W124 230TE auto 1991 - battery drain/auto central locking foibles

adrianb

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W210 E320cdi Est. W124 E220Est, W124 230TE, W123 230TE (various) W123 200T.
My last thread start today, I promise.

Battery Drain
I've got a battery drain problem which I suspect is down to water shorting something - maybe the central locking vacuum pump, which (I've gathered from other threads here) is hidden somewhere under the luggage area, and is a known suspect. The battery has started to discharge overnight (and sooner sometimes). I've made sure everything is switched off, but still the battery is completely flat by morning. Sometimes, when I've connected up a good battery, I can hear a faint whining which (isn't me - yet) I guess it is the vacuum pump chundering away.

Vacuum pump/central locking/sun roof
The central locking is playing up: it only works sometimes when I pull the ignition key out of the ignition barrel, locking all the doors with me still in the car. But sometimes it doesn't do this. Sometimes, when I lock the drivers door with the key, I can a hear a faint whining - but the doors don't ever lock. Also sometimes, when I lock the drivers door or the tailgate with the key, the sun roof opens to the "tilt" position. I think that maybe this car has the "auto lock/open" feature, and it's just all going a bit awry. It hasn't yet closed the windows and sunroof when I lock the car, but maybe if the the vacuum pump motor is shorting in the water, drying that out will fix the issues and everything will be OK again. I'll let you know.
 
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adrianb

Senior Member
Joined
May 24, 2004
Messages
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Location
Nr Saffron Walden
Your Mercedes
W210 E320cdi Est. W124 E220Est, W124 230TE, W123 230TE (various) W123 200T.
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Having a brace of sprogs of various ages, schools and colleges, and official "work" as well, it's a bit difficult finding time when a) I don't have to use the car b) I don't have official work or a domestic job on c) the weather / visbility is good enough to work on the car.

I've been carrying around a charged up spare battery in case the car battery packs in during the day, but so far it has only died at night.

A dry spell yesterday afternoon, so I popped outside to look have another quick look over the fuses and obvious stuff with the multi-meter. I'd noticed the automatic arial had been playing up before it gave up the ghost entirely, and sure enough it was drawing plenty of current with ignition off, the motor very hot and probably fried. Disconnected the fuse (fuse "C") which the fuse box lid shows includes the auto antenna, and which also disables the central locking, tailgate closing mechanism interior lights etc. but then got interrupted, and the the rain set in again before I could check further.

Next morning battery dead again - assume the antenna is connected somehow. Sure enough antenna motor is still toasty. I disconnected the two power wires from the antenna (a Hirschmann 2040) and then had to leave off.

This morning, joy - battery in rude health. Car starts second try. Something else has changed as well. The idle speed, which has been a bit slow at around 500- 700 in neutral (by the rev counter), now seems a bit fast (around 1000 - 1200). Only had a short run this morning, so maybe the motor wasn't warmed up properly and cold start mode was still in operation, though water temp was up to normal.

Checking out the antenna, I came across one sound bit of advice that certainly applied to me:

"if your Hirschmann antenna fails to operate, you might consider COMPLETELY disconnecting it electrically until it is fixed. Why? Because chances are, the unit will produce an unwanted parasitic drain, killing your battery. "

I might try putting the fuse back in and seeing if the central locking plays ball now. Then checking the oil pressure guage and no heater probs, if the weather holds up.
 

television

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Ignoring the cold start for the minute,,you can buy a new hirshman antenna from CPC,, they cost about £34 and they have two models
 


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