Climate Control Unit oddity
 

In the '83 300D the climate control unit acts a bit weirdly.

If I select EC the fan does not turn on but if I select defrost then EC the fan runs.

Now I haven't gotten into the dash yet to verify that the air sampler tube is in place, I hope it is. I did find the air sampler grate thing inside the mess of wires and vacuum lines while installing the radio last week (car has a dash cap).

So, does anyone else thing my CCU is acting out of the ordinary?

I had a similar problem with my '85 300D-T. The cause was worn blower motor brushes. When the brushes are almost worn out, the springs no longer press the brushes against the commutator with enough force to run the motor at the middle speeds available under the "EC" programming. Pushing "Defrost" runs the blower at high speed, delivering full battery voltage to the motor. Once the motor has been "kick started" it will continue to spin at the lower EC voltages. It may be possible to replace the brushes, I recall many brush discussions here some years ago. In my case, I replaced the motor with a new one. A good used motor might also be an option.

Jeremy

I actually have the brushes replacement kit. I wound up replacing the entire blower as someone I know was parting out their car. If you decide to tackle the brushes only maybe we can work something out. As long as your commutator is in good shape the brushes route is feasible I think.

Mine's been doing that for about 4 or 5 years.

I'd rather replace the brushes since a lower is expensive.

That's a pretty common condition. Different modes utilize different relays in the PBU to power the fan.

Uh, you may find that it is not. Let me think...

I have been wresting with ripping a blower motor out of that parts car.

Joe, if you want it and feel like coming back to remove it ( it's wasn't cooperating months ago and now I have lost interest for obvious reasons) it's yours.

Rick

When you hit defrost, the PBU signals for high speed on the blower.
I'd suspect the blower regulator.

Jim

Did you notice that the blower continues to run in other modes once started in DEFROST? How does that happen if the blower regulator has failed?

I'll just replace it with some hose. I need to swap mono valves too.

Is that easily replaced? Same thing with the brushes?

I cannot recall my w123 I had but I dot recall having to hit defrost then ec

If the fan runs and changes speeds in modes other than defrost, the regulator is not the problem. The likely problem is a relay in the PBU. Believe it or not.

Sorry for jumping in or even hi-jacking this post. I am having something similar, it's either way too hot of cold. When I set the control just before the red area to warm up the cockpit, and when I move it to the white ranges around the 22 or less, it cools off realy fast.

Where or what can I look to atr to give me the in between temp? Thank you.

I had two or three PBU's when I had my w123 and of course I sold them all off once I got rid of it.. drat!

Looks like I will be on the look out for another good unit