anybody ever resoldered AC Type II Control Unit? - PeachParts Mercedes-Benz Forum

tschepplmasta · #1 06-30-2002, 05:07 PM

Hi!
Would desperately need tips how to resolder
A/C Climate Control of a 1980 300D!
Any ideas?
thanks so much in advance,
T.

Benzmac · #2 06-30-2002, 10:21 PM

You have to take it out, take it apart, then use a solder gun to heat up the old solder and add a little new to it.

tschepplmasta · #3 07-02-2002, 02:07 PM

I'll try that!
Thank you!

#4 07-02-2002, 05:16 PM

Have you ever done circuit board soldering before? If you have, it will be no sweat to follow Donnies instructions. If you have not, you need the right soldering iron, about 25 to 40 Watts. Don't try it with a big soldering gun or some such. Use the solder to make the heat flow, then get off of it, once the solder flows. If you use too much heat or heat for too long you can raise the traces, ruining the board.

Good luck,

tschepplmasta · #5 07-04-2002, 05:56 PM

hi larry,
thanks so much for your input and i'm really proud to hear from
you, the king of the diesels!!
some short questions for you, as i have no experience with
resoldering so far:

- is an 25W or a 40W soldering iron better? i don't wanna ruin
anything...

- to describe my situation: my acc didn't work at all (1980 300D),
but i fixed all the vacuum nightmare and made it all work, but:
the auxiliary water pump won't come on in heating mode, but
i need heating as well (in winter at least). the pump itself works
great, and reading all the postings in the forum i figured out that
a damage in the climate control unit is the most likely problem
here. i attatch a picture in this mail, indicating the 5pushbutton
switch, or the electronic device behind it, asking you: IS THIS
THE PART WHICH IS TO BE RESOLDERED? any comment on this
would be just fabulous!

anyways, i am little afraid - not of all the work to do - but of
ruining anything that i've already fixed. everything works just
great, besides that *** aux. water pump, but maybe you know
what to do best....

thanks so much in advance, i'm looking to hearing from you!

best regards, t.

#6 07-05-2002, 02:25 PM

I'm sorry, but I have little familiarity with the 123 automatic climate control systems. The 124 pushbutton unit can often be repaired by simply reheating the solder joints ON THE CIRCUIT BOARD.

My chmiming in about soldering was from my old electronic bench days, simply as a warning in case you are not familiar with circuit board soldering. A 25W or 40W will work okay. I would not recommend soldering anything that is not meant to be soldered.

Sorry I can't help any further.

stevebfl · #7 07-05-2002, 03:06 PM

Your car doesn't have the pushbutton controller that responds to resoldering. The parts in the picture almost never go bad. The push buttons only control vacuum on that car. The electric switch is for the compressor.

On your system the aux pump only runs when the temp is below 50 something. It is not necessary for heating unless very cold. The main heater control is through the servo.

Does the airflow from the center vents discontinue when you run the dial to full heat? If it does the system is moving (not moving is a common problem). If it moves but doesn't give heat the water valve portion is not working, try the defrost position to see if the thing can possibly heat. defrost is full heat with no decisions made.

If the servo isn't moving the amplifier is often the problem. You should be able to hear the servo working with key on engine off. have some one move the temp knob all the way cold then hot with plenty of time in between.

tschepplmasta · #8 07-19-2002, 04:18 AM

Steve,
thank you so much for your expertise!
Unfortunately, it took me such a long time to re-test the whole
heating behaviour extensively, but that's what's happening:

First of all, I'm glad that the switch just controlls the vacuum lines
and almost never goes bad - thank you for letting me know!

It never was below 50 degrees, so - as you say - it's normal the aux water pump never switched on - happy to hear that it's normal.
I'm pretty sure that the servo works, because it's new and I can
hear it work if I open the hood and listen very carefully with my
ear close to it.

If I put the dial to max. heat, the center vents still will blow air.
Air is coming from all air outlets, including footwells.
after a few minutes, the air gets warm, but on the passenger's side only, and on my side it will stay pretty cool, as if it was fresh air coming from outside or so.
What does "system is not moving" mean? Is this a major thing
or easy to fix? Is it the vacuum elements under the dash behind the center air outlets?

In defrost position though, warm air comes out from everywhere, although it's not extremely hot, as I would it expect to be.

Can you tell me what's wrong with it and - if it's under 50 degrees, and the aux. pump comes on - if the heating should work much better then? Because if that was the case, I would
be pretty happy, because there is no need of heating like crazy
when it's so hot outside anyway!

Thank you so much in advance,
I'm looking forward to hearing from you!
T.

stevebfl · #9 07-19-2002, 09:01 AM

If the servo is moving then the "system moves" or it should.

As one goes from hot to cold the center duct should shut-down and after the servo goes a little farther the heat appears. It may not even get to heat if the day is too hot. if the center vent doesn't close then its either not working properly or the system isn't "moving" far enough.

