I’m having some issues with my parents’ 1989 300E. I’m basically the permanent driver for the car, so I’d like to fix it up a bit. If anyone has time, I could use some help with some electrical, vacuum, and mechanical issues.

Electrical
Fuse 9 and C appear to have shorts. Fuse 9 has a constant drain on the battery, and fuse C blows intermittently. My parents have paid several thousand dollars before to have them tracked down, and while several have been discovered in places like the rear dome light, the problem persists. Eventually they decided just to ignore it, so fuse 9 stays removed and a blown fuse sits in C.

Fuse 9 controls:
Fuse C controls:

In regards to fuse 9:
There is an after-market stereo in the car, and I’m fairly sure I’ve narrowed the short down to that. The radio works fine when the fuse is put in. However, I’m not sure what “diagnostic term. 6” and “relay comfort circuitry term. 86” are, so I can’t test those.

When using a multi-meter to take a reading, there’s a “clicking” sound. It happens only one time when the circuit is completed, but occurs every time without fail.

1. What are “diagnostic term. 6” and “relay comfort circuitry term. 86”?

2. If the radio short is just a bad wire, my parents should be able to help me fix that (they know how to splice wires). However, we're a bit fearful the issue is the wiring is just done incorrectly (wires spliced together that shouldn't touch). Is this a possibility despite the radio functioning with the fuse in?

2.b. If so, does anyone have any wiring guides so we can hook up the after-market radio correctly?

3. Any idea what the clicking sound could be?


In regards to fuse C:
I’m unsure of the cause. Sometimes the multi-meter shows current through it with the car off; other times it reads 0. As such, I’m not sure how to test this aside from unplugging things, putting in a new fuse, and waiting several days to see if it blows.

4. How should I go about looking for the short here?


Vacuum
The AC only comes out the side vents (rather weakly) and through the defroster. Reading from other people’s misfortunes here, I now know this to be an issue with the vacuum pods. I’ve already looked up how to replace them, but would like to confirm the part numbers to make sure the correct ones get ordered.

I found a list here, but those are for an ’87 300D. When we looked up the car then the part number, the numbers we found were:

I’m not sure which part is what though; all I know is that the footwell pod is not included in that list.

5. Which list of part numbers are correct? If the W0133-16… is accurate, what is the number for the footwell pod?

Assuming a replacement footwell pod can’t be found:
6. What does this direct airflow to?

7. Is there some sort of fix I can do on it?


Mechanical
These are mostly vanity, but if I’m already doing lots of work on the car, I figured why not.

The rear passenger door appears to be damaged. The issue seems to stem from the door stop brace. I’m not sure what the actual problem is aside from the door becoming hard to close. My parents are afraid of it getting stuck (to the point we don’t use that door at all).

7. How do I determine what is actually wrong with the door brace?


The cruise control doesn’t work. I’m not sure what the problem is. It seems like the stick is broken. If it were a compass, the stick would always sit in the “south” spot instead of the middle like I would expect. I can move the stick up and forward/back (after moving it up slightly), but it always returns to that “south” position. Nothing happens when moving the cruise control stick around.

8. Is there a guide to removing the cruise control stick and repairing it? I found something on removing part of the wheel and cruise control to fix the turn signal here which I can use to start with, but if there’s a guide about my issue I’d rather use that.


This problem isn’t actually a vanity thing.
We had the transmission fluid changed a few years back, and in the old fluid some metal shavings were found. We were told this means the transmission could die on us at some point, but haven’t had any other problems with the transmission thus far.

9. Anyone else have this problem in the past? Is the transmission likely to die on us?



-Hope Remains