Why does my car run hot when I turn the heater on?

Your engine’s cooling system builds up an enormous amount of pressure. The net result is a searing hot jet of air flowing from the heater vents, and engine overheating as a result of little to no coolant flowing through the radiator.

What causes the temp gauge to peg Hot?

When my car is running, the temp gauge goes and pegs hot, even if the car is cold. I dont know if its a coincidence that I just changed my plugs or what, but Id like the gauge to read proper. What would cause it to peg hot??

What should the temperature gauge be on a hot engine?

With a hot engine it should measure 30-50 Ohms. If you measure around this value (or definitely not near 140 Ohms) with a cold engine then the unit is faulty and needs to be replaced. A quick test is to disconnect the lead from the sending unit, turn on the ignition and observe the temp. gauge.

What to do if your temperature gauge is pinned Hot?

If you measure around this value (or definitely not near 140 Ohms) with a cold engine then the unit is faulty and needs to be replaced. A quick test is to disconnect the lead from the sending unit, turn on the ignition and observe the temp. gauge. If it registers ‘zero’ then most probably the sending unit is faulty.

Is it normal for the temp.gauge to go red hot?

Yes, coolant level is fine! The temp. gauge goes to red hot or pinned as soon as I start the car cold. And…after approx. 15 min. driving locally, the engine doesn’t seem to be overheated. so I’m assuming that the thermostat is working fine. I’m just afraid to drive it longer or farther when the temp. gauge says red hot.

What should I do if my temp.gauge says zero?

A quick test is to disconnect the lead from the sending unit, turn on the ignition and observe the temp. gauge. If it registers ‘zero’ then most probably the sending unit is faulty.