1992 Honda Accord – Fan won’t turn off

A number of weeks ago I had my radiator hose blow and had to replace it. Early this week one day my wife picked up some things from town and parked the car in our driveway. She mentioned that it was odd that the radiator fan would come on after the car was shutoff (which it virtually NEVER did in the past). Immediately I did some troubleshooting. Eventually I found a pattern. When the key was in the ignition and the dash lights were on, one of the radiator fans would shut off. As soon as I turned the ignition off so that the dashboard lights were out, the radiator fan would come on. It is normal for this fan to come on if the engine is hot. In my case the temperature gauge on the dashboard showed that temperature was at half way (which is the highest it ever goes, unless something is wrong like a burst rad hose). After trying different things I could repeat like clockwork, turn off the ignition so the dash lights are off, and the fan comes on… and stays on for more than 15 minutes. I knew something was wrong.

After googling around for my problem I found MANY posts talking about things to try. Here are the steps to try to figure out what is wrong:

1. Under the hood, near the windshield on the passenger side you should see a box of relays, etc. On the cover it will tell you which relay is for the radiator fan. Notice the relay for power steering is the same type as the radiator fan. Try swapping the two (the fan and the power steering) to see if you have a bad relay. Try playing with the ignition and see if the fan goes off. In my case, the relay was fine and was not my problem. You can take out the fan relay in a pinch so as to not drain your battery until you can get the problem fixed. This puts your engine at a slight risk of over-heating because that fan will never turn on. In cold weather it isn’t much of a problem.

2. Check the Thermo Switch. Where is it? Follow the hose coming out of the top of the radiator towards the engine. At the end of the hose you will see a green plug. The thing that plug is inserted into is the Thermo Switch. This tells the fan when to turn on and off depending on rad fluid temperature. Be CAREFUL to get the right part. I read in many postings about the “cooling temperature sensor) which ended up wasting days due to getting the wrong part numerous times from the auto parts guys. Not sure if that is the same as the “thermo switch” but the name on my invoice was 37773-PT3-A01 Switch, Thermo. The price direct from Honda in Canadian dollars was $62.04. Unclip the green plug using a flathead screw-driver (come in from the end connected to the engine or you may break the green plug). Once you get it off, you will require a 24mm deep socket to get the old thermo switch off. Turn counter clockwise to unthread the old one. Rad fluid will leak out a bit (that is ok) once you get it out. Now put the new one in (thread clockwise) and hookup the green plug and voila, no more infinite fan syndrome! This is the most common problem for fans that either stay on or do not come on, a faulty thermo switch.

Here is a picture with the box of relays circled at the top left and the thermo switch circled in the center:

1992 Honda Accord Engine

Hope this helps someone.

12 Responses to 1992 Honda Accord – Fan won’t turn off

  1. Thanks a million! You’re info was what I was looking for. I had a problem with my fan not shutting off. I bought a new relay and that was not the problem. I was getting ready to hardwire it to my ignition to save myself money when I found your blog. I made a trip to my auto store and $20 later problem was solved. Saved me alot of time and a headache

  2. I was getting ready to hardwire it to my ignition to save myself money when I found your blog. I made a trip to my auto store and $20 later problem was solved. Saved me alot of time and a headache

  3. Thanks for the help! The relay fix was a nice alleviation for the evening since I can’t get out to a parts store at this hour. The fan was keeping the whole neighborhood up! And it’s 3 degrees here in Nebraska… I’m not terribly concerned with the engine overheating just yet.

  4. hi, im having that problem as well
    my fan goes on wen i shut off my car and i thought it was normal
    but now i got smoke coming through my padiator cap
    but the tempurture isnt rising in my car
    but it drainz the fluid after a long distance of driving
    do you know whatz wrong ?

  5. So you’re saying steam (or is it smoke) is coming out of your rad cap? You mean it comes out just on its own, or you take the cap off and smoke comes out?

    If steam/smoke comes out of your rad cap, it may be that you simply need to replace the cap (can get a new one almost anywhere including Walmart). That is the easiest thing to replace, but make sure you top up the fluid.

    Check under the hood for leaks (and always carry around with you silver duck tape in case your rad hose blows you can use that tape temporarily to tape up the hole till you get to a service station, if you have enough fluid left in the rad). Check under the car for dripping of rad fluid while leaving it parked for a while.

    The fan coming on IS normal. What ISN’T normal is that it stays on for longer than 15- 20 mins MAX, and will eventually drain your battery charge.

    The worst case possibility is you have a blown head gasket meaning rad fluid is leaking into the engine. To check, pull the oil dipstick out and see if the oil looks greyish and bubbly (as if rad fluid is mixing into the oil). That is expensive to get fixed.

  6. I changed the thermo switch–didn’t help. Checked the relay (although I could not find a power steering relay but the one next to it was the same-) and that didn’t do anything. But tonight as we stood next to the car the fan shut off after about 15 minutes so maybe it just needed to stay on to cool the engine?

  7. Yes it is well known that the fans DO go on after you pull out the key from the ignition and walk away. But they should not be longer than 15-20 minutes max, mine would go until the battery was dead (hours)

  8. so if the relay is not the answer and the thermo switch is not the answer what is? Yesterday the fan was off and CAME ON spontaneously. I really don’t want to have my daughter get off work at 3 in the morning to find her battery dead. help please

  9. First let me say I am no expert, I am an amateur sharing what I have learned!

    You said the fan would go off after 15 minutes. If it does come on after that then you likely still have a problem. If you already changed the switch that I pointed out in this blog, then you may want to consider the other sensor used in the cooling system. This other sensor (is what I originally bought and had to return as it was not the sensor I needed to replace) is the cooling temperature sensor. If i remember correctly this one has a nob (like on a thermometer you put in your mouth) which the thermo switch does not have (at least mine didn’t).

  10. Mark Vejvoda, to unclip the green plug, what did you mean by “come in from the end connected to the engine”? You can’t just pull it straight out with your hand? or do you need the screwdriver to pry it out? Can you please give more details. Thanks.

  11. Simply meant that you lean over the head gasket facing toward the green plug and slide the screw driver under the plastic clip holding the green plug in place. If you are not careful you may break the clip on that green plug as the plastic can be very brittle.

  12. On my 95 honda odyssey it seemed the fan was stuck on. I tried your idea with the relays. The one relay which seemed identical to the cooling fan relay was the power window relay. By the way the windows worked fine. After switching the fan stopped. And the windows still work fine. So now I’m happy the fan stopped but still unsure of what was happening.
    So I just put the relays back in their original positions and it seems as if the problem is gone. Will drive around to see if issue returns and get back to you.
    Thanks for your help.