SL/R129: 91' 30sl electrical problem

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Nov 4, 2016 | 08:18 AM

mrSL

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91' 300sl

91' 30sl electrical problem

Hey,
Recently I noticed a very odd problem in my SL, When I use my turn signals all the dash lights come on, gauges reset, and then return to normal.
I should mention that the battery is brand new and the car has barely driven.
I know that there isn't no magic fix to it, but where should I start my troubleshooting?

Thanks

Nov 4, 2016 | 11:13 AM

mrSL

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91' 300sl

Quote:

Originally Posted by Plutoe

Start with the relays!!

What relays?, what does relays has to do with the problem I described?

Nov 4, 2016 | 11:50 AM

mrSL

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91' 300sl

Quote:

Originally Posted by Plutoe

You obviously don't know your very old car----get off the couch and search for wiring diagrams and then lift the hood you will find loads of turn\wiper relays---grounds bla bla!!-----remember you asked---"Where to start"

You obviously don't know a lot about any electrical troubleshooting , components and there way of operation , if you would have, you would suspect that a voltage drop/a blown cap at the instrument cluster/ a short and etc.. can cause the problem, I agree with you that poor relay connection can lead to a voltage drop, but it's very unlikely. So in that case I wouldn't mislead others, like you did.

Nov 4, 2016 | 04:58 PM

bobterry99

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From: Atlanta, unfortunately

'09 S600, (2) R129 300SLs, '03 SL500, '03 SL55

Quote:

Originally Posted by mrSL

...When I use my turn signals all the dash lights come on, gauges reset, and then return to normal.

This is a common problem, and the solution is well-established: remove the cluster from the vehicle, open it up, and replace the 470uF capacitor on the main circuit board. It is by far the largest capacitor on the board, and it is impossible to confuse it with anything else.

Don't waste time even thinking about a relay.

Nov 4, 2016 | 05:48 PM

mrSL

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91' 300sl

Quote:

Originally Posted by bobterry99

Thanks a lot for your reply. From my understanding and research, there are three caps on the cluster pcb, since the unit will be apart already, I figured it will be a good idea to replace all of the three, I couldn't figure out the values of the two additional caps, Are you familiar with their values?
Is there any guide for removing and disassembling the cluster?

Thanks

Nov 5, 2016 | 10:55 AM

bobterry99

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From: Atlanta, unfortunately

'09 S600, (2) R129 300SLs, '03 SL500, '03 SL55

Quote:

Originally Posted by mrSL

Are you familiar with their values?

They are probably used in a role where any value above a minimum value works fine. I'll guess 100uF will work fine.

Disassembling the cluster is completely intuitive. No special tools are needed. Nothing at all tricky about it that I can remember.