PBU update 1987 300TD
 

I recently purchased a used PBU from a forum member. Has anyone switched there's with a new one? As you can see from the pictures the new one is different from the old one. I can not change the bottoms and that is where the 2 screws go that hold the unit in my car. Any help is much appreciated.

When I punch in the part number on the unit I bought (124 830 33 85), this is the picture that comes up. It looks like my new PBU is missing the upper section.

Chris

PBU
 

Your problem is not the different bottom but rather the missing front. The PBU that you bought is supposed to have a snap-on black plastic front to make it look like your bad PBU. The two angled plastic brackets with screw holes are, in this design (the one you bought), part of the front, not the bottom.

Out of curiosity, can you determine the manufacturer of your bad PBU and the one you just bought? They should be either Bosch or Kammerer. The Bosch logo looks like a circle with an "H" in the middle while Kammerer units may be labeled "MK."

Many PBUs with slight differences were made over the years that the W124 was in production. Both of the printed circuit boards in your pictures are slightly different from my spare PBU, which was the original in my '87 300D Turbo (W124, OM603). The one on the left in your pictures, which is (I think) the one you just bought, looks closer to mine than the other, and I think the red sticker says Bosch, doesn't it?

Anyway, you need to contact your seller and find out what happened to the front piece, 'cause you should have received it with your purchase. It had to have been deliberately removed and not easily, because all of the pushbuttons must first be pried off.

Jeremy

The front is being sent to me next week. I looked at it for a bit longer before I put it back in the car. Apparently the old ones do not come apart. The new (used) one is a Bosch, good eyes. I'm not sure about the old one, but it shuts off when there is a problem and I think I remember reading somewhere that, that is what the Bosch does. When I put the good one in I'll try and figure out who made the original one. It may not be original as my car was abused in an earlier life.

Thanks for the reply.

It is written (in the 1986 "Introduction into service" manual) that a Bosch PBU shuts down completely when there is an overload (example: frozen aux coolant pump) while the Kammerer shuts down only the affected circuit. I have no personal experience, just what the book says.

That must be where I read it.

The one on the left appears to be a junkyard pull, I recognize that paint-pen mark. Was it tested?

Pulling the buttons without breaking the retainer is nearly impossible, at least I haven't been successful (about a 50% failure rate). Best of luck with that. Also, the '87s had a service bulletin on failures of solder-joints in the Bosch unit.

It was tested in the members car. So I'll have a fun time getting the buttons off mine? Looks like I should have bought a complete unit, huh?

Quote:
Originally Posted by Bio300TDTdriver
Transfering buttons and bulbs is not a problem. (Or so I thought) How did you test the unit?

Chris

Members response: "It was in my car for 3 months."

The trick as I remember it, is to get the (white) inner part off without it cracking. If it cracks, the buttons will pop off (partially or entirely) when you select another button and the cracked one pops up. Be very careful, study the buttons well before starting.

This was a working pull from my car. I Used it 3 months, I thought the Faceplates came off all of them which was my mistake, most of my PBU's I've gotten from the local Pick n pull, I opted to put the original back in because I sort of liked the Celsius wheel, Anyways I hope the Faceplate will help..