Temperature Fluctuation

Okay, this problem is actually on my mom and sister’s car but seeing that it could happen to any car, I was hoping you guys could help me out.

My mom has a ’97 Corolla and my sis a ’97 Eclipse. When my mom is driving she says that the temperature gauge fluctuates. Whenever she turns on the heater then it would go down but she turns it off then it would go back to normal and sometimes go a bit higher. Then when she starts driving it’ll sometimes go up and sometimes go down. No real pattern. Same thing with my sister’s car. Any thoughts on what it could be???

Probably just a faulty gauge. Sounds like something with the wiring/electricity.

Could be a few things.

I'd check to make sure the fans work properly on their own, not just when the AC is on.
Could be a bad thermostat or possibly a failing water pump.
Could be a faulty temp sensor or eroded wiring.
Could be air or blockage in the radiator.

I'd start by checking out the fans, and wiring to the temp sensor, then maybe swapping a t-stat and flushing the radiator.

Well on my mom's car, the blower unit actually went out not too long ago and we had that replaced. I'll check the wiring to the temperature sensor tomorrow when there's light...but umm...what's a t-stat? Thermostat?

yep