Converted 65 instrument cluster to 66 5 gauge cluster but have wiring problem!

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THE23MAN - 10 Feb 2006 17:41 GMT

I have a 65, 289 A code 4spd fastback that I restored into a correct 66
Shelby GT350. However when turning the car on all the gauges go to
maximum! Ground issue? We have checked all the wiring and actually
have replaced the underwire dash harness with a brand new one and still
have the same issue. The 5 gauge cluster is an original set. Any
ideas?

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Backyard Mechanic - 10 Feb 2006 21:09 GMT

> I have a 65, 289 A code 4spd fastback that I restored into a correct 66
> Shelby GT350. However when turning the car on all the gauges go to
> maximum! Ground issue? We have checked all the wiring and actually
> have replaced the underwire dash harness with a brand new one and still
> have the same issue. The 5 gauge cluster is an original set. Any
> ideas?

With the senders disconnected?

And you see 5v average, {sweeping} at the Voltage reg?

With batt unhooked, OHM out one at sender connector, like the Oil Pressure,
work backwards.

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THE23MAN - 10 Feb 2006 23:37 GMT

I do not understand your message. Could you please repeat as we are
desperate and cannot figure out what the issue may be. Thanks so much!

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.boB - 11 Feb 2006 00:34 GMT

> I have a 65, 289 A code 4spd fastback that I restored into a correct 66
> Shelby GT350.

And I have a 82 Bonneville that restored into a correct 64 GTO.

The gauges are really nothing more than an ohm meter. The sending unit is a
variable resistor.

There is a voltage regulator on the back of the gauge cluster that stabilizes gauge
voltage to a constant 5v. It looks kind of like a circuit breaker. Did you bypass
that during the re-wiring? Check and make sure that the gauges are only getting 5V.
If there is 12V, the regulator is bad.

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.boB
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1966 Mustang Coupe - Daily Driver
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THE23MAN - 11 Feb 2006 01:07 GMT

Yes we bought a new voltage reg (the small one that you referred to)
and still not working correctly! Any other ideas???

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.boB - 11 Feb 2006 18:00 GMT

> Yes we bought a new voltage reg (the small one that you referred to)
> and still not working correctly! Any other ideas???

Check it out to make sure it's working correctly. SHould have 12V in and 5V out.

Then check the gauge wiring. Make sure there's 5V into the gauge, and 5V out.

Remove a post from the gauge and see if there's a direct short to ground.
Sounds like there's a common ground wire that's shorting all the gauges at the same
time.

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