W140 battery drain

[sixto]

How generic a topic is this?

Battery 1 = came with the car. I found the radio code and hooked up the antenna connector (the one for extending/retracting). I also used the remote window up feature everytime I left the car. Within a month the battery died.

Battery 2 = I removed the radio and disconnected the antenna. I noted a 3 amp drain whenever I hooked up the battery. Seemed high so I disconnected the battery whenever the car would be parked for more than 4 hours. I mean I disconnected the battery right after shutting off the engine. After a couple of months, the battery remained disconnected for 3 months while the engine underwent a rod-ectomy. I hooked up the battery and ran it down bleeding the IP. I got the engine running with another battery then reverted to battery 2. Didn't use the remote windows up feature. Battery 2 lasted a couple of weeks, with the same disconnection regimen, then died. Shop test showed a dead cell, if I understood what they were telling me, and got a new replacement with no pro-rated charge.

Battery 3 = Radio and antenna still out of the loop, now disconnected the radio amp. I didn't disconnect the battery when the car was parked. Used the remote windows up feature once or twice. After a month, battery died.

By died I mean the battery doesn't have enough juice to turn the starter. Starts easily with a jump.

The charge light comes on while glowing and goes out quickly and stays out when the engine fires. Does this indicate that the alternator is fine?

Regarding the 3 amp drain, it's possible my DVM is bad or I'm not using it properly. Still looking for an affordable clamp type DVM to make this diagnosis easier/foolproof.

Any thoughts on what I should do next?

Thanks,
Sixto
93 300SD 3.0

[Parrot of Doom]

I can't see what your car could possibly do to damage the battery other than short circuit it - and then wires would start melting.

You need to find that 3 amp drain. I imagine that will make the issue go away.

[RKreutzer]

Hi there,
without DVM, no can do.
You need to disconnect the negative bat. cable and put the DVM between cable and bat. terminal. It should show the drain. Then disconnect the various circuits one at a time by taking out the fuses until you find the circuit that drains, i.e. you found it when the drain stops.
There is probably a longer and more detailed write-up in the archives.
You also need the DVM to see whether the charging is ok. With engine running, voltage on my Mazda is above 14 V, yet over time my bat. looses the charge.
I figure I don't drive it enough and now just connect a charger for a few hours whenever I feel the starter not turning strongly anymore.
Hope this helps
Reinhard

[CSchmidt]

Sixto,

That will drain most batteries over a night or a day. Drains then recharges I believe used to weaken the old lead plate batteries. That can cause a plate to fall over and short.

I agree you need a voltmeter / ammeter. Running, you should have 13.5-14.5 volts. If not your charging system isn't going to keep up.

To find the drain you are down to troubleshooting by process of elimination. Hook the ammeter in series with one of your battery cables and keep disconnection fuses until the drain goes away. That is likely the circuit.

The other hassle could be the drain comes from a short caused by some previous event. Like maybe some of that environmentally friendly wiring in the engine compartment.

Years ago a friend had a 74 Chrysler New Yorker. The Chrysler version of the 140. More wire than you can imagine. Each door had 2 lights, a lighter, power windows and locks. He had a short we couldn't find. We tore that thing apart. It turned out it had been in an accident and dash was removed. When they put it back in a wire was rubbing over a metal support bracket. Over time the insulation wore off and the short started. Hope your find is much easier.

Chuck

[sixto]

Hopefully the other shoe has dropped. Driving the SD this afternoon the SRS light came on then the charge light came on then the seatbelt light flashed then the clock stopped... had power steering and temp gauge was at 82*C so I knew it wasn't the belt.

Hopefully it was all caused by an incapable alternator. You know you have a 140 when you say that I'll take it off tomorrow and have it tested.

Now the question is - how does the charge light work? What's the threshold current for it to come on?

I'll also get a second opinion on the current draw. I isolated it to 5 fuses a few months ago. If I can verify my methods and DVM I can pursue it more confidently.

Thanks,
Sixto
93 300SD 3.0

[Peter Guenther]

If all the warning indicators flashed, starting with the seat belt, and the fuel, MPG, guages drop to zero, especially if you are using the wipers, and come back it is a marginal power supply in the cluster. It also cold be an indication of the alternator regulator or diodes, being weak. Do a search on "flashing indicators" the cluster can be repaired, or there was a fix to replace a capacitor.
http://mbcluster.com/

[sixto]

The gauges continued to operate. While limping home I expected EDS to cut out but idle speed held and the tach kept taching. I was wondering whether or not to trust the temp gauge but I presumed with power steering available the water pump was also turning.

I didn't think this newfangled alternator had a replaceable regulator and brushes but I'll give it a look since I see the part in FastLane. I'll crawl under a little later and see if I can remove the plastic cover.

Thanks,
Sixto
93 300SD 3.0

[cool]

is yours a 140 body with climate control? if so, check and make sure when you leave the car for less than 15 minutes and the REST lights are on, then thats your common culprit, it happens to majority of 140 production dating 1992 to 1995, solution, change climate control, no such repairable parts for that case, or you can send the unit to be repaired by Bergman.

[sixto]

That could be it. I don't know if REST works since there's no indicator light when I press it and the lights stay on in whatever mode it's in. I've pressed it once or twice to see what happens. I have no reason to use it though.

The ACC buttons are flaky. I can't get the passenger side to AUTO from bi-level. Have to go to deforst then select AUTO to restore AUTO. Passenger side up arrow doesn't work. Recirc doesn't work either. Gets hot or cold as neccessary which is good enough for now :/

Sixto
93 300SD 3.0

[cool]

Sixto where are you located>?

[cool]

I have extra control unit (not for sale) which you mihgt want to test with before deciding on purchasing one?

[Peter Guenther]

Cool is correct, it seems some vehicles produced between Jan and Apr 92 had a bad push button unit, it applied to vehicles with the charcoal filter. Kammerer were bad, Bosh were ok. As long as you are checking, is the circulating pump (REST) possibly running, the PSE also provides vacuum when the engine is not running. It is not on a switched circuit, and could be replenishing reseroirs for either the P+ side for lumbars or P- for vacuum I have fooled with it and it is possible to change flap positions with the ignition off I think. There seem to be a lot of leads but only one answer I guess

[sixto]

I'm in the SF Bay Area.

Sometimes the PSE pump will hum every few minutes while the car is running. The driver door lock is slow to unlock so maybe there's a leak. I've sat in the car for extended periods with the key out (and battery connected ) to listen for the pump. No hum. Who knows what happens overnight :/

Sixto
93 300SD 3.0

[tower]

From your past posts I'm surprised to see you having troubles. At your expense, it makes me feel good so see the experts have problems with the "s" series cars as at times I feel quite inadequate over what generally concludes in a simple solution. Best of luck figuring it out though.

[Jadavis]

Did you ever figure this one out?

I have a 95 S350 that is drawing 4.4 amps with the keys out. I checked all of the fuses and did not find the problem.

http://www.peachparts.com/shopforum/tech-help/247979-ground-non-fused-circuit-post2144629.html?posted=1#post2144629

-Jim