temp gauge not working

[hatzie]

Originally Posted by mexlokote

also when i went to autozone to buy the new temp sender unit, they askit was a gauge or light and i told them a gauge so they gave me the temp sender unit and i came home and tried to put it on and it was too big i wouldnt fit so i went back to autozone and i asked and they gave me the light sending unit, and i came home and it fit perfect, i dnt know if autozone has it mixed up or something is going on with my truck because when i first bought it not running, i got it running and one time it overheated and the gauge worked perfectly, this happened after i did a rebuild of engine i unhooked many wires,
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Originally Posted by mexlokote

both wires when grounded make the gauge go to hot it used to work perfectly fine and the temp sending unit is not beside the engine its in front of the engine right where the thermostat is

If either wire nails the gauge when grounded then the gauge is working. You probably have the wrong sender.

The original temp sender is screwed into a hole in the Left Hand cylinder head that's inline with the spark plugs. You prolly have a plug where the sender is supposed to screw in. Using a sender in the intake is problematic because the intake is the high point in the cooling system. If all is well it should read the coolant temp just fine. However. If you develop a coolant leak the sender will be reading an air pocket temp and not the temp of your overheating engine.

The stock temp sender for the earlier builds of these trucks is 1/2-14 NPT. If you have early stock heads the Standard Motor Products TS6 is the right sender. Popular later model heads, like the Vortec, use a 3/8-18 NPT sender. The 3/8-18 NPT senders started to be used in 1986, or a little before, so the Standard Motor Products TS76 or an equivalent should work.

You need to be careful to stay with the 1980's 3/8-18 NPT senders. The stock sender ohms out 13KΏ-34KΏ Cold and 60Ώ Hot. Some later senders, but not all, are the opposite... low Ώ cold and high Ώ hot. Take a meter with you to the parts store and check the Ohmage on the new sender. If the new sender is 13KΏ to 34KΏ cold it'll probably work.