1991 Honda Civic



August, 4, 2012 AT 4:11 AM

I noticed the other night that my son's car was making a noise four hours after it had been turned off. It was the thermatic fan running. I disconnected the fan temporarily, and now need to find out what is causing it to run constantly.

The car runs cool all of the time, in fact most of the time it is too cold (according to the gauge), I think maybe the thermostat is stuck in the open position, but that is the next issue to deal with.

How do I test what component is causing the fan to run 24/7, I assume it will either be the sensor (located at the base of the radiator) or a relay somewhere under the bonnet.

Many thanks in advance, David


4 Answers



August, 4, 2012 AT 11:34 AM

Check this relay first, if not located as in pic please advise exact model code.



August, 8, 2012 AT 6:07 AM

Hi mhpautos,

thanks for the help, and sorry for the delay in replying. I asked the question when I was 1000 miles away from my sons car, now I am home.

OK, the relay you pointed out is the cooling fan relay, but not the correct one in my case. The fan that runs 24/7 is the smaller fan next to the cooling fan.

I am not sure I got it right when I explained the situation originally. 2 fans, the bigger one(LHS looking from the front) works normally, seems to come on only when the air conditioner is turned on, the slightly smaller fan (RHS)supposed to come on when the car gets hot, and also when the air is turned on, that is the one one running all the time. I found the relay for that, it is one of two located at the front of the engine bay. So I disconnected that relay, reconnected the fan at the fan, and it is definitely the right relay, as the fan stayed off. Reconnected the relay, and it all works normally now, fan comes on when air on, comes on when temperature reaches a certain point, and goes off when engine cools down or ignition is shut down.

So, obviously whatever was causing the problem has gone away, but I fully expect it to return. So I have purchased a new thermo switch for the bottom of the radiator, but can't find any details on the relay.

Can you give me a part number for the relay, or should I just buy one from Honda?

Many many thanks again for your help.




August, 8, 2012 AT 6:10 AM


just noticed you are an aussie, like me, I was in adelaide over the weekend, now back in brisvegas. Thanks very much for the help.



August, 8, 2012 AT 9:26 AM

Yeah, only Aussie working here, was the first non US tech they put on, best to give the VIN to Honda that way they will get the correct relay, often they can act up due to loose terminals or a bit of corrosion in the plug, but a new one should do the job for you. That pic would have been for a US origin car as well, most work comes from the US but often I just don't know unless they give a clue in the question, can make it interesting.

Cheers, Mark.

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