I have a question. Is it possible for the engine fan to start running on my honda civic while the car is turned off and has been off for hours? My husband claims that it was so hot in the garage last night that the fan on the car started running. I think it was the house air conditioner that he heard, but he insists it was the car engine fan. I think he’s up in the night!! So…is it him, or me, that’s up in the night?! 
On some cars the fan is allowed to turn until the engine cools off, even with the ignition key out. My Saabs were that way. They’d run for a good 5 minutes, after I was long inside the house.
That garage would have to get really wicked hot for them to turn back on, though. Where is it located, on the sun??
If the car has been off for hours, the engine fan shouldn’t start up. I suppose if the relay that controls the fan is defective, the fan might start up. However, garage would have to be so hot that the engine block would be heated to over 220 F degrees for that to happen and I don’t think that is possible. Therefore, either the relay is defective that controls the engine fan or he heard something else.
I have heard noises that have fooled me in the middle of the night. Things seem to sound different. Our neighbors years ago went through the same problem you and your husband are having. The husband insisted that he heard someone trying to start their car–a 1952 Nash. On those old Nash cars, you could operate the starter without turning on the ignition key. The starter was operated by depressing the clutch and then giving it a final stomp to close the starter switch. The wife was certain it was the sump pump in the basement. To solve the debate, the next night the wife left the keys in the igniton switch to help the potential thief. I think she won–the car wasn’t stolen.
The Honda does turn on the fan after the engine is shut off if the coolant rises above a certain temperature as pointed out by RemcoW, but that is on a timer and will not turn on when the ignition has been off for more than 10 minutes, no matter how hot it gets.
Thanks for your comments!! We do live where it’s hot…but NOT quite so hot as living on the sun!! Now I’m certain that HE is the one “up in the night!” Thanks!
I wouldn’t dismiss what he heard out of hand.
Maybe have him open the hood next time he hears it to make sure it isn’t the car.
There’s an off chance there’s something wrong. Not that it would harm the car but it could potentially drain your battery, if the fans are allowed to run all night.
could a load test on the relay, or even just the battery, tell if there’s something wrong?
Sure but opening the hood will tell you right away, though.
I’m not even suggesting anything actually is wrong - just that he may want to make sure that it wasn’t the fan running so the battery won’t leave him stranded one morning.
My bet is that it wasn’t the car’s fan he heard.
If it doesn’t happen until hours later after it’s shut off, a load test would be quicker than waiting around to hear the engine. A test showing everything is ok now might make hubby think it really was something else he heard