Mercedes W124, not enough juice to run the electrics.

Mercedes W124, not enough juice to run the electrics.

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Discussion

MarshPhantom

Original Poster:

9,658 posts

136 months

Thursday 27th April 2017
quotequote all
First thoughts are it's a dodgy alternator but any other suggestions would be welcome.

Got a brand new Bosch battery in january as I realised the one I'd had on the car since getting it was nowhere near meaty enough (60ah vs 94Ah), things improved after that but I know have the problem that there just doesn't seem to be enough electrical power while the car is running.

Best example is the stereo will cut out and keep doing it if the lights or the heater is blowing. The wiper blades don't work as quickly as they should do.


Thanks for looking.

Peanut Gallery

2,418 posts

109 months

Thursday 27th April 2017
quotequote all
Sounds like a dirty connection between the body and the battery to me..

What voltage are you getting with all electrics turned off but car running?

MarshPhantom

Original Poster:

9,658 posts

136 months

Thursday 27th April 2017
quotequote all
Cheers Peanut, should I check the voltage on one of the fuses?

Thanks.

Peanut Gallery

2,418 posts

109 months

Thursday 27th April 2017
quotequote all
I would just measure across the battery for one test, then check that the voltage between battery terminals is the same voltage as between the positive terminal and a good clean connection on the body of the car.

I confess I only found this problem on my car when I had a slightly larger than normal sound system in the car - still started fine as there was an earth between the engine and the battery, but the connection from the body to the battery was rusty.

MarshPhantom

Original Poster:

9,658 posts

136 months

Thursday 27th April 2017
quotequote all
Sounds like that could well it, the problem only came to light after I fitted some beefier Rainbow speakers. Certainly worth a look

Much appreciated, cheers.

paintman

7,669 posts

189 months

Thursday 27th April 2017
quotequote all
Connect a jump lead directly from the battery earth terminal to a good clean point on the engine. See what happens.

Do the same but from the earth terminal to a clean bare part of the bodywork. See what happens.

If the problem is cured then replace the appropriate earth lead & clean the fasteners that hold their ends to the body/engine.

Common for plastic covered earth leads to corrode to nothing under the plastic sheathing, so whilst the ends look fine there's not aa lot in the middle.

If that doesn't sort the problem then you need to check the alternator output.

LordLoveLength

1,904 posts

129 months

Thursday 27th April 2017
quotequote all
Google OVP relay - responsible for many power and starting problems on Mercedes

MarshPhantom

Original Poster:

9,658 posts

136 months

Friday 28th April 2017
quotequote all
Thanks for the responses so far, hopefully something simple. One of the wires connected to the negative side of the battery had become corroded. Tidied that up and the stereo is now fine.

Cheers, everyone.