Climate control/blower motor issues.

[vwbuge]

My son said the blower quit working in his 300SD. I found a blown fuse but it was one of the cheap plastic fuses so I blamed it on the fuse and reinstalled one of the original ceramic fuses. It was working again. We did some maintenance on the car the other day and we discovered the blower is not working again. Checked the fuse and it looked ok. Tried another fuse just to be sure and still not working.

Next I guess we will pull the climate control unit and check for power in and out? Is there a relay somewhere I am missing?

[mike280]

its most likely the aux water pump failed which in turn blew out the trace on the ccu.

HELP!! Smoked my second CCU control...

[ykobayashi]

I just figured mine out today on my SD. My blower was getting intermittent and not starting up when I started the car. When I restarted the car it would run.

I thought it was a bad blower. I replaced it with a URO blower and it still had the same issue. My old blower was very tired but it still works.

Somehow by luck I realized I if I instead didn’t restart the car and rotated my key backwards a bit the fan would run. So I crank, I don’t get enough snap back on the key. During cranking the fan turns off. When the key snaps back to the run position the blower still doesn’t start. If I rotate my key counterclockwise just a nudge the blower fires up.

I looked at the wiring diagram for the SD and the blower power is routed through the ignition switch on its own circuit. Basically it shuts down when cranking and turns back on when your key snaps back to run. Mine need a little counter clockwise nudge for some reason. I’m putting a new switch on order.

I cannot decide if I want to cheap out and get a URO or get OEM. This car doesn’t have to last another 40 years.

On my car the blower would come on when I put the key into the run position but it would shut off after starting. That was the giveaway that it was a switch issue.

You may have a bad fan controller box. That’ll be up under the passenger kick panel next to the hvac box. It’s a black box the size of a pack of Dunhills.

[Diesel911]

Just in genral. As the blower is used it gets crud inside of it and the bearing lube dries up. When that his happening, the blower starts bogging down and it takes more amperage to get the blower going.
People have also had worn out motor brushes.

The 300SDs from the 1980's have a factory add on fuse and wire updated. But if you intend on using the same motor you ought to check it out and clean it out and re-lube it.

That is a similar issue to the window motors.