TAC Tech => Electrical => Topic started by: Seven on March 21, 2021, 07:30:56 AM
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I took my 1979 301 4 speed out for the first time this year and noticed the the water temperature gauge was not working.
What's the best way to determine if the problem is with the gauge or the sending unit?
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First make sure the wire didn’t pop off the sending unit. Then when your ignition is on be sure the gauge is at or goes to full cold. If so, ground the wire that goes to the sending unit. The gauge should peg hot. If so, it’s probably the sender as the gauge is working, if not, gotta troubleshoot the gauge.
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X2 very easy to do and accessible. You also want to make sure you have good contact and the sender terminal is not corroded.
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I have similar problem but my gauge goes all the way hot (but the motor is cooling fine), so you say it is the sender? Is there an easy way to identify what the sender is?
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The engine wiring harness only has about 7 circuits, and the temperature sender is going to up on top of the engine, so it's pretty easy to find. The wire is green. Sender will either be on the crossover at the front of the intake manifold, or else reasonably high on a cylinder head.
"Hot" means you have a lot of electricity flowing through the sender wire compared to how much you have flowing to ground under the dash. There are two electromagnets in that gauge that fight against each other. The sender is really easy to test, but the rest of it, not so much.
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I tested the gauge by grounding the sending unit wire and no movement on the gauge needle, is there a gauge fix (searched all over several forums with no luck)?
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They are very common to find used, possibly even new now but part of a large cluster package. Most will say, unsure if works, untested, worked when taken out, all of which may be accurate but not tell you if will work when you get it so still a lottery but most are good. Look for units that are clean, have good condition faces and readings, no rust on case, font matches your unit, that sort of thing and you may get lucky, or at least some nice spares. Temperature sender units are also cheap, doesn't hurt to grab another even as a spare.
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"Cheap" is a relative term, new temp gauges all seem to be priced the same and by the time all is paid I'm looking at $300ish Canadian that's why I want to try and repair my original if possible.
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That's why I said temperature senders, not gauges. I'm also well aware of the costs of shipping several faulty items individually overseas in an attempt to avoid paying for the new item which still ends up being the case. Did that with the Tacho.