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Old 08-14-2009, 10:02 PM
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how do you wire up a temperature sending unit?

i have a 1968 Chevy pickup that i just changed the motor in. i drove the truck for a little over a year w/o a reading on the temp gauge. i need to know if the sending unit uses a ground or a hot wire? and how do i wire up my factory temp gauge, cause i think its not hooked up either.

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Old 08-14-2009, 10:16 PM
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The sending unit grounds the wire from the gauge, showing temp by varying the resistance as it heats up. The wire will be the hot FROM the gauge(single wire).
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Old 08-15-2009, 05:09 PM
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If its an SBC, the sending unit is on the driver's side of the engine, between the two middle cylinders. You can look down see it between the runners of the exhaust header.

The wire will have 12 volts when the ignition is on, and it grounds through the sending unit. If you have 12 volts, and you ground the wire when the ignition is on, it should make the temp gauge go to max.

Look for the sending unit wire in the loom on the driver's side. The stock wire should have a long black plastic connector on the end, with a brass slotted fitting inside. The long plastic piece on the connector is designed to hold the wire away from the exhaust manifold.

Bruce
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Old 08-17-2009, 09:32 AM
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ok, new problem

i grounded the gauge and it went to the max. but still have no clue on my wiring, its not the factory wires, so heres what i tried: i took the post on the back of the gauge that i grounded and ran a wire direct to my sending unit, started my motor and let it run for 15-20min. but the gauge never moved, after i let it run i grounded the wire to make sure the gauge still worked and it went back to the max. should i keep trying to get it working, or should i just install an aftermarket temp gauge?
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Old 08-17-2009, 02:39 PM
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From your description the sending unit is bad, you have proven that the gauge does work when you fully grounded the wire and it maxed out the gauge. Also, these sending units a specific to the year of the gauge AND whether it is for a gauge or an idiot light, they do not interchange.
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Old 08-17-2009, 11:32 PM
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proplem solved

oh ok ic the sending unit was brand new and it was the same type that was in my original motor, but i dont really know the year of the gauge, and to not waste any more time than i already have i just took out the original gauge and replaced it with an aftermarket. thanks for the help.
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Old 08-23-2009, 04:46 PM
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I think that the issue is the sending unit was for a high temp light and not for a gauge. I run both the light and the temp gauge in my Pontiac, there is another plug in the head on the passenger side between the back two cylinders, just pull the plug out and put the temp sending unit in there.

Vic
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