Fuse C - x30

[Green_E420]

Hello Everybody,

I am hoping someone can give me the right area to look for. Recently, I have been trying hard to get my e420 back to normal since I purchased it almost a year ago. I am having an issue with a relay clicking behind the fuse box on my e420 w124 with the car off.

I replaced the relay and it continues to click. However I also noticed Fuse C would blow sometimes but not always. Also my main dome light is not working on drivers door only, and the light underneath the door panel is out only for drivers side.

What I did come down to was at the x30 plug there are 4 harness’s. When I unplug two out of the four harness’s the relay clicking stops. This leads to my power antenna and door locks to stop working, and my dome light comes on and stays on.

I am not an electric engineer but kind of do know how basic electric works. I am thinking there is a short somewhere that I am obviously working on.

what is the best way to approach this before I rip out the interior. These two harness lead somewhere underneath the drivers carpet.

I checked between drivers door and chassis and wiring looks fine there.

TIA

 

[Green_E420]

Update,

Did some more digging.

There are four harness’s on the x30 (under dummy pedal).

I traced and confirmed.

First Harness powers the Rear Roof Light, Trunk Light, Door Lights, Aut. Antenna. Uses Pin 1,3,5.

Second Harness powers the Power Door Locks. Uses Pin 1,2,3,5.

Third Harness (labeled 124-440-13-09 EDW Cable (Alarm) Without this plugged in car won’t start. Uses Pin 1

Fourth Harness = Pin only in 3,4,5 ( rear headrest)

The relay ticking stops when first and second harness are unplugged together only.

Fuse C is labeled rear roof light, trunk light, central locking system, door lights, reading lamps, aut. antenna.

As far as reading lamps, is this the same as dome light?

talk about gremlin…. Any help would be appreciated.

 

[speedy300dturbo]

Dome light and door puddle light not working with driver's door open (but OK with passenger's door) is a classic symptom of a fried or shorted out seatbelt warning relay (behind the instrument cluster).

 

[Green_E420]

Makes sense now, with the door symptom. My buzzer hasn’t been working.

Still need to know what the issue is with the short.

 

[Green_E420]

seatbelt relay wasn’t plugged in all the way, this is now good.

However I’m still having this clicking sound on the relay.

also noticed alarm light bulb does not come on the dash, with the doors locked

 

[Green_E420]

any one have any ideas?

today the alarm started to work after I lock the doors with the keys and opened from the window but antenna stopped working…

. An hour later I park the car … the alarm stops working but antenna works fine

 

[gsxr]

can you provide a list of the current symptoms / problems? How do you know if the alarm is or isn't working? I've bypassed the alarm on a couple of my cars as it's more of a nuisance than anything.

 

[Green_E420]

For a whole week I Turn off car, lock the doors … alarm light does not blink …. When I turn on the car the power Antenna works and door locks work….. also if the car is parked and I try to unlock door through the open window without a key the alarm does not go off obviously because it’s not activated

Today I got in it, power antenna did not work, door locks worked fine, when I turned off the car I locked the doors and alarm light blinked…. I unlocked it from the open window and the alarm goes off….

Also no matter what the relay is clicking non stop with the car off ….in the fuse box all the way in the back….

 

[gsxr]

You might have separate issues that are happening at the same time by coincidence, with the alarm and power antenna.

However, the relay clicking nonstop with the ignition off is NOT normal. I'd start by chasing that down first. Use the factory manual electrical schematics to determine which relay is clicking and what it controls:

24 Electrical Troubleshooting

 

[Green_E420]

You’re awesome! Thank u for this.

The imobilizer gets its power from Fuse C as well it’s also tied into the x30.

 

[Green_E420]

The relay that is clicking is F. Which is comfort control module. Most likely this unit might need to be checked out.

 

[Green_E420]

Did some troubleshooting on the Comfort Control Module. Are the windows suppose to go down as well? Mine only go up when I use the key.

 

[gsxr]

The convenience (comfort?) module, under the rear seat, should roll all windows up when the key is held in the lock position. And when unlocking (when all windows are up), it should roll all of them down. This should be documented in the owners' manual.

 

[Green_E420]

Interesting, maybe a short in the convenience module. I forgot what it was called as for Mercedes. My dads 87’ did not have this. I’ll check it out. Thanks!!

 

[gerryvz]

The convenience module was phased in around 1990 or 1991, if I remember correctly, on the W124.

 

[gsxr]

The convenience module was phased in around 1990 or 1991, if I remember correctly, on the W124.

Yes, it was part of the 1990 facelift / MOPF1.

The owner's manual only says the system closes the windows, not opens them... I need to check on that.

 

[Green_E420]

So Today I went ahead and removed the rear seats and accessed the convivence module. Part #202 820 09 26. With the doors locked, I still hear the relay clicking, once I unplug harness E on the module the clicking stops, however I can't open my windows after but door locks still continue to work fine.

Since I went to one of those pick and pull junk yards in Pennsylvania a year ago, there was a white w124 that I bought some modules including the convenience.

I swapped out the module and so far the clicking has stopped. Hopefully this has solved my issue.

Things I noticed about the original module in the car, there looks to be some type of sticker in the upper right hand corner (k5 of ks) some type of code or initials, and some white residue on the back of the module when removed. The car I'm working on has ridiculous low miles, not sure if maybe some type of condensation got on it from maybe sitting at one point. I had already replaced the wiper module due to the speeds not working correctly not to long ago.

Finally now the alarm actually sets it self correctly. I can see with the doors locked and peaking through the window the red light is blinking. This means my alarm is now working again. However, I tried opening the door through the window and the horn and lights go off for 2 or 3 times then cuts off. Not that its a big deal for me to fix, I can live without it since GSXR said its a Nuisance. Is the alarm horn separate by any chance? and also does unplugging the alarm under the passenger floor give any other issues? The model year is 1994 and there is a immobilizer, im sure there is someway to bypass it if I search somewhere here.

I really appreciate all the help on here, you guys rock!

Pictures

 

[gsxr]

Sounds like good progress. Yes, the alarm horn is separate, near the ABS (or ASR) unit behind the driver headlight, you can disconnect or remove it. The immobiliser (which just cuts the starter) can be bypassed if you disconnect the alarm system at the control module in the passenger footwell.