Electrical: Alternator needs attention

[Jungle_Jim]

Hi all

Yesterday I had the indignity of having to call the RAC for the first time in over 20 years... the alternator was failing. [1992 240 B200F]

The RAC guy sprayed in some contact cleaner, gave the alternator a bit of a tap, and it began charging well, and the car was fine for the 200 miles of motorway to get home.

The only reason I can think of for this to happen now is that recently I changed the radiator hoses, and probably some coolant got into the alternator, which may have affected the brushes.

So - the question is - should I put new brushes in this alternator, or, is this time to get another one, given that it's of unknown age, and possibly the bearings might be near the end (I've had the car 16 years and never had an issue with the alternator). Or else - maybe it just got some coolant in it, which affected the brushes until some contact cleaner went through it and fixed it, and that's that?

Thanks
John

[Bob Meadows]

Coolant spills on electrics can play havoc:~
I would think that you have identified the problem, checking & changing the brushes is quite straight forward and worthwhile as will be be a thorough clean.
Bearings can go, but again they can be tested once the unit is free of the belts.

Do you have an alternator/ auto electrical repair shop nearby? they should be able to give a quick diagnoses for peace of mind.
I would think that the unit just needs a basic service.
Good Luck.
Bob.

[Jungle_Jim]

Thanks Bob

OK - would you recommend just replacing the brushes - looks like some Bosch ones are available for under £15, or, is it more the done-thing to buy the regulator unit with brushes already installed? It looks like around £50 for a Bosch regulator, and they go down to under £15 on Ebay for the whole unit but not sure what the brand is.

In other words - I wonder if there's a reasonable OEM regulator (or brushes) for a price somewhere between the Bosch and the cheapest.

I would be up for swapping just the brushes, though obviously the whole regulator unit with brushes already installed would be more of a simple job. I assume that the contact rings would clean up with a fine abrasive - and those are available new as well if not.

Thanks again
John

[Bob Meadows]

John:~
I would do a partial strip and then make a decision, the brushes may be ok and the unit may just need a clean due to the coolant leak.

Slightly different is at one time I spilt coolant on the main/dip unit at the side of the inner wing on a '88 240.
Purchased a second hand unit but once I looked at the original internals giving it a clean and a new solder joint (coolant effected it) all is fine after a couple of years.

Try the above initially you should be able to see any potential problems and a good clean should do it-- bearings generally have a long life and if they go then you will have a warning i.e. noisy/rumble rather than immediately failing.
My choice would be this approach before buying parts that my not need replacing.
Hope it helps.
Regards Bob.

These indicators are very useful to monitor alternator & battery conditions.
https://www.ebay.co.uk/itm/175767072...Bk9SR5qjrJipYg

[Jungle_Jim]

Hi all
Just to conclude this...

I bought a new regulator/brushes unit from Brookhouse - it was a HC-Cargo brand (made in China but the company is 'part of Bosch group' - the Brookhouse fella said they've had no trouble with them). It was under £20. Once the alternator is out, it's a 10 minute job. The old brushes were close to being worn out.

All good now - sitting on 14v+ when driving around.

To anyone who hasn't worked on an alternator (as I hadn't) or doesn't know a lot about electrics, I would stress how easy and doable this is, to save money on a new alternator.

Most of this job (if you haven't done it) is getting the alternator out, and cleaning it if it's covered in oil and crud. With the alternator on the bench, you can check the bearings for play or noise (the bearings in mine were ok). (Remember to disconnect battery before removing alternator).

You probably could replace the regulator/brushes with the alternator in-situ on a 240, I'm sure many do, but I needed to have it on the bench to be able to see it all properly. On a 700-900, access to the alternator is better, so perhaps it is easier to do this in-situ.

The regulator units usually come with new carbon brushes already installed (the brushes could be replaced individually on the existing regulator if you wanted to keep the original Bosch-brand unit). Anyhow it's two screws to get it out, then clean the slip-ring contacts with iso-alcohol and/or contact cleaner, then the new one goes in, lining up the brushes with the slip-rings and tighten the two screws. A squirt of WD-40 to give some initial lubrication. That's it.

Anyhow - I just thought I'd point out how easy this was, to avoid a costly trip to an auto-electrician.

Any further tips or advice about this, appreciated.

Thanks
John