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Old 02-04-2002, 02:09 PM
Posts: n/a
'83 300D -Blower dead some mornings

On some mornings the heater blower on my 300D will not start up no matter which buttons I push. It seems to me a motor either is good or bad but not
intermittent like this.

Is there a relay that could be sticking on cold mornings, or is there vacuum involved?

If it is the blower motor itself, do I get at it from under the dash or from the firewall,
and how big a job is it?

I also have a problem directing the heat to the floor. It seems no matter which button I hit the heat gets distributed evenly among the floor, dash, and defroster outlets.

Any thoughts?
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Old 02-04-2002, 03:44 PM
Join Date: Mar 1999
Location: Tucker, Ga USA
Posts: 12,153
Almost all MB's have a cold engine lock-out of the blower motor! This keeps you from freezing yourself until the engine warms up.
IF you ask for heat & the engine is cold the blower isn't susposed to run. TRY asking for A/C by rotating the temp wheel to the MIN detent & then see if the blower will work. OR even defrost.
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Old 02-04-2002, 09:50 PM
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Join Date: Jan 2002
Posts: 17,492

I have some oddities with my blower also. When the engine is cold, it only blows on defrost. When the engine is warm, it will only blow on the other settings if I first turn it on with the defrost setting. Once the engine is warm and I shut if off and start it again before the engine cools off, it will run in the other positions without first beginning with the defrost. I suspect it has something to do with the sensor that keeps the blower off until the engine is warm.
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Old 02-04-2002, 11:32 PM
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Join Date: Dec 2001
Location: Chicago
Posts: 100
It sounds like my problem.

My blower would not work if the weather is cold and it only worked when it was a bit warm outside. Replaced the thermo, the monovalve and still no go. Finally found out that the ignition switch was the problem. Since the connecters on the switch are made of metal (of course) then once cold the connecters will not make contact and the blower did not have any juice. And once warm temp is in the air the metal will expand therefore making a connection and I have a blower that work.

Here is a way to check that, you need a test light. Open the fuse box when the blower is not working. Remove the fuse for the blower. And then make contact on the terminals of the fuse holder to see if the light works, if the light does not come on from either side of the fuse terminals you are not getting juice to the blower or the blower relay. Try the light from another fuse just to make sure it works.

Good luck and be careful not to short anything out.
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Old 02-05-2002, 07:11 AM
Posts: n/a
No blower on Defrost either

On mornings when the blower doesn't operate, it
doesn't work on defrost either; I'll have to try
adjusting the temperature wheel to cold to see if that helps the next time the blower goes on strike.

I'll also check to see if I have voltage at the fuse next time. I have had the ignition switch
temporarily jam a few times lately. All other
accessories work, the rear defroster, signals,
and radio...
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