no climate control buttons work on 300E

[WANT '71 280SEL]

I am speaking of my dad's 300E. No buttons work on it. I think that the aux. pump is bad because it doesn't seem to turn nearly as fast as the one on my '79 SD, which is a much better car if you are ever evaluating them. Anyways, even defrost doesn't do anything. The fan doesn't come on either. I think I hear a click when a button is pushed and it isn't the noise of the button being manually pushed either. Could the whole push-button assembly be bad or could I just maybe resolder it like I have heard has been done to these for other problems?
Thanks
David

[pesuazo]

Take it out and resolder all the connections for the buttons.

[ItalianBenz]

Want. How about if you put the defroster on high setting.

Sound like you have a blown 30 amp fuse for the acc unit.
does it come on intermittently. alot of times on the early cars. The blower motor units would go bad.#1 First see if you have a burned fuse. Its located near the fusebox. In a fusable link. Its a little black plastic cover. Pop it open. You should see a the fuse. almost like paper thin. Make sure it not buned or split in half. Psysically feel it or push on it and see if its solid. If it seems ok.Move on,#2 sometimes. the electrical portion of the igntion switch goes bad. turn the acc setting on high blower speed wiggle the key in the ignititon see if it comes on. If it does, you need a new ignition switch If not step #3. with blower setting still on high,wack the center console pass side,closes to the ac unit,see if it comes on,if not step #4. Remove center wood,remove Ac unit. Make sure all connections are ok,you hear a click noise you said. Sounds like the ac unit is send a compressor signal. Thats good. Meaning the unit is probably ok.
If you tinker with these cars,disconnected the black connector @ AC comressor,blue and green wire, put a test light to it. While turn off and on ac unit. If it lights up. The ac unit is ok. # 5 going to need a new blower motor. Thats the hardest of the steps, you have to remove your wiper assembly.




Hope this detail diagnostics helps you out.






guido

Yes, resoldering the CCU MIGHT fix it. But regardless of whether you fix it or replace it, make SURE that you test the aux pump for current draw. You should always do this when replacing the CCU, but especially since you suspect it anyway. If it draws more than 1.3 Amps, it will blow your CCU.

Hope this helps,

[psfred]

If you get nothing at all, check the CC fuse in the fusebox (don't remember the number). Probably cracked -- this will get you no fan, and only heat out the defrost vents while driving.

If everythings works but the fan, the most likely cause is a blown strap fuse in the little "coffin" next to the fuse box.

Heed Larry's advice about the aux pump -- I have to test mine, the CC in the TE has gone crazy (constant variations in blower speed, funky temp control, and the solenoids clatter constantly).

Peter

[pesuazo]

YES, I am with ItalianBenz. Try the wiggle trick first.

[TROVERMAN]

How do I test amp draw on the aux pump? How do I take black plastic cover off CCU? I get all the little clips off, but the the top part (where you get at the buttons) doesn't want to come off. I don't want to break it.

For all you that know about the CC of MBZ's, does the fact that I can no longer get the air distribution to change from the default (defrost) position indicate a problem with the CC panel or a vacuum connection? (Air will only come out of defrost and two vents in front (no centers for a/c) I would really appreciate the help--this is the only thing wrong with the CC, and would really like (need) to get this fixed for as cheap as possible.

Thanks

[WANT '71 280SEL]

It started working again 2 days ago! I haven't had a chance to do anything with it yet but I am going to leave it for now. It couldn't be a blown fuse if it works fine now. Maybe it is just corroded? Thanks for the advice.
Thanks
David

[psfred]

The fuses are aluminum strips on ceramic -- they can both corrode and fatigue crack from flexing when current flows -- it's very common to have a bad one that looks fine until you touch it. The aluminum strip cracks when you flex it.

If one is bad, it's wise to replace the whole set -- the rest aren't too far behind.

The blower motor fuse is not in the fuse box -- it's in a little "coffin" box close by. Pry the cover off and remove two phillips screws to remove it if bad.

Peter

[pesuazo]

If it started working again all by itself, I am pretty sure the problem is with the ignition switch.
If it stops working again, try the wiggle trick.

[ItalianBenz]

Want reason is. Too many keys on a key ring. Puts too much weight on the igniton tumbler wearing it out.

[WANT '71 280SEL]

It is just a single key. It doesn't even have a ring becasue my dad doesn't like key chains. He keeps all his other keys on a seperate ring in his pocket. How do I test the ignition tumbler?
Thanks
David

[gemoore]

I've recently had the same problem. AC/heater worked fine all winter, but then, as temperatures climbed, the AC started acting up.

I think my problem also was in the ignition switch. Today, I sprayed some electrical contact cleaner in the key hole, and followed that up with compressed air. Lots of black stuff came out of the key hole. I also thoroughly cleaned the key.

AC now comes on regularly when it's supposed to. My fingers are crossed.

You might want to try the electrical contact cleaner. I don't think it can hurt anything. It's available at Auto Zone, etc., stores.

Good luck.

[ItalianBenz]

The best thing I can tell you from yrs of replacing these. Change your elect portion of the switch. If you have mielage I would repl the whole unit with a new coded ign tumbler. Then Get a 2 0r 3 keys on a ring thats it. It will last long time.









Guido