faulty fuel/tacho - Instrument Cluster Repair - Faulty Electrolytic Caps
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Thread: faulty fuel/tacho - Instrument Cluster Repair - Faulty Electrolytic Caps

  1. #1
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    Icon1 faulty fuel/tacho - Instrument Cluster Repair - Faulty Electrolytic Caps

    I recently had to take my instrument cluster out of my s1 405 mi16 due to two problems;
    Fuel Gauge and warning light not working
    Tacho intermittent

    After removing cluster and partial disassembly i noticed many Electrolytic capacitors on the fuel gauge circuit. These can dry out over time and cause faults in the circuit. (30years is a common lifespan but can be less with a cars more harsh environment)

    I had also just received an electronics component tester that week, so i promptly removed a capacitor (noting its installation position - Electrolytic caps are polarized ie positive and negative terminals) and tested - It was way out! The rest that i removed in the fuel gauge circuit ranged from bad to f^%ked.

    I also replaced the one cap on the tacho board, plus the several caps on the temperature(?) gauge board while i had it apart. Tacho cap was stuffed. About half or less of the temp gauge board caps were stuffed. This board was also double sided so required more time & precise soldering.

    I had all the caps in stock (from amp repairs/upgrades) Some of the original caps were 63v, yet i have used only 50v due to my suspicions there is nowhere near 63v in the instrument cluster and was probably done for increased lifespan from the higher voltage larger cap. All caps used were 105 degree and of high quality (ie Panasonic FC & Wima MKS [the two red ones])

    If you are confident then have a go.

    Use automotive rated capacitors (ie Panasonic FC) Use only rated voltage or higher.
    105 degree rating will ensure a longer life.
    Mark PCB before removal of capacitor.
    Remove and replace one at a time so as to not forget value....
    Double sided PCB needs advanced soldering. In most cases soldering from the one side will flow through to the other but this must be visually confirmed.
    Desolder carefully. High quality braid works well ie GOOT from jaycar. The hand squeeze pumps are great for an initial suck. then clean the rest up with braid.
    May take anywhere from 2hrs+ depending on your skills.

    This may not be a thorough post but just wanted the info available to others.

    Most electronics repair shops will be able to do the capacitor replacements, or if you would like me to do the repair, just PM me.

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    dimistyle and PeterT like this.
    89 Pug 405 Mi16
    Possibly for sale....

    WRECKING/ Parts Car:
    Blue 89 405 Mi16

  2. #2
    1000+ Posts REN TIN TIN's Avatar
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    Yes, you can count on bloody electrolytics failing eventually. At lest the boards aren't all SMD, that would be fun.
    Did you consider replacing the electrolytics with tantalum capacitors?
    Yes, they cost a lot more but are more robust and reliable and if there's only a dozen or so involved shouldn't cost too much.
    "I cannot help but notice that there is no problem between us that cannot be solved by your departure. Mark Twain"

  3. #3
    Fellow Frogger! dimistyle's Avatar
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    Nice job with the cap replacement and thanks for sharing

    Sent from my SM-G900I using aussiefrogs mobile app

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    Quote Originally Posted by REN TIN TIN View Post
    Yes, you can count on bloody electrolytics failing eventually. At lest the boards aren't all SMD, that would be fun.
    Did you consider replacing the electrolytics with tantalum capacitors?
    Yes, they cost a lot more but are more robust and reliable and if there's only a dozen or so involved shouldn't cost too much.
    I didn't consider tantalums mostly due to not having them on hand, which is due to not using them for amplifier repairs.
    I don't think they are stocked much through RS Components either. I think this may be due to the environmental impact but dont quote me!

    On the other hand, polyester caps i thought are just as reliable (WIMA MKS used in the std motronic ECU) and are also super long life.
    I used 2 of these on the fuel board as i had them on the shelf.

    My other train of thought was, the new caps should last another 30 years. Too far away to think of what might be!
    89 Pug 405 Mi16
    Possibly for sale....

    WRECKING/ Parts Car:
    Blue 89 405 Mi16

  5. #5
    1000+ Posts REN TIN TIN's Avatar
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    Fair comment. I don't know about you but I won't be around in 30 years even if may current cars are.
    "I cannot help but notice that there is no problem between us that cannot be solved by your departure. Mark Twain"

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