Gauge shows overheating but engine is not overheating.when ac is on

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My excursion started overheating several months ago. The radiator needed to be replaced. This was done and a complete system flush was done along with an air lock check. Everything worked until the ac was turned on, then the gauge showed it was overheating but laser temp sensor showed it was not overheating. I had the water pump, temp sensor, thermostat and clutch fan replaced. Vehicle still shows overheating and will go into limp mode but it actually is not overheating because you can take the radiator overflow cap off and laser sensor shows normal temp. I am thinking its electrical. I have not replaced the temp sender yet. It only shows overheating when I turn the A/C on. When I shut the ac off, the gauge goes back to normal. What else can I do?