w124 blower resistor heat sink replacement: now fan inop.
 

Hi All--

Car has been in the shop for a bit. I replaced the heat sink compound for the blower motor resistor as it was dried out and non-existent.

Now, I can't get the blower motor fan to operator in any fan speed.

CCU fuse 7 is good. The heat control changes the temp of vent air and placing the CCU in defrost causes the A/C compressor to engage.

I haven't checked any strip fuses or wiring but no clue what would have changed.

Any clues?

The blower is fed from either fuse 12 or an external fuse on the shock tower.

There was an engineering change to remove the 25 A fuse 12 and use the external 30 A strip fuse pretty early in 1987 MY. So if you have an early 1987 with fuse 12 you want to find the strip fuse holder and install it. It just goes across the screws for fuse 12 in the back of the fuse box, and of course don’t install a cartridge fuse in 12.

Wait just saw your sig, you have a 95, you will have the strip fuse. Check for micro cracks, they can look good and even ohm good cold but open up under load.

The ‘resistor’ in a 124 is actually a switching transistor controller that pulse width modulates the voltage to the motor to regulate the speed.

Thanks. I will check. I was running the batter down often when adjusting the sunroof.

I cranked it over and it fired up but barely from a low battery, directly after, the fan wouldn't come on.

I will check the strip fuse. I wonder if I damaged the CCU with the low voltage.