W124 - Electrical gremilins

[ModMan]

W124 300TE Petrol

- Still can't get the rev counter to work Checked as much as I can before I start replacing stuff

- Heated front seats aren't working. The other day the passenger heated seat was lit up on both sides, but now it's off and won't come back on. They used to work

- At the same time that the heted seats stopped working, the central locking won't work anymore with the key or alarm, however if I manyally push the button down then everything locks, and when I pull the door handle to open the door, all doors unlock (With key in ignition only)

Help

Jay has nicely fixed my A/C and exhaust so it's just these few gremlins annoying me now.

 

[ModMan]

Well I've now got time to look at the car again.

Central locking worked for a couple of weeks but doesn't work again now. Any idea's where the relay is? There is one that I hear clicking under the bonnet when i turn the key either way and I opened it and it looks fine. Could it be the convenience module?

Also, heated seats. I've looked under the rear bench seat, passenger side, and there is only one unit, the convenience unit. So I am missing the heated seat unit. I checked under the front foot carpet and in the plastic trunking but nothing obvious. Can anyone help?

I'll try and attach 2 pics. One of some wires under the seat Both seats the same, and one photo of the convenience relay with nothing underneath.

Help

 

[ModMan]

Under passenger seat. This looks like a plug but it isn't plugged it anywhere. It's the same on the drivers side:

Convenience module with nothing else under it:

 

[ModMan]

Ok, good news, I found the heated seat relay and gave it a clean but the circuit board looks worn in places. So just ordered another one like this:

MERCEDES SEAT HEATING CONTROL UNIT A 000 820 62 26 | eBay

I found it in the passenger foot well. It had some double sided tape on the bottom so it doesn't look like it was the factory unit or factory location. Lets see if the replacement unit fixes it, might arrive on Saturday, we'll see.

Now, to work out the central locking and rev counter!

 

[V12]

Have you checked the fuses on the back of the rev counter?

 

[ModMan]

Fuses on the rev counter unit itself? I did have the instrument cluster pulled mostly out to check connections and I didn't see any fuses on it. Where should I be looking?

 

[V12]

Their holders look just like the bulbs, but sometimes red or blue instead. I think one is for illumination, one for rev counter and one for fuel tank. Been a few years, but I'm pretty sure that's how it went.

 

[ModMan]

Thanks, I just went out and had another look, pulled a couple out but they were bulbs. I shall have a proper look in the morning though as it's a great tip, thank you

 

[ModMan]

Damn, just went out to have another look, it was annoying me. I found the red fuse (The blue is just a bulb) and it's fine, tested with a voltmeter. Oh well, nice try