I noticed today that when I turned my heater on my car temperature gauge flopped over to the stone cold position. Turning off the heater allowed it to eventually creep back up to a more normal appearing position. It’s at home, I’m at work, and I took another car. I will look at it tomorrow. What will I most likely find? I am thinking that it is probably low on water. I am thinking a thermostat problem is possible but less likely. Also, could I actually have been running hot, with low water? I don’t know where the temperature sensor is compared to the thermostat itself. I would assume the sensor is somewhere in the middle or bottom of the engine block, I think the thermostats tend to be on top of the engine block.
Are you saying it went cold and stayed cold even after you left the heater on for a while?
Was this right after you turned on the car? Because I know that my temp guage will “stick” at whatever the temp was when I turned the car off the night before (or an hour ago, when I go to the store) and then drop to the cold end when I hit the ignition, just like my gas guage doesn’t rise to the Full position until I turn the car back on after I fill it up. It “creeping up after you turned the heater off” may just be it getting up to a normal operating temperature (i.e., warming up).
Sounds to me more likely to be a problem with the guage itself. I have a temp guage in my car which randomly dips to zero every so often. I figured out it was a guage problem because smacking repeatedly at the dashboard caused the guage to go back to temp.
Besides, I’m not sure how your car could go from warm to stone cold in a second. Although I’ll let the car experts decide.
I had been driving it for about 30 minutes when this happened. I had had the heater on the whole time, but was stuck in traffic before that. Once I was up to speed and air was really flowing through the radiator is when the gauge fell to cold. When I turned the heater off, it came back up after about 10 minutes.
I’m sure it did not really go from warm to stone cold. Since the gauge worked sometimes, I figured it was not that, but certainly could be. The car is a 1991 Acura Integra with just over 200K so anything could break at any time.
Hmm…the gradual rise back in temperature makes me think that maybe my assessment is incorrect.
Well turning on your heater does disipate some of the heat from the cooling system normally. I was stuck in traffic recently and even though it was hot I put the heater on to prevent the car overheating. It kept it a few degrees cooler and as soon as I got moving the temperature dropped dramatically.
Right, and I have used that trick when overheating in traffic in the summer. However, since I have had the car 14 years, this is definately a new quirk it has developed.
You didn’t mention make or model, but a typical design for car heaters for many years involved the heater holding a reservoir of coolant that is shut off from the engine’s cooling system when not in use. When the heater is engaged, this coolant is passed through the engine’s cooling system and absorbs heat from the engine which, via blowers, is transferred to the interior of the car. The effect you describe can be caused by the not yet heated contents of the heater reservoir being dumped into the engine’s cooling system rapidly when the heater system valves are opened, thus lowering the temperature of the whole cooling system.
Something to remember, as don’t ask mentioned, is that turning on the heater is a temporary save move if you start to overheat in traffic. Moving air over the radiator makes a big difference, as well.
Had a very similar problem a couple weeks ago.
Turned out our radiator had developed a leak and emptied itself out.
The temperature gauge was doing the exact same thing, except our heat wouldn’t work at all, and we had to leave defog on 100% of the time, or it would fog very, very quickly.
Then one day, it go hot enough to turn on a warning, which finally prompted my family to action (after a week of prodding from myself) and it was subsequently fixed.
Luckily there was still 4 days left in the warranty…