OBC blank

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bmw335icoupe
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Post Fri Apr 23, 2021 9:11 pm

My OBC went blank as per photo attached.
Is it terminal?

At the same time my rev counter stopped working, coincident?

Thanks in advance for any input.
Peter
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Brianmoooore
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Post Sat Apr 24, 2021 10:54 pm

Data for the OBC and the drive for the tacho. both come from the SI board in the instrument cluster, so I'd remove that and check the condition of the batteries.
Reverse lights working?
Interior lights working?
bmw335icoupe
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Post Sun Apr 25, 2021 9:20 am

Thank you very much for your input.

The interior light stopped working over a year ago.

The reverse light worked couple of weeks ago but will check again.

Will check the condition of the batteries this week.

It started with me being ambitious and trying to fix the power aerial.
Removed the boot panel and discovered that the green wire was plugged in but the red one was disconnected so I connected it but that did nothing.
So I left it and went home. Following morning there was a ticking noise coming from the car. The aerial motor was spinning but the mast was down.

I wonder if that motor spinning could have an effect on potentially draining the SI board batteries???
‘91 w124 Mercedes-Benz 300E
`13 F30 320D Saloon
`90 E30 320i Convertible
`91 E30 318i Convertible - sold
`06 E92 335i Coupe - sold
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Brianmoooore
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Post Sun Apr 25, 2021 10:24 am

There's absolutely no chance that the electric aerial's problems are anything to do with those of the cluster and OBC.
However, the interior lights share a fuse with the wire that feeds power to the instrument cluster's batteries, and if this fuse is blown, the batteries will deteriorate, and may eventually corrode and leak some very nasty chemicals over the board they are mounted on. The exact result of this is unpredictable, depending on what parts of the board are damaged, and while I've never known the OBC to go blank because of this, it's not inconceivable.
bmw335icoupe
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Post Sun Apr 25, 2021 10:53 am

I’m going to have a look at the fuse first.
Is it fuse Nr 10?

Than will remove the clocks and inspect the SI board

Thank you very much for your time input

Stay safe
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Brianmoooore
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Post Sun Apr 25, 2021 10:56 am

Fuse 21.
Fuse 10 is reverse lights + a couple of other important things.
bmw335icoupe
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Post Sun Apr 25, 2021 11:22 am

Thanks

Would have been looking in the wrong place....
bmw335icoupe
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Post Sun Apr 25, 2021 7:07 pm

Brianmoooore wrote:
Sun Apr 25, 2021 10:56 am
Fuse 21.
Fuse 10 is reverse lights + a couple of other important things.
Amazing!!!!

I changed the fuse 21 and the OBC came to life as well as the rev counter started working again.

Thanks a lot Briannoooore!!!
Top man

Stay safe!
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`91 E30 318i Convertible - sold
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Brianmoooore
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Post Sun Apr 25, 2021 7:26 pm

Don't celebrate too quickly! You still need to check the SI board batteries - they've been discharged to the point where the board has failed to work, and if they leak, they do expensive damage.
bmw335icoupe
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Post Tue Apr 27, 2021 8:07 am

You are absolutely right.

Will have a look at that soon.

Yet again thank you very much for time.

Stay safe!