Not Charging... - PeachParts Mercedes-Benz Forum

Graplr · #1 07-15-2009, 05:18 PM

My 126 is not charging. I changed the alternator and it worked right away, but then it was right back to the same thing. I'm stumped.

Here is what I've done/noticed-
(I have a remote door entry remote that lets me know the voltage of the car/battery at all times)

January- New battery
In February- added a Webasto for cold starts. Noticed stock alternator would not charge battery fully after running the Webasto for a full cycle if I took a short trip. Decided to buy a high amp alternator. Put it on and problem solved.

In May- noticed the battery was dying. Took the 'new' alternator off and the old one back on and all was fine. I tested the 'new' alternator at Autozone and it failed.

A week and a half ago on a drive I noticed my electronics started fading (and my volts were really low). I tinkered with the alternator and it would work while I pushed on the back of the plug, when I let go it wouldn't charge.

I noticed the plug on the alternator was sort of melted. I'm not sure if this was new or had happened a long time ago. I have all the wiring from the 116 I parted so I switched the plugs. No change.

I have an alternator from my 116 I parted. So I took the 116 one, along with the 'new' high amp one to Autozone. 116 tested good. So I swapped voltage regulators to see if that was the problem in the 'new' one. But both regulators worked in the 116 and the 'new' one still failed.

So I get home today and swap voltage regulators into the one on my car. No change. So I change out alternators. I put the 116 on my car.

Right away I'm getting 13+V at idle. Great! I take it down the road and after a block I'm getting 14V. Then all of a sudden it drops again. Same thing as with the original alternator.

What is going on? I don't think it is the battery since I get WAY below 12V at freeway speeds (anywhere from 7-11V) and the battery is only 6 months old.

Help! I'm getting sick of charging my battery with a charger every time I turn my car off!

Thanks!
Ryan

Diesel911 · #2 07-15-2009, 05:39 PM

If your 126 has a not Charging Light on the Gauge Cluster you have not mentioned that the not Charging light is on.
If you have a not Charging Light does it go on when you fist turn the Ignition Key and go off after the Engine is running.
Have you verified the Voltages you have been getting with another meter besides the Remote lock meter?
In the pic below the to Red Wires and the Two large slots have Battery Voltage all of the time. The skinney Blue Wire (this wire goes to the Ignition Switch and the No Charging Light) should have no voltage with the key off but should have voltage with the Key on.

If you have a problem inside of your Ignition Switch it could be cutting off the Voltage to the Blue Wire.
In the same circuit a falty No Charging Light Bulb will cause no charging. A Bulb loos in the socket or with a loose Filiment could cause intermittant no charging. (I do not know enough to say if a LED type bulb would cause a charging problem.)
A bad or loose ground could also cause no or intermittant charging (clip one Jumper cable safely to the Alternator Housing and one to the negative Battery Terminal).

Oily or slipping drive belts could also cause no charging.

Graplr · #3 07-15-2009, 05:46 PM

Quote:

Originally Posted by Diesel911

If your 126 has a not Charging Light on the Gauge Cluster you have not mentioned that the not Charging light is on.
If you have a not Charging Light does it go on when you fist turn the Ignition Key and go off after the Engine is running.
Have you verified the Voltages you have been getting with another meter besides the Remote lock meter?

Thanks for the reply.

The light on the dash is flickering (although you can barely see it during the daytime. And I hardly drive it at night since it is the middle of July and the days are really long.

I have used a mulitmeter (but not today). The battery drains so I know the remote is at least working right (it may not be 100% accurate but it lets me know the status).

Jeremy5848 · #4 07-15-2009, 06:04 PM

(1) Does the battery stay charged overnight or does the problem occur primarily when the car is running?

(2) Make sure the wires to the alternator plug are making good contact with the pins in the plug (should be soldered).

(3) Make sure the battery cables, connectors, engine to chassis ground, etc. are all good.

(4) Make sure the pre-glow relay is turning off. You can experiment by starting the engine, removing the 80A strip fuse, and then driving the car while watching the voltmeter. Stuck-on glow plugs can ruin a battery and charging system.

Jeremy

carnut · #5 07-15-2009, 07:22 PM

A flickering dash light is probably a faulty connection to the alternator or a failed diode within the alternator. I presume the belt spinning the alt. is tight, no pulley slippage from the alternator. The ideal test would be a LOAD test. A load test shows max amperage coming from the alternator in relation to the alternators rating. Also a load test would verify belt tightness, if loose, once under load, the belt would slip. If the alternator is rated at, say, 60 amps, then under load it should show virtually 60 amps. As you know an alternator will reduce voltage output as well as amperage output as the battery gets to a full charge, so a reduced reading is not abnormal. I think your primary problem lies with the wiring to the alternator. Was the replacement of the plug done by soldering in the connector? if not, I recommend it be done.

Graplr · #6 07-15-2009, 07:29 PM

Thanks for the suggestions. I've done most of them.

