Heat gauge

I have a 95 Monte Carlo with a 3.1 engne.It blew a head gasket then had a rod knocking.I had the engine rebuilt.Before,the heat gauge worked perfect staying at just under the half mark.After I got my car back,the
gauge reads 3/4 before the fan comes on.I took it back to the mechanic and he checked everything out.The engine is NOT getting hot and all the grounds in the wiring are good.He replaced the sending unit AND the temp senser...which doesn't have anything to do with the gauge,and it still reads wrong.I replaced the whole gauge cluster with a known good one and it still reads hot.I unplugged the sending unit and grounded the wire and the gauge pegged hot,so I know the gauge is good.What made the original sending unit go bad? And could the new one be bad too?
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When they rebuilt the engine I'm sure that:
1- They bored it out, that will Make the engine run a little bit hotter, in most cases negligible.
2- The factory gauge is not a good indicator of engine temperature.
3- Just because your original gauge sensor, I'm not sure if that works off a sender, or the CTS, does not mean a new sender will read exactly the same.
Go to a Dollar store, and get a cheap roasting thermometer, and check the actual temperature.
I hope this helps.
RK

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I thought the same thing,that it was bored and that was making the engine run warmer.The mechanic used a gun that measures heat and everything measured 198,it has a195 thermostat.The fan came on around 210
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That's what you want.
RK

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I want the gauge to read right like it did before the rebuild.
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hungry 103 wrote:

reading wrong not the engine running hot. Of course factory gauges are typically very inaccurate, and it's possible that the gauge was reading low before and is reading correctly now. It's unlikely that the sending unit and a new one are both bad, so it's more likely that the gauge is reading right now and was reading wrong before.
--
Cy Welch
89 Camaro RS 5.0 TBI
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