much happening, then hit the loud peddle and the flow of air is greater and the heat comes through much better, but this is also true when the engine has warmed fully (though to a lesser extent).

Can anyone tell me why?

Mike.

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1990 Euro 190e 2.0l Petrol Now Sold Maybe a w116 280se next

It sounds like you may have a aux water pump failure. This pump pumps coolant through the heat exchanger that the blower blows across to deliver heat. The coolant will flow on its own with out the aux water pump, but only when the car is moving at a nice clip (<20 mph). the purpose of the aux pump is to provide coolant while the car is not moving, so that you don't lose heat in traffic and while idling.


if the fan blows harder when you speed up, it most likely is your alternator failing. the blower runs off the battery when you idle and slows down. when you speed up the alternator gives the blower more current. your alt is most likely not dead, just having trouble putting out a decent current when the rpms are low.

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1977 280 E
1994 C280
1992 190E (sold)

"Jump in the hatch and turn on the key, pop in the clutch and let the wheels roll free"

Sounds like an issue with the battery or alternator. You have heat but the fan doesn't want to blow unless you rev the engine up. Check the alternator.

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Lenny

There are only three sports: bullfighting, motor racing and mountaineering; all the rest are merely games. --Ernest Hemingway

'10 GL550/'04 BMW 545/'99 BMW 323/'98 ML320/'87 VW GTI (race)

Cheers, as it happens I have a spare one which was overhauled recently so I'll drop that in over the weekend. If that dont work I'll look at the aux pump.

Mike.

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1990 Euro 190e 2.0l Petrol Now Sold Maybe a w116 280se next

One thing i didn't make clear, is that it is the aux pump only if the fan blows the same speed when you slow down, but no heat comes out.

if there is heat, but the fan speed changes it is most likely the alt or battery.

have fun.

I just wrestled this problem on my 280E. I also have the alt problem as well.

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1977 280 E
1994 C280
1992 190E (sold)

"Jump in the hatch and turn on the key, pop in the clutch and let the wheels roll free"

Hmmmm. this morning on my travles I was paying close attention to the heat and flow-through, its NOT related to revs. When stationary no matter if the engine was at 800 or 3000 rpm the flow was the same, put it in gear get moving and suddenly improvment so I dont see it as an alternator problem (plus I dont have any other symptoms of a dying alt), perhapes something to do with vacume is that possible?. Just had a (bad) thought, maybe the blower is dying.

Mike.

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1990 Euro 190e 2.0l Petrol Now Sold Maybe a w116 280se next

Check the fuse for the blower motor (may be in fusebox, may be separate) -- sounds as if your blower isn't running!

It's also possible that the blower speed control unit is bad, but that's unlikely.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

I suspect the control for the blower may be faulty, even on the highest setting it does'nt exactly blow you away!

Mike.

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1990 Euro 190e 2.0l Petrol Now Sold Maybe a w116 280se next

Sounds like an interesting problem now. There is this thing called the resistor bank, which compares the resistance from the temp sensor inside the car to the temp sensor outside the car. It then increases or decreases voltage to the blower motor to accomodate the cabin temp to the desired setpoint. If you notice during normal operation, when your cabin temp reaches the set point, the blowers softens to dampen the temp overshoot.

It could be that this resistor bank is faulty and sending funny voltages to the blower. This just happened in my friends Acura, and he found the resistor bank for $23 . his blower works fine now.

Locating it is tough , but it usually is under the dash near the center on either side, but i do not know this for sure.

Any confirmation of this from anyone ?

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1977 280 E
1994 C280
1992 190E (sold)

"Jump in the hatch and turn on the key, pop in the clutch and let the wheels roll free"

I believe the W201 chassis has the newer swithing unit rather than the current controlling resistors. Blower controller is in the airflow box under the blower motor itself, and is rarely the problem.

More likely the brushes in the motor itself are bad, or the fuse for the blower has failed.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Tired brushes sounds plausable alright, stuck in a fresh fuse with no effect (not that I was expecting any change).

However I did fix a diff problem when I had the ventalation/heater dash assembly apart, I spotted how to fix the passenger side heater control which was broken. The heater dial and the valve control were not linked (this had been the case since I bought the car) so the air that blew out had a fixed tepid tempurature.

Anyways I guessed how the parts proberly fixed together (not being able to see the join), and by holding the vertical control rod with pliers I managed to get the rod to click into position with the horizontal arm which projects behind the heater dial. Its hard to explain! Anyhow unlike last winter I'll have heat on both sides.

Mike.

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1990 Euro 190e 2.0l Petrol Now Sold Maybe a w116 280se next