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1983 300CD
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136 Posts
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I'm in the process of trouble shooting my AC and climate control system and started looking into the blower motor tonight.

The blower motor spins fine when it gets a signal, but it seems to be getting strange signals from the ACC. I unhooked the blower motor and just tested the voltages at the blower motor plug. With the car off, but the key in the on position, I started with the ACC completely off. The only button that results in a voltage at the blower plug is the 2nd from the left (up and down arrows). None of the other buttons sends a signal to the blower motor. However, after the 'up and down arrows' button is selected, subsequent selections of any of the other buttons maintains the 12V signal to the blower motor.

In other words, from an ACC completely off position, none of the buttons works except the 'up and down arrows' button. Once the up/down button is pushed the first time, now all of the other buttons show a constant 12V reading.

If I turn the ACC completely off again, I must repeat the process of hitting the up/down button first before the other buttons start to work.
 

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Registered
1985 Euro 300TD Turbo, 1983 Euro 300TD turbo, 1979 Euro 240TD and 1981 300D converted to euro.
Joined
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2,700 Posts
Your acc unit is at fault. Either a good "known" working unit or have it rebuild by someone that will use good quality parts.

!k was the last price i was quoted for a factory dealership part.

About $220.00 for one from programma with a "core charge", which is made in china and lasts a very short time.

Good luck.

Also for in the future if you have any ac compressor only problems look to the huge relay in the engine bay. 85 only part that likes to die a lot
;)
 
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