Altenator plug - Page 3 - PeachParts Mercedes-Benz Forum

LUVMBDiesels · #31 11-27-2007, 03:18 PM

Quote:

Originally Posted by Masterful1

ok so I checked the bulb all seems well there, so I guess its pull it and take it to my local rebuild shop so they can have a look at the alt.

did you get the bulb to light up? try it in another socket. I still think that that circuit is the problem...

Try tracing it back from the bulb to the thin wire on the alt plug.

LUVMBDiesels · #32 11-27-2007, 03:25 PM

Quote:

Originally Posted by chetwesley

Hmmm... so are you saying a faulty battery light can cause the alternator to not do it's job?...

YES YES YES!!

That is the circuit that excites the alternator. if the light is burned out or if it is not working you will not get anything out of the alt.

To check voltages, you can get the car started, then disconnect the negative and positive leads from the battery. If you get 13+V from the leads, the alternator is working. If the car is a gasser and it is still running the alt is working too

You can also check the voltage at the black junction box (on the right fender on W126 cars) I would almost guess that either the thin wire is bad at the box or you have corrosion in the box...

Oh dumb question, but you did clean up all the corrosion on the battery terminals and everywhere else you found some, right?

chetwesley · #33 11-27-2007, 04:41 PM

Quote:

Originally Posted by LUVMBDiesels

YES YES YES!!

That is the circuit that excites the alternator. if the light is burned out or if it is not working you will not get anything out of the alt.

To check voltages, you can get the car started, then disconnect the negative and positive leads from the battery. If you get 13+V from the leads, the alternator is working. If the car is a gasser and it is still running the alt is working too

You can also check the voltage at the black junction box (on the right fender on W126 cars) I would almost guess that either the thin wire is bad at the box or you have corrosion in the box...

Oh dumb question, but you did clean up all the corrosion on the battery terminals and everywhere else you found some, right?

My junction box has 25 years of dirt and dead spiders on it. I can try unscrewing the terminals and cleaning them off. There is supposed to be four connections at the terminals, right?

My battery is new and the connectors themselves are good and clean.

The alt appears not to be getting voltage to the battery, as there is no rise in voltage when the car is running from when it is off (actually, a slight dip in voltage when it is running, and even more when you turn on the lights, etc)

SD Blue · #34 11-27-2007, 06:46 PM

Quote:

Originally Posted by ichbineinekrous

I have a hypothetical for you. IF someone were to forget to disconnect the main battery leads before installing the new voltage regulator causing sparking at the alternator housing during said installation, AND IF the new regulator didn't want to go in at one point during install and after taking it back out the brushes were pushed out of their respective places and kind of hanging by the little springs, HYPOTHETICALLY is all I'm sayin'. Could something have gotten fubar'd? Before I was getting 42 amps and 1.5 volts and after this little debacle, no amps or volts. I mean, not me personally, but I mean, damn never mind,

it was me.

It is hard to say what kind of damage may have been done but you may have only damaged the voltage regulator....requiring a new one. It's kind of a gamble as to whether this took out the rectifying diodes also. The gamble is...$20 for a regulator, which may not fix it or an additional $120 for a replacement alternator. Personally, I would take it to an alternator shop and let them deal with it after this type of scenario.

Masterful1 · #35 11-27-2007, 08:06 PM

Quote:

Originally Posted by chetwesley

Hmmm... so are you saying a faulty battery light can cause the alternator to not do it's job?

yes I am saying that a burnt out bulb could possibly cause the alternator not to work

Uncle Possum · #36 11-27-2007, 09:45 PM

I fought this problem this summer, ended up replacing my alternator twice (the first replacement alternator was bad). Anyway, one thing I found out is that if the check battery bulb is burnt out, then the alternator will not charge. The bulb is in the circuit that supplies the field voltage to the alternator, no field voltage = no charge. I also read a post somewhere that the brake pad light is in the same circuit, but I can't verify that.

To check to see if the bulb works, follow the alternator plug back to the terminal strip. The field wire will be the blue one (at least on my 82SD). Run a jumper wire from the field wire to the (+) terminal on the battery. Check to see if the battery light on the dash lights up. If it does, then most likely there is something wrong with your alternator.

Good luck!

ichbineinekrous · #37 11-28-2007, 09:34 AM

Quote:

Originally Posted by SD Blue

It is hard to say what kind of damage may have been done but you may have only damaged the voltage regulator....requiring a new one. It's kind of a gamble as to whether this took out the rectifying diodes also. The gamble is...$20 for a regulator, which may not fix it or an additional $120 for a replacement alternator. Personally, I would take it to an alternator shop and let them deal with it after this type of scenario.