As to moving. Inside the servo is a clockwork mechanism,many gears working to drive the vacuum distribution valve (like a little maze on on side and all the vacuum holes on the other - as it rotates the holes are connected to different compartments in the maze), the electrical switchboard (drives the varying blower speeds cold - 5 hi down to zero then 4 hi - hot), and the the water valve allowing hot water flow. They are all geared together and they run a range that is all cold to all hot. Thisis driven by a small motor, as long as the calculation say go hot the motor is driven one direction. It stops when it thinks it has it right.

The decision to be evaluated is whether it "moved" the proper amount and whether things are chnging together (just because the servo links the vacuum doesn't mean it doesn't leak.

tschepplmasta · #10 07-20-2002, 05:55 PM

Steve,
thanks so much for all your advice! How can you know all that?
It's amazing!!!
By moving from cold to hot, the center vents ALMOST shut down - just a little air continues to flow. This little air becomes hot after
a while, but mostly on the passenger's side, as I said. I am wondering if this is the case because the aux water pump doesn't switch on because here in california it's never under 50 degrees...?
As soon as the dial is on max. heat mode, the blower motor
switches to it's lowest gear - maybe because it's just not cold
enough in the car? Would that be a possible explanation?
Is the system built in a way that it just blows lots of hot air into the car if it's REALLY cold? I hope it's like that, this could mean that my car is working OK then.
The whole heating/cooling system wasn't in use for years, so when I bought the car, I got a new servo and replaced all the vacuum lines that were leaking (lots of them!!). A/C and everything actually works great now, and if I know if the heating circuit also is supposed to behave like it does now, I would be very happy.
Thank you so much for all your time and expertise helping me!!!
Best regards, T.

stevebfl · #11 07-20-2002, 06:23 PM

OK, now that you are seeing how it works I'll tell you the trick. Shame it will go to the archives. I'm sure a bushel basket of systems are going to get screwed with as a result.

First thing, I think you are probably doing alright unless its a lot colder where you are. You probably won't get heat except in defrost with the temp higher than the temp wheel setting. Also shut-off the compressor if you wish more heat.

The whole point is that the magitude of the cooling or heating attempt (by the system) is a result of the combined temp sensor values as opposed to the setting you have given. AND, that is where the secret lies. If you take a flashlight and look very closely on the right side of the temp wheel there is a white toothed gear about the diameter of a nickel. It is the positioning adjustment for the temp wheel. If you want it colder run the degree wheel in the direction of cold and then take a tool and continue the gear in the same direction. Opposite for heat.

The proper tool I have used is a thick feeler gauge cut with a saw tooth pattern on the edge. Cut the teeth with a carbide wheel and try to match at least one or two to the distance of the gears spacing. To view this the temp wheel must be pushed to the side and nothing needs be disassembled. Get up close.

tschepplmasta · #12 07-20-2002, 09:53 PM

Steve--
what a cool trick you told me!
I tried what you recommended - it's really easy to move the little white gearwheel, since it's not very tightly attatched to the temp. dial!
I didn't take a driving test yet - do you think, that this should also fix the heating problem if I travel to real cold areas? Or do you think I will still have to heat in DEF position?
Thanks - I'm looking 4ward 2 hearing from you!
T.

Kyle Blackmore · #13 07-20-2002, 10:50 PM

I've been following this thread and am amazed also at Steve's knowledge of this system.I also have a type 2 acc system and was wondering about the 2 amp fuse that supplies an always hot power supply to the acc amp.Steve you mentioned that the aux pump should only come on when the ambient temp is about 50,my pump circulates briefly when I shutoff the system or if the system is left on and the key is turned on for glow plugs.I thought this was normal,the only function I don't have with mine is ac,but I've never looked into fixing it.
About the 2 amp fuse,I found (after 2 years) the fuse holder,empty,under the relay cover.I traced the circuit on the schematic and it is a secondary power lead for the amp.I've replaced the fuse and the only difference I've found is the aux pump will briefly cycle with the key off.I have the MB service CD but the testing procedure is a little daunting..

BTW the aux pump seems to work no matter the temp.Thank you in advance

.

tschepplmasta · #14 07-20-2002, 11:58 PM

Hey Kyle,
I was just wondering if you could tell me where again to look for the 2 amp fuse you were talking about? Where is this "relay cover" you are talking about?

Kyle Blackmore · #15 07-21-2002, 12:39 AM

Hi T,the cover is on the drivers side inner fender,top.There's a clip on the end of it and it comes off to reveal two relays,the fuse holder(inline) is just tucked inside the cover.The 2 amp fuse is an oddball size and I had to get it at the dealer($2.20Cdn),I'm kind of curious why someone (PO?)would remove it.Good luck.

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