W123 230ce alternator light

[Servicepoint]

My car has been garaged up for the winter and only periodically started over the last few months.
I noticed today when I started the car that the battery warning light was on. The car starts first time and the alternator belt is in place and not slipping. Some might remember I did have an issue with the belt slipping and was advised on here how to adjust. A couple of things now spring to mind, have I tightened the belt too much and destroyed the alternator ( I can’t turn the belt by hand) or has the alternator just failed?
I have the battery on charge at present to see whether this helps.

Not sure if this is related but the previous time of starting the car the brake wear indicator was illuminated on the dash, the pads are definitely not worn as I had the callipers off for refurbishing and the pads were as new , I assumed it was the wear indicator leads that were the issue as these are still original and I believe prone to failure? The two warning lights are side by side on the left of the binnacle.

Any advice would be appreciated.

 

[Ted]

I would check to see if it is charging first, then if not, replace the voltage regulator - an easy and cheap(ish) job on a w123 and the most likely cause of a charge warning light.
It’s a small black box on the back of the alternator held in by two screws. As a bonus it also has new brushes.
Disconnect the battery negative as a precaution when you do it.

 

[Servicepoint]

Thanks Ted.
I noticed the voltage regulator on the alternator but wasn’t sure how to remove it.

Had a quick look online for a Bosch regulator, I’m assuming it would need to be a Bosch one as it’s a Bosch alternator? All seem out of stock.

 

[alabbasi]

Did you rev it? Sometimes it takes a few rpms to excite an alternator

 

[Ted]

The original was bosch and that’s what I would fit but there are (were) pattern ones that would fit

 

[Servicepoint]

Yes, I tried reving it to see if that put the light out but didn’t make a difference.
Crazy price for the Bosch alternator, £465, if they were on stock anywhere.

 

[zipdip]

Have you checked that the battery is being charged or not,that would be what I would do first,if not make sure any connection on the alternator are tight,as you can see the regulator,maybe look on Ebay seem to be a number on there that say will fit a W123

 

[Servicepoint]

Have you checked that the battery is being charged or not,that would be what I would do first,if not make sure any connection on the alternator are tight,as you can see the regulator,maybe look on Ebay seem to be a number on there that say will fit a W123

I’m going to check the battery is charging with a multi meter today. All the connections appear tight too.

 

[Servicepoint]

I’m unable to source a genuine Bosch replacement Regulator 1197311 009, all out of stock and nothing on EBay.
Can anyone recommend another make plenty of Beru, Ridex etc?

 

[optimusprime]

Regulator is faulty . Once you have a new reulator ,remove the battery leads .Remove both screws holding it in to the rear of the alternator and replace the regulator , And if you want, you can replace the brushes in the old one. I replaced the carbon brushes in mine . Just take the size from old carbon brush then buy a pair off Ebay the same ,,or even larger, they are easy to file down to size with glass paper .They are all the same length ..But it is important that the braid must come out of the new brush in the same place as the old ones,, the reason for this is, so the brade clears the spring that holds them in .Try Hitachi if hard to find a Bosch

 

[Servicepoint]

Regulator is faulty . Once you have a new reulator ,remove the battery leads .Remove both screws holding it in to the rear of the alternator and replace the regulator , And if you want, you can replace the brushes in the old one. I replaced the carbon brushes in mine . Just take the size from old carbon brush then buy a pair off Ebay the same ,,or even larger, they are easy to file down to size with glass paper .They are all the same length ..But it is important that the braid must come out of the new brush in the same place as the old ones,, the reason for this is, so the brade clears the spring that holds them in .Try Hitachi if hard to find a Bosch

Great thank you.
I think I’ll just go with a new regulator, I’ll take the original out and check the size as I see there are two different plate sizes.

 

[grober]

CHECK YOUR ENGINE EARTH STRAP AND ITS CONNECTIONS FOR BREAKS /CORROSION

 

[Servicepoint]

Tested the alternator/ battery and it’s not getting a charge, 12.8v off and 12.4 when engine is running. I’ve taken off the VR and going to order a replacement.
Fingers crossed.

Appreciate all the help and advice.
Thanks all.

 

[Ted]

It does sound like the voltage reg then. Those alternators are pretty reliable - the reg less so. Definitely worth a change rather than the cost of an alternator

 

[Servicepoint]

Update

Fitted the new Voltage Regulator today and tested and unfortunately it’s not cured the issue. Battery light still on and when I tested with the meter I’m not getting the correct readings. I also noticed the alternator was pretty hot to touch after a short period of running.
I’ll probably need to look at an alternator repair or replacement now.

 

[ray_hennig]

I’ll probably need to look at an alternator repair or replacement now.

I got a restored Bosch alternator for my 124 a couple of years ago for 2 or 3 hundred quid. All well so far and much cheqper than MB.

Get the MB part number and then search AutoDoc. Bosch may be available there. AutoDoc's in Berlin, I think.
RayH

 

[Servicepoint]

I got a restored Bosch alternator for my 124 a couple of years ago for 2 or 3 hundred quid. All well so far and much cheqper than MB.

Get the MB part number and then search AutoDoc. Bosch may be available there. AutoDoc's in Berlin, I think.
RayH

I searched Autodoc for it but it’s showing out of stock for the Bosch part no (£450 if it’s in stock). They do have a Hella for £137 that is a match. I also have a local place that does alternator repairs but they can’t quote a price until they know what’s involved. Not sure whether to go with the new Hella or a repair.
Actually can get the Hella for £95

 

[zipdip]

Well depends if you want to keep the original alternator,you are lucky you have a place local that does repairs,the Hella one is cheap at £95 it's decision time

 

[Servicepoint]

12.3 engine off
12.18 when engine running
11.7 with load

From these readings I assume it’s a bad alternator.

 

[190]

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.