87 300D turbo - Climate Push button ques - PeachParts Mercedes-Benz Forum

a2t · #1 05-10-2007, 08:01 PM

My pushbutton seems to work sporadically. Sometimes it comes on, sometimes not.

Is there any typical wiring problems with the plugs going into the pushbutton that I should check? Last night I resoldered the pins on the plugs, hope that helps.

Problem seems to surface when interior temp gets above 90F. Go figure.

Ive already contacted Programma, they want $200 to rebuild unit. I'll go that route but I want to make sure Im not missing someting easy.

Thanks.

a2t · #2 05-13-2007, 08:28 AM

I stuck the whole thing in the refrigerator, and the climate box worked again.

Seems like if it gets hot it wont turn on the blower fan.

Any thoughts ?

stevebfl · #3 05-13-2007, 08:42 AM

What exactly doesn't work consistantly? Most functions of the push button unit aren't readily detectable.

ytr1903 · #4 05-13-2007, 08:44 AM

My 300Sd had the same symptoms. Blower not turning on when it was extremely hot out. If I pushed on the wood right next to the blower buttons, the blower would start, when cooler the system worked perfectly. I replaced the CCU and everything now works as it should. You probably have a cold solder joint in the CCU. Try the www.Benz-store in Georgia for a CCU. $135 and a 3 year warranty.

Good luck,
Tom

JFawcett · #5 05-13-2007, 09:47 AM

I am having the same problem on my 87 560SL - think it is the same push botton unit referenced in the 300SD problem.....when hot, blower is sporadic. I know the AC system is working (you can hear the compressor kick in and feel cold at the vents - but no blower).
I took out the push button unit and cleaned it up - not not really a servicable unit.....any ideas?
On internet new units are $625 at Adsit or $267 used......
Or at All European Auto Parts for $220.....can't seem to find the BenzWorld site referenced above.....any help on how to fix mine or find for less would be greatly appreciated. This "hobby" car is kiling me!

ytr1903 · #6 05-13-2007, 09:57 AM

Sorry. Here is the good link.

www.benz-store.com

Tom

JFawcett · #7 05-13-2007, 10:06 AM

Thanks. Do you think it is the unit or something that is hidden somewhere next to Jimmy Haffa's body?

ytr1903 · #8 05-13-2007, 10:18 AM

I can only tell you that it fixed my problem, which was the same symptoms as your problem. Do a search on this site for "CCU solder". That should give you more info.

Tom

JFawcett · #9 05-13-2007, 12:16 PM

Thanks....not really handy with a soldering iron....and can't seem to see any breaks in the circutry.
Probably just worn out from 20 years of operation.
I will order another one from the Benz Store and hopefully will have the same luck you had!

Thanks

John

a2t · #10 05-13-2007, 04:39 PM

Awwwwwwwwwwwwwwww man why didnt you post earlier?!@

I already spent $250 at another place on a programa rebuild with a 1yr warranty...Doh! I knew I should of waited for experience to chime in. Got a preggo wife and 3yr kid and its hotter than hell in Atlanta already.

Oh well, hope this fixes it.

The symptoms are the blower fan comes on sporadically. If there were a mathematical equation, it would be 1 / temp F (ie, the hotter it is, the less chance you have of it coming on - someone kick Murphy in the nuts for me). Ive punched the dash/CCU from every angle and nothing. The refrigerator trick seems to be only thing that works, sometimes (see aforementioned equation). If I could figure out the wiring schematic for the life of me, I would just hotwire the blower fan and we'd be all set. Apparently the CCU gets inputs from 28 different things, and also looks at alignment of planets to calculate output signals. God help the newer Benz owners...

JFawcett · #11 05-14-2007, 09:52 AM

No kidding! I am just hoping that this fixes it....really can't tell wife I have to put another grand into the car for the AC.....I have already spent a fortune on it!
On the way to dinner on Sat night, the damn AC wouldn't come on.....needless to say it was a rough ride to dinner.
I will keep posted...either way replacing the CCU does eliminate another potential problem from the system and is cheaper than taking it to mechanic. Eurocar Werk in Houston does incredible work...but incredible prices! Also, the little wheely thing was looking kind of rough.

I was wondering about the 2 big block wiring connectors on both sides of the CCU....I didn't know there was that much wiring needed to control on or off.......mine worked sporadically. On Sunday I took it out and cleaned....well I cleaned it so well, it won't do anything now!
Just ordered the new one.

Ken300D · #12 05-14-2007, 10:16 AM

While it is true that the pushbutton solder joints are the most likely to develop cold cracks because of the physical stresses on them from use - you need to retouch every solder joint on the board to be sure that they all are still good.

This is easier with the late 80's CCU because you can get to all solder joints just by taking off one cover. Earlier CCUs had more than one board level inside.

The problem I fixed in my 1987 was the A/C compressor would come on in switch positions (like OFF) that it was not supposed to function. Shotgunning all the solder joints fixed it 100%.

Your temperature-related issue could be a solder joint. That is the easiest thing to try fixing yourself. It could also be an electrical component like a capacitor going bad.

Good luck,

Ken300D

Carfax is $25 for 30 days.
Autocheck is $25 for 60 days.

JFawcett · #13 05-14-2007, 02:45 PM

OK...I have ordered a new CCU - not a bad deal, but now I am wondering if that will fix. Ken at The Benz Store in Atlanta said my problem could be 1 of 2 things. 1 is that it is the CCU - in which case, it will be fixed soon.
2 is that it is the blower motor.....neat.
Is there an easy way to test the blower motor? Can one short across a couple pins to check it? Where is the blower motor?

Ken300D · #14 05-14-2007, 03:52 PM

The blower motor is in a compartment located underneath the windshield wiper motor and assembly. You probably don't want to go there until you try the replacement CCU.

Ken300D

babymog · #15 05-14-2007, 07:30 PM

Many times a semiconductor will develop a "thermal intermittant" problem. One method of finding the offending component was to run the unit with the board open, and once it fails, shoot the components one at a time with circuit-freeze spray (used to simply be R-12, now it's propane/isobutane et al).

My symptoms ('87 300D) were the same as Ken's above, replaced the CCU and it's fine. I also noticed that the aux. pump was seized, a common culprit for toasted CCUs.

My 201 had a fried CCU also, wouldn't run the compressor at all, seized aux pump also.