Chris Fonock

Help. I have a 2009 Honda civic that is running the battery dead from the radiator cooling fans not turning off after the ignition is turned off. I have replaced the relay and ECT sensor and the problem still persists. The problem seems to be intermittent. Took it to a mechanic wouldn't act up for three days. Picked up the car and what do you know, problem is back again the next day. Frustrated

ezone

Which fan stays on? One or both? Which one, if only one?
WHich relay was replaced? (of the dozen or so in the box, or the other dozen in the rest of the car)

What trim is the car, LX/EX/Si?

Chris Fonock

Both fans were staying on, I replaced the cooling fan relay I believe. When I pulled the relay initially the fans shut off so I made sure I replaced that one. The model Civic is a LX-S. Thanks for the quick reply. I had a taken the car to a trustworthy mechanic and he could not diagnose anything because the fans would never stay on after the ignition was turned off. The car was parked last night and the fans ran all night of course after I picked up the car from the shop.

ezone

Looks like there's 3 relays that have to do with controlling the radiator fans,

one relay for each fan, and a 3rd relay that switches the fan motors from direct circuits to series circuit for "low speed" operation,.

Radiator fan relay (the one I suspect is sticking on, #15 in the diagram below)
Fan control relay (#4)
Condenser fan relay (#3)

Most likely: At least one of the relays (if not more) are sticking on. (Again, I suspect the #15 radiator fan relay)
IF you get the fans stuck on, tap on top of the relays and the stuck one will probably release and the fans will shut off....but a stuck relay may release if you tap anywhere near it so it may not be real evident exactly which one it was.....


What may have happened in the past:
One of the more common relay problems was a sticking compressor clutch relay (position #12 in the diagram below).... if someone just swapped random relays trying to find a good one, maybe the bad one was swapped for testing and you found what component it got swapped with.
Ya know, these things do happen.

The Omron brand relays are used all over the car to control many different things....most of the time they aren't a problem-- except when used for the compressor clutch (thus, an improved/updated relay was released for that specific problem).

Updated relay brand is MITSUBA, it can handle more electrical load than the Omron brand
Honda part number for the Mitsuba relay is 39794-SDA-A05. (Right now this one is about $20 MSRP unless your local dealer marks up their parts a lot.)
Original (failure prone) relay brand is OMRON
Denso is another brand you may see in there but it's not been real problematic IMO. That doesn't mean it can't be a problem at all, but it's not real common to see a problem with one.

Cheap $4 replacements from parts stores....anyones guess, there's a reason they are cheap.

Chris Fonock

Thank you so much for the help. I will try to replace the other relay and see it goes. I really appreciate the valuable information and prompt reply to my thread. Have a great day!