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Old 10-15-2009, 11:38 PM
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Join Date: Feb 2009
Posts: 28
No heat in my 87 300E

Gotta 87 300E, running great otherwise.
Just recently it started to flicker with the heat starting up. It would flicker and intermittently turn on and sometimes stay off.
Just recently the pattern has been that the heat won't turn on until the engine has reached fully warm and stayed there for a couple minutes for the heat initiates. It usually would kick in once the engine temp sensor came up off 40.
Is it the monovalve?
I'm anticipating a bad temp sensore somewhere?
I was thinking a short but it doesn't flicker anymore...
Fuses are all new and working.
Any suggestions are greatly appreciated.
Thanks guys.
1987 300e W124 M103 My baby.
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Old 10-16-2009, 02:46 PM
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Join Date: Apr 2005
Location: Cicero, Hamilton County, Indiana about 30 miles north of downtown Indianapolis
Posts: 2,613
Can you make your post clear?

What "flickers"?
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Old 10-16-2009, 08:09 PM
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Join Date: Sep 2009
Location: Great State of Texas
Posts: 440
Just a guess, but doesnt the car get its heat from the engine? On almost 99.9% of vehicles (including new cars), the heat comes from hot coolant going through a heat exchanger in the air distribution system, and coolant doesn't start moving until the thermostat opens up...

Some cars do have electric heat (I'm just learning about MB's), but you probably won't get heat until your engine is up to temp.

If you have auto climate control, you might try running the wheel up & down a few times to clean the contacts.

I'd also like to know what's "flickering". If the engine isn't up to temp, the climate control system might be turning on & off until it starts getting hot air...
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Old 10-17-2009, 03:42 AM
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Join Date: Feb 2009
Posts: 28
By "flickering" I meant that when the engine is cold and starts to warm up, the blower will turn on and off in rapid sequence like there's a short when the cabin heat is engaged. Just recently, the blower won't kick in until the engine has been at optimal operating temp for some time. It used to kick in when the coolant first circulated through the air distribution system. I know the coolant is coming through because I can feel it radiating (minimally) with my hand up against the vent. It just takes a bit for the blower to start circulating air over it and out the vents.
I'm wondering if I have a bad temp sensor somewhere...
I've tried the rolling of the wheel, and tried other functions. None work until the engine reaches a minimum of 40 degrees.
Thanks for the input!
1987 300e W124 M103 My baby.
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Old 10-19-2009, 12:51 AM
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Join Date: Oct 2009
Posts: 6

check the fuse in the engine compartment for the blower motor. this fuse will fail and can be split even though it looks good. take a small screwdriver and see if it will seperate. if it does then replace it. i believe it is a bi metal 30 amp fuse. very cheap to replace. if it is ok also wiggle the ignition switch. sometimes these will fail and cause something similar. hope this helps
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Old 10-23-2009, 11:37 PM
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Join Date: Feb 2009
Posts: 28
Already had replaced the fuse and the tumbler was replaced in the ignition about two months ago...
Still having the problem.
I appreciate your input. Any other ideas?
1987 300e W124 M103 My baby.
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