W123 230ce alternator light

[grober]

At that money the HELLA is probably an exchange reconditioned unit rather than a new one- nothing wrong with that, but the price may depend on return of the old unit

 

[Servicepoint]

I don't know if you have a circuit diagram simple enough to help visualise what might be wrong. Back in the days of a W123 charging systems were relatively simple and all much the same in principle. The most likely cause is a failure of the rotor to produce a magnetic field without which there will be no output from the stator.

From the diagram you can see that for current to flow through the rotor winding, it has to pass through the voltage regulator D+ to DF. Briefly shorting out D+ to DF will diagnose a faulty regulator if the alternator then produces output. Then current has to pass through the brushes so you need to make sure they are making contact with the slip rings on the rotor. Lastly it's possible for rotors to go open circuit which can be tested with an ohm meter. The resistance should normally be 2 or 3 ohms.

Less likely is a stator winding failure but if you can show there is current passing through the rotor then there is only the stator windings and diode pack to investigate as possible causes.


View attachment 136550

Thanks.
That’s getting beyond my capabilities unfortunately. The local alternator specialist said he will obviously test it beforehand but at that point I might feel committed to going down the repair route.
I have actually now found a couple of used Bosch ones on EBay at £130 and waiting on a response on whether they have been tested as working so that’s another option.

I’m now thinking if there is another issue at play as this all came about when the brake wear indicator illuminated and are related?

 

[Servicepoint]

At that money the HELLA is probably an exchange reconditioned unit rather than a new one- nothing wrong with that, but the price may depend on return of the old unit

No it’s definitely new and still in the box. No return needed.

 

[Ted]

Looking like the alternator, I’m afraid.
It would be worth just checking that there is power to the alternator - there will be one or two thick wires- probably red - check that one of them at least has power with a test light if possible.
There is also a thinner wire - blue iirc - that is just the warning light wire (also provides initial excitation via the warning light) but as you say the warning light works there is unlikely to be a problem there.
The warning light should go out with ignition on (engine not running!) and that wire/plug removed.

 

[Servicepoint]

Looking like the alternator, I’m afraid.
It would be worth just checking that there is power to the alternator - there will be one or two thick wires- probably red - check that one of them at least has power with a test light if possible.
There is also a thinner wire - blue iirc - that is just the warning light wire (also provides initial excitation via the warning light) but as you say the warning light works there is unlikely to be a problem there.
The warning light should go out with ignition on (engine not running!) and that wire/plug removed.

Thanks Ted, I’ll give that a go.

 

[Servicepoint]

Looking like the alternator, I’m afraid.
It would be worth just checking that there is power to the alternator - there will be one or two thick wires- probably red - check that one of them at least has power with a test light if possible.
There is also a thinner wire - blue iirc - that is just the warning light wire (also provides initial excitation via the warning light) but as you say the warning light works there is unlikely to be a problem there.
The warning light should go out with ignition on (engine not running!) and that wire/plug removed.

Tested the wires at the alternator and there is power power at the red wire.
My options now are
the new Hella at £95
A used Bosch at £119
Repair of my own at £??

 

[Ted]

Personally I would go with the Bosch. IME they are very reliable, it is period correct and you now have a spare regulator along with spares from the original.
If you have the equipment, it is simple to test the alternator components but then you have the car off the road while you source them.
You pays your money…

 

[optimusprime]

Servicepoint Can i ask how long have you owned the W123?

 

[Servicepoint]

Servicepoint Can i ask how long have you owned the W123?

About 4 years now.

 

[ray_hennig]

My options now are
the new Hella at £95
A used Bosch at £119
Repair of my own at £??

The Hella one seems worryingly cheap. But a used one may have issues; bearing, regulator?

If yours is the original, I'd be tempted by an overhaul by a VERY reputable operator. New bearing and regulator, etc. It may be worth Googling for a highly respected company that can rejuvinate yours.

I wish I'd done that but I needed the car on the road. Maybe I'll still get the original rebuilt.

Good hunting.

R

 

[Servicepoint]

The Hella one seems worryingly cheap. But a used one may have issues; bearing, regulator?

If yours is the original, I'd be tempted by an overhaul by a VERY reputable operator. New bearing and regulator, etc. It may be worth Googling for a highly respected company that can rejuvinate yours.

I wish I'd done that but I needed the car on the road. Maybe I'll still get the original rebuilt.

Good hunting.

R

The local place I know that does the repairs are excellent and I’ve known about them for about 30 years but they can’t give me a price.
The Hella alternator is definitely new, someone bought it and didn’t use it, still wrapped and boxed. The used Bosch one isn’t worth it, it’s probably the same age as my own and I could just be kicking the can down the road so to speak.

 

[optimusprime]

servicepoint Thanks i thought maybe that the car was a recent purchase .

 

[optimusprime]

Get this free workshop manual - Model 123 Maintenance Manual Index

 

[optimusprime]

And anpther interesting site Diesel Mercedes | Woods and Barclay Automotive | Roswell GA

 

[Servicepoint]

Get this free workshop manual - Model 123 Maintenance Manual Index

Oh I think I need that

 

[optimusprime]

Good, i like to know that it will be of use to you and everyone that needs it .

 

[Servicepoint]

Good, i like to know that it will be of use to you and everyone that needs it .

I don’t think it actually covers my engine type, 230ce M102 E23?
The US didn’t want the 4 cylinder petrol

 

[optimusprime]

So i think its in this one just engine info Mercedes Benz Service Manuals dont worry now and then they ask for donations you can if you want but as yet i never have

 

[Servicepoint]

So i think its in this one just engine info Mercedes Benz Service Manuals dont worry now and then they ask for donations you can if you want but as yet i never have

Thanks, that looks like the one. Excellent.

 

[optimusprime]

Another happy bunny thats good .