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1990 300e Blower/Fan problem (running only when car is OFF)

1144 Views 5 Replies 4 Participants Last post by  Julian0922
Hi, I did not find an answer after searching for a bit, so I have to open a topic and hope somebody can give me at least a hint:

I own a 1990 300e and the blower fan ONLY works when the car is shut off, as soon as I start the car the fan stops running....

What might be the cause? Battery, the ghost in the machine or...:surrender:? A shortage I would exclude, because otherwise it would do it only sometimes, but it does it EVERY time...and with that I mean hundreds of times. Just that in the autumn and winter a working fan is necessary up here...(WA)

Thanks in advance for the help.... :bowdown:
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I believe macdrone knows what your problem is and has the solution based on your first post. It's probably the tumbler aka ignition/starter switch; although, it could be the wiring going to the switch.

And now of course there may simply be too little power to run it. When the car is running what do you have for volts on the battery? It should be minimum 13.2 volts and not exceeding 14.2 volts.

That circuit is hot in run. That means that when you start the car and let go of the key then the circuit should be hot. That happens to be the same position you say the blower works now except it only works there before you turn it all the way to start. So that is why it seems to be the switch (or the wiring to the switch).

The hot wire goes from the ignition switch to the fuse box and when the ignition/starter switch is turned to the correct position it makes the circuit hot. It's probably the tumbler aka ignition/starter switch.

And it is a pretty simple circuit comparatively speaking; there is the fuse, a ground W1, a connector, the blower control unit and the fresh/recirculate air switch S24: ACC Power Distribution

W1 Main ground (behind instrument cluster) Behind left side of instrument cluster 235-5

X64 Connector, blower speed control/interior harness Above and rearward of brake booster

S24 Fresh/recirculated air switch Center console, above radio
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