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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: Gabriel70 on July 18, 2020, 02:03:57 AM

Title: Faulty speedometer
Post by: Gabriel70 on July 18, 2020, 02:03:57 AM

Hi

My home is in Melbourne, Australia.
Today, I decided to try and fix my speedometer.
This problem started approximately ten years age when my speedometer became erratic and died within minutes.
I have examined  the instrument cluster numerous times.
Today, I decided to remove the long, thin circuit board located under the speedometer on the bottom right of the instrument cluster.
I examined the board and noticed a very faint burn mark underneath the electrolytic capacitor, located near the green capacitor.
I flipped the board over and noticed a burn mark focused around the electrolytic capacitor.
I removed the capacitor and took a few photos of the board.
I’m now looking to purchase a replacement board.

Regards

Gabriel

Title: Re: Faulty speedometer
Post by: rbm on July 20, 2020, 05:00:37 PM

Hi,

Have you tried to clean the burn off the board and replace the electrolytic capacitor with a new one?  You might also want to replace the green capacitor as well.  It looks to be a tantalum one and they tend to self-destruct over time.  It might work and save you the cost of a new board.

Title: Re: Faulty speedometer
Post by: Gabriel70 on July 27, 2020, 09:52:33 AM

Hi

I replaced the 10μf electrolytic capacitor and the speedo is now working.
I’m not certain how to minimise the condensation inside the gauge cluster.
It’s a 1984 k100.

Thanks

Title: Re: Faulty speedometer
Post by: Laitch on July 27, 2020, 10:27:21 AM

Quote from: Gabriel70 on July 27, 2020, 09:52:33 AM

I’m not certain how to minimise the condensation inside the gauge cluster.

The BMW/Motometer solution to this problem was to make holes in the rear of the instrument case then cover the holes with GoreTex fabric—at red arrows in the attached photo of a later model instrument cluster. That seems to have done the trick. Be certain the case gasket is in the correct position when the case is screwed together. Using a thin coating of flexible silicone sealant on the gasket will help stop moisture penetration.

(http://www.motobrick.com/gallery/3/1601-270720102413.png)