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Weird fuel gauge issues

 
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winddude  



Joined: 15 Jan 2020
Posts: 54
Location: Vancouver Island

PostPosted: Tue Aug 18, 2020 10:01 am    Post subject: Weird fuel gauge issues Reply with quote

I'm having some bizarre fuel gauge issues.

I'm getting the correct ohms at the fuel gauge harness between vi/bk and brown wires, plus I've tested my sender and can confirm the range is good between 80 and 3 ohms. So the wiring and sender look to be good. However my gauge always reads full when the ignition is on, 12v on 15, however the weird part, the fuel gauge reads correctly if I turn the lights on, and shut the ignition off.

I've also disassembled the gauge, and the circuit is clean, with no shorts between circuits. Continuity to the actual fuel gauge from the pin. So I believe the gauge is good. Or could the actual little ohm meter in the gauge be bad? But then I wouldn't expect it to read correctly when the lights are on and ignition off.

Thoughts? Ideas? What else to test? I'm getting 12v on black to the fuel gauge harness with ignition on.
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Eliza  



Joined: 17 Aug 2015
Posts: 65
Location: Prov. Utrecht, The Netherlands

PostPosted: Tue Aug 18, 2020 2:30 pm    Post subject: Reply with quote

I had the fuel gauge reading full ( although the tank was not ) a few days ago, after disassembling and cleaning.

I took it apart again and found when I unbolted the fuel gauge assembly from the circuit board that the little metal cup with the bolt going through the back had come loose from the assembly. This is normally crimped on to 2 of the four contacts on the side of the assembly opposite the needle.

I squeezed the cup back on to the contacts, and secured them with a drop of solder.

Presto, fuel gauge works again.

If needed, I can send you a link to a how-to with pics, although in German Let me know if you think that'd help.

Good luck,

Eliza
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1985 924 NA EUR-spec
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winddude  



Joined: 15 Jan 2020
Posts: 54
Location: Vancouver Island

PostPosted: Wed Aug 19, 2020 4:33 am    Post subject: Reply with quote

That would be great if you can send pics, I'm not sure which cup.

I did have the gauge apart, and everything seemed fine.
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Eliza  



Joined: 17 Aug 2015
Posts: 65
Location: Prov. Utrecht, The Netherlands

PostPosted: Wed Aug 19, 2020 9:48 pm    Post subject: Reply with quote

Here's the link - I suppose it's ok to link? Otherwise, I'd invite the admins to remove this and I'll send the link via PM.

https://www.stinni.de/index.php/porsche/tipps/87-kombiinstrument-instandsetzen

On the fifth photo, left side, you'll see the "cup" I'm on about. The four contacts are on the flipside of the gauge/needle side of the assembly. Verify if everything is still firmly attached to each other - in my case it wasn't, I could lift the round thingy clear off of the assembly.
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1985 924 NA EUR-spec
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winddude  



Joined: 15 Jan 2020
Posts: 54
Location: Vancouver Island

PostPosted: Sun Aug 23, 2020 7:51 am    Post subject: Reply with quote

Thanks, that's what I had done. Oddly enough when I assembled everything this time it worked :s
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Eliza  



Joined: 17 Aug 2015
Posts: 65
Location: Prov. Utrecht, The Netherlands

PostPosted: Sun Aug 23, 2020 5:57 pm    Post subject: Reply with quote

Good for you!

Glad you got it sorted!

Eliza
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1985 924 NA EUR-spec
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