Here is what I've done-
1-Started car. Removed GP fuse. No change.
2-Put cables on alternator. Other end on negative battery terminal. No change.
3-Check voltage with multimeter. Same readings as remote.
4-Checked voltage on plug that goes to alternator with car off. Results were as should be. Two large plugs had battery voltage, while small one (blue wire) had none.
5-Check light bulb on dash. Filament appeared in tact.

One thing I thought of. My brights dash indicator light is not working. The bulb appears fine. The fuse is fine. Then I noticed I have a loose rheostat. I tightened it. But the results are still the same.

Anything else you guys can think of?

Shouldn't I be getting high voltage with the car running even if the battery is bad?

Thanks.
Ryan

Graplr · #7 07-15-2009, 07:35 PM

Quote:

Originally Posted by carnut

A flickering dash light is probably a faulty connection to the alternator or a failed diode within the alternator. I presume the belt spinning the alt. is tight, no pulley slippage from the alternator. The ideal test would be a LOAD test. A load test shows max amperage coming from the alternator in relation to the alternators rating. Also a load test would verify belt tightness, if loose, once under load, the belt would slip. If the alternator is rated at, say, 60 amps, then under load it should show virtually 60 amps. As you know an alternator will reduce voltage output as well as amperage output as the battery gets to a full charge, so a reduced reading is not abnormal. I think your primary problem lies with the wiring to the alternator. Was the replacement of the plug done by soldering in the connector? if not, I recommend it be done.

I forgot to mention I checked the belts. The alternator was spinning every time I looked at it when I checked the voltage output.

How would one perform a load test? How is it different than the test Autozone performed?

No, I did not solder the wires. They are crimped and heat shrinked. But I get full battery voltage on the plug side of the connection, so I assume voltage is passing though it.

Jeremy5848 · #8 07-15-2009, 07:52 PM

A mechanic to whom I mentioned this problem commented that he had a similar "phantom load" problem that turned out to be a stuck-on power window motor. The motor would draw current until it overloaded and the thermal circuit breaker would trip. The electrical system then appeared OK until the circuit breaker automatically reset. Then the problem would reappear again.

You need to determine whether your problem is coming from the charging system not producing enough current or whether there is some phantom load that is sucking it all away. I suggest as a next experiment, with the engine idling, transmission in park, parking brake off (chock the wheels if necessary), and engine hood up. Make sure all loads are off (a/c, radio, lights, etc.). Doors closed so the interior lights are out. A 1984 W126 diesel should be using almost no electricity in such a situation. [Leaving the parking brake off means the parking brake light in the instrument cluster will not be illuminated.]

With the ignition switch still on, use the STOP lever on the IP to kill the engine. The ALT light in the cluster should illuminate. Now disconnect the negative cable from the battery. You should get little or no sparking when you touch the cable to the battery negative post. More sparking means more load. If you have an ammeter, you may be able to measure the load. With everything off and the engine not running, it should be no more than an amp or two, possibly less (I apologize for not knowing more about the W126 electrical system). If you get significant sparking, something is drawing current. Start pulling fuses until it stops. The phantom load is in that circuit.

If you get little or no sparking, the problem is somewhere in the charging system.

Jeremy

Cr from Texas · #9 07-15-2009, 09:29 PM

Reading the entire thread, the problem started:

Quote:

Originally Posted by Graplr

In February- added a Webasto for cold starts.

I have no idea what a Webasto is but you don't need it in July. Have you tried disconnecting it?

Oldwolf · #10 07-15-2009, 09:34 PM

I think it is some type of an electric space heater.

http://www.webasto.us/am/en/am_rv_heaters.html

charmalu · #11 07-16-2009, 01:55 AM

It is an engine heater, heats the coolant. uses the vehicles fuel to run a burner to heat the coolant.

there are different models of them, some heat the engine as well as the passenger compartment.

Charlie

Graplr · #12 07-16-2009, 07:12 AM

Quote:

Originally Posted by Cr from Texas

Reading the entire thread, the problem started:

I have no idea what a Webasto is but you don't need it in July. Have you tried disconnecting it?

Of course you have no idea what this is...you live in Texas.
Try starting an old Mercedes diesel in -27F and then you tell me if you think you need one!

Graplr · #13 07-16-2009, 07:13 AM

Quote:

Originally Posted by Oldwolf

I think it is some type of an electric space heater.

http://www.webasto.us/am/en/am_rv_heaters.html

It is not electric, it is fossil fuel fired (mine runs off of gasoline). It does use a bit of electricity but the btus come from fuel. Mine is used to heat the engine (coolant), not space heat.

Diesel911 · #14 07-16-2009, 01:32 PM

Something electrical must ignite the fuel?

RichC · #15 07-16-2009, 02:40 PM

Something I halfway remember, that I have tried from a book.
-----

with the engine off and everything else turned off.

Disconnect the negative battery terminal.

Connect an amp guage between battery and disconnected terminal.

If the reading is high you have something that is using current.

Disconnect fuses one by one and see if the amp guage changes.

If it does your current drain is in that circuit.

If the guage is not effected by any fuses

the problem is likely in the charging system or
one of the unfused systems like the starter.