[Retromodo]

Hi all

Hope you’re all well, w123 200 m115 engine (petrol) manual.

Went for a drive and indicators stoped working lights dim. When I parked up battery light came on and it was dead. Battery was old so put in brand new one (voltage was over 12.6) started up straight away but then the battery light was on constantly.

I checked the voltage and when engine running was giving me over 13.7v, I changed the voltage regulator (from original Bosch 0192052008) to a hella replacement one. Once fitted started all ok but battery readout varies at 12.15v when the car is running even with heater on full and lights on. Battery light is still on in dash though.

So is it a case of dodgy voltage regulator or alternator? Should I check the earth? Also a little bit of oil leak from before and it’s been pretty cold wet in the uk.

Any ideas or steps to check?

Thanks

 

[Retromodo]

Welcome to you. Can I recommend putting your car model and year into your profile for us please? Complete your Profile

I don't think I'd trust any other VR than Bosch, personally.

apologies added details, ah I understand what you mean. I couldn’t find any, should I goto Mercedes directly? Anything else I could check to clarify if it is the regulator?

 

[Retromodo]

You did not state if the headlights or other consumers of electricity were on when you read the 13.7 volts. When testing anything make sure all variables are the same so that you can distinguish differences. If any electrical consumers were on during your first test I would say that 13.7 @ idle is good.

I get 14.2 @ idle... no consumers.
I get 13.6 - 13.8... depending on the number & type of consumables @ idle.

I have a Brand New Bosch Alternator.

Hi
Ah thanks both times no lights/heater etc was on.

will do some more tests and put back the results

thanks for the help

 

[Retromodo]

Ground Contacts: Clean where the Battery Cable meets the Fender, there is another from the Starter to the Bell Housing. I would also add a ground wire from the instrument cluster to the Fire Wall... this one is a big deal and probably does more to 'fix' instrument cluster issues than anything else. I'm speaking to mid 80(s) W123 Diesels yours may vary.
If I missed one guys... please chime in.

Okey dokey will have a clean of them, as due to a slight oil leak and bit of rust over the years

thanks

 

[Retromodo]

Why would someone only clean the grounds? Clean all of the battery connections.
I am assuming that the alternator on the gasser has the same alternator electrical connector.

Don't know how much room there is to do this on the gasser. When you remove the alternator electrical connector you will see that it can be taken apart.
I suspect what you are going to find is the are the wire connect to the brass connector and or the brass is corroded. Depending on what you find will determine your action.

While the electrical connector is out remove the voltage regulator and look inside at the metal sort of finger that makes contact with the voltage regulator if that is corroded it needs to be cleaned.

This is a pic a corroded contact finger
View attachment 2801419

Also look inside at the condition of the slip ring.

There is also a test using an electrical multi-meter (volt Ohm meter) that checks for AC current. One of the names for the test is a voltage ripple test.
What it is about is that you can appear to have good charging voltage but there is a diode issue that is putting out too much AC voltage.

Do a google image search and there are various videos on how to do it. Due to the type of plug-in electrical connector you limited to reading it over the 2 battery terminals. The main thing is you need to know what AC voltage to set the meter to.

There is also another test called the voltage bypass test that will tell you if your battery cables have too much resistance. Again, instructions on the internet buy doing a google image search.

I put in a different battery ground to chassis cable and found I got a whole other volt during charging afterwards

If your probe the disconnected alternator electrical connector with your voltmeter:
The 2 large slots on the alternator electrical connector should always have battery voltage. The single smaller slot should have no voltage when the key is off.
On the diesel when you turn the key on the voltage only drops about .3-.5 volts. I am not sure how much the voltage drops on a gasser due to the ignition and if it has an electric fuel pump.

Cool! Ok mate will get cracking with the suggestions, thanks so much. Appreciated, will update with results on these.

 

[Retromodo]

Ok
Due to time/weather etc could only do voltage test so far
12.4 before start
12.08 when running (even at high revs)
11.56 when lights hazards and heater on full
12.4 when I tuned the engine off

I cleaned the ground contacts and the inside of the alternator clip. I tried both voltage regulators (original Bosch) and the hella replacement results were the same.

Will do the other tests in the next day or so (subject to weather)

 

[Retromodo]

Keep at it!!!

If you have a trickle charger you may want to keep that new battery fresh while you are not working on the car as you are draining the battery... even @ idle. It will not be long before you will start getting 12.2 and then 12.1 etc 'before start' unless the battery gets some charge.

I hate to say it... but, I smell a 'new alternator' in the not to distant future.

Yeh I will do… ill keep an eye on it.
Thinking the same… down the route of a refurb or new one?

 

[Retromodo]

 

[Retromodo]

Rebuilds are fine... they are around 200 (including a core charge) so you will get 50 or 60 back ... so, 140 to 150 range (with free shipping).
Shop around and get it from someone reliable like Pelican, ECS Tuning etc. Don't trust eBay Sellers.

OH! Get the 65amp Rebuild! Double OH! Sorry, Yer a BRIT! Still don't get it off eBay!

Cool will do, most eBay ones available for uk are from Germany. But will have a hunt around while I’m waiting to do other tests.
Cheers mate

 

[Retromodo]

Thanks for the apologies for not being able to update weather here has prevented any. Will get on cleaning it, hopefully weather will be better tomorrow for it.

yep Bosch is the way to go, will do all of the above and update.

thanks everyone for the help and input

 

[Retromodo]

Cool mate, I checked the tension on the belt spot on 30 freezing here so only managed to do that will do the cleaning and diode/amp etc checks in next few days
Thanks everyone for the help

 

[Retromodo]

Hope everyone is well ok sun out in London still freezing but did something

cleaned the slip rings, re tightened double checked the voltage regulator, cleaned all the contacts.

voltage on battery was around 12.4 starting load it stayed around 12.2

(Voltage ripple test) was 0.01/0.02


with fan on full, hazards, lights full and beam voltage was around 11.4
(Voltage ripple test) 0.02/0.04

when engine turned off after battery voltage was back on 12.4

I can’t find the refurb Bosch alternator here in the Uk anywhere.

 

[Retromodo]

Hi all sorry for the late update, thanks for all the help managed to find one locally, £165 including fitting, reconditioned Bosch. All running and charging well now. Thanks everyone for the help

 

[Retromodo]

Thanks mate, appreciate everyone’s help 👍🏻 next job is to find a slight miss… suspect vacuum leak

 

[Retromodo]

First thing is to check the valve gaps, they're almost certainly too close or zero lash .

After that we'll cover diagnosing a miss .

Did valve adjustment year or so ago… will do a new post and update with info 👍🏻