So I can't visually see if damage occured? By looking into the alternator through the VR hole? Also where does one find a voltage regulator for $20, I was out of town when this occured and got hit for $73 by the mercedes dealership in Lancaster, PA. Should've just bought the $100 remanned beck-arnley alternator from the local import parts place.

LUVMBDiesels · #38 11-28-2007, 09:40 AM

I was running up the highway when my RADAR detector started blinking "Low Voltage" At the same time the headlights started dimming. I got off the road and checked things out. It turned out that the wire from the alternator to the battery wire had come loose

Not only did this prevent the alternator from operating, it meant that the dashboard light did not come on!

I popped the wire back on but had drained the battery enough to require a jump start. Once the car was running I had to goose it up to 1200 RPM one time before the alternator would excite and start charging.

This proves that that circuit is a major potential failure point in the charging system. It also proves that these cars really NEED a volt meter...

chetwesley · #39 11-28-2007, 11:02 AM

Quote:

Originally Posted by ichbineinekrous

So I can't visually see if damage occured? By looking into the alternator through the VR hole? Also where does one find a voltage regulator for $20, I was out of town when this occured and got hit for $73 by the mercedes dealership in Lancaster, PA. Should've just bought the $100 remanned beck-arnley alternator from the local import parts place.

Yikes! The local car electronics rebuild shop quoted me $13!

SD Blue · #40 11-28-2007, 11:33 AM

Quote:

Originally Posted by ichbineinekrous

So I can't visually see if damage occured? By looking into the alternator through the VR hole? Also where does one find a voltage regulator for $20, I was out of town when this occured and got hit for $73 by the mercedes dealership in Lancaster, PA. Should've just bought the $100 remanned beck-arnley alternator from the local import parts place.

Try here for about $30: http://catalog.peachparts.com/;)

PanzerSD · #41 11-28-2007, 04:04 PM

I pay $7 for a voltage regulator...NAPA

ichbineinekrous · #42 11-28-2007, 05:33 PM

Quote:

Originally Posted by PanzerSD

I pay $7 for a voltage regulator...NAPA

wow how about that canadian dollar! I just looked online and NAPA wants $84.89 for the bosch part and $54.89 for the Beru. This is voltage regulator bosch part # 1197311021

Masterful1 · #43 12-03-2007, 06:29 AM

ok to sum this thread up and maybe give someone else an immediate answer to their charging problems, here is my trouble shoot on the charging system now that I know it like the back of my hand.

scenario 1:
Dead battery, no prior warning via dash lights, and all the dash lights come on when you switch the key on (once you recharge/jump your battery of course).

1. test battery, easily done at local parts stores for free.
2. test alternator, can be done several ways, easiest IMHO is with voltmeter across battery terminals (reading 13+ at idle means your charging)
3. check the terminal box on the right fender where the alternator leads meet battery leads for corrosion, and general dirt.

this one is most likely the battery.

scenario 2:
Dead battery, warning light has been glowing at idle but goes out at higher RPM, dash lights all come on when you switch the key on.

check the things in scenario 1, but odds are its your voltage regulator going bad.

scenario 3:
Dead battery, no warning lights, only glow plug light comes on when you switch key to start.

check things in scenario 1
also pull your cluster out and check the bulb for the battery light, brake indicator light. plug them in to a light you know you can get to light IE high beam indicator light and test them.
also check the small wire on the alternator plug for continuity to these bulbs.
if all that checks out you will probably need to replace your alternator.

mine was scenario 3 and I checked everything there was to check without actually taking the alternator out and looking at it. I took it to a local alternator rebuilder, good guy have taken a few things to him... he took it apart and gave me the lowdown of what was going on with it. he told me he could rebuild it but it would cost as much to do as just getting a new one, and he said the new one would be more reliable, due to the amount of wear on the housing. I got a new one and put it in, no more charging troubles, yet.

also as a side note if you are ever traveling through mid-Missouri on I-44 and have alt/starter problems I highly recommend Harold in Cuba, he's honest and fast, has been doing it for almost 30 years now. I also like that he will bring the part out to you and point out what exactly has went south in it before he replaces it. I once took a starter to him which he rebuilt in about 30 mins, and he only charged me $20. starter still works just fine over 6 years later.