W140 93 300SD convenience module problem
 

I've been using a lot the feature that closes the windows and sunroof using the key. Usually from the driver side. I used it once on the passenger side. A few days later the battery was flat. I get a 3.25 amp draw when trunk fuse 5, 6, 11, 15 or 16 are in place. I believe all those systems (windows, anti-theft, stereo) hook into the convenience module.

I disconnected the module (those connectors are a proper Chinese puzzle!) but still the draw. I checked continuity to ground of pin 9 from the door lock switches and got ~150 ohms. Not sure if that's open or grounded.

The closing assist pump is off the car for service.

Am I on the right path thinking the draw has to do with the convenience module? Any thoughts on what I should do next?

What is IRCL?

Thanks,
Sixto
93 300SD

Ircl =
 

Infrared Remote Central Locking

Afraid I have no other input of value.

Regards

It can be very frustrating doing the resting current draw test on the newer MB's, and the 140's were especially problematic. Need to lower a window and lock the car, pop the trunk, simulate closing the trunk, then hook up the ammeter and wait about 5-10 minutes. Some of the newer cars you have to wait longer than that. These will have a bit higher resting draw than other cars, 30-40 ma not unusual. Whats the age of the battery?
Gilly

Don't know about the battery. Came with the car.

Current battery is a couple of days old.

Could be the battery just died.

Sixto
93 300SD

Well, except that if the resting current draw stays at 3.5a, that's way too high. That is about enough draw to be a small bulb.
Gilly

I can't quite figure that one out. I put an ammeter across the ground cable and terminal and keep the circuit while lifting the ground cable. I get the ~3.25 amps reading in the ammeter. Still keeping the circuit I replace the ground cable and the antenna motor whirs. I know it's the antenna motor because the trunk lining is off and the antenna is not too far from my ear. The central locking (PSE?) pump is a fuel tank and seat cushion away. It could be running but I can't hear it. The point is, I don't have complete faith in my ammeter. Why would the antenna motor sense reconnecting the battery if a circuit was maintained by the ammeter the whole time?

Physics is fine until you get to things you can't see like electricity and magnetism :)

Sixto
93 300SD

Dunno but I'd definitely pull the power connector off the antenna and retest. Antennas are known for causing power drains.
Gilly

Antenna was disconnected when I got the car, and hence when the battery went flat. I didn't reconnect it until I got the new battery and noticed the current draw. The motor hums but the mast doesn't move. The draw doesn't change whether or not the antenna is connected (the 4 pin connector).

Thanks,
Sixto
93 300SD

This striles me as being pretty weird if I am understanding what you are saying. You are saying the draw measures the same whether the antenna is plugged in (and humming) or not? If the antenna is humming it has to be drawing amps, and probably a pretty good amount of them too. Or do I have it wrong? UNLESS the humming is the antenna motor just spinning with no load (something broke inside) and not actually a "straining" type of hum. Kind of like the difference between just standing somewhere whistling, or a "grunting" noise because you're trying to lift something, if that makes any sense to you.
Gilly

No clue either. I don't know why the antenna won't run when power goes through the ammeter only.

Sixto
93 300SD