Hey guys, I've noticed that my engine cooling fan keeps cycling on and off (and on and off and on off lol). This happens after driving the car, however it's not particularly hot, it certainly isn't overheated.

Sometimes it only runs for a second or two, then turns off, then back on almost immediately. There seems to be no rhyme or reason to it doing this.

Any ideas? Thanks in advance.

 

Can you provide us some basic info on your car, like year, V6 or I4 engine, automatic/manual transmission, LX,DX,EX trim?

 

Haha sorry, 1996 Accord LX coupe, 2.2L/manual.

 

This is only after shutting off the engine, right?

Try unplugging the temperature switch in the upper radiator-hose nozzle at the head. That one is supposed to have authority to run the fan (only one of them) after the engine is switched off. It's supposed to have a deadband of several degrees, to prevent it from switching on/off/on/off with small changes in temperature. Maybe the switch is becoming flaky.

If it does this with the switch unplugged, let us know for other troubleshooting...

Here's the story.
The fan switch in the thermostat housing (LOWER radiator hose back sorta under the throttle body) has authority to switch both fans together, while the engine is running. Presumably that one works OK, but you can check it if you want (let us know).

After shutting off the engine, the fan switch in the upper hose nozzle has authority to run the one fan for some period of time.

There's a "fan timer module" that sorts out the 2 switches, and only allows the fan to run within some period of time after turning off the engine. That's to prevent a bad switch from draining your battery.

 

Thank you, Jim, for all the good information and suggestion! I will try that the next time I get home after a drive, and report back what I find out.

 

Well, wouldn't ya know it, it has stopped doing it now! Haha. I will report back when or if it does it again.

 

That front fan switch is set for a higher temperature. Normally it's during summertime when the heat in the engine compartment causes that nozzle to get hotter than normal a couple minutes after you turn off the engine.

Meanwhile if you want you can check out the fan-timer, and the rest of the circuits.

Unplug the switch back in the thermostat housing. Using a paperclip, jumper between the 2 terminals in that wire. With the engine running, you should have both fans running (don't get caught in the spinning fan). If you feel like it, remove the jumper & the fans will stop. Put it back in & they'll run again.

Plug that wire back together. Then immediately after turning off the engine, unplug the one in front in the upper hose nozzle. Jumper that wire, and that should make one of the fans run. Stop the fan by removing the jumper. After a few minutes try again. Each time, it should make the one fan run. After something like 10 or 20 minutes, jumpering that wire will NOT make the fan run any more (unless you turn the key on which resets the timer).

Anyone know how long the timer allows the fan to run? I'm guessing no longer than 15 or 20 minutes.

 

Do you know what temp your coolant is at when it happened. If it's over 223F the fan timer should run for about 15 minutes and 18 seconds. The fan going on/off randomly while the ignition is on/off then either the radiator fan timer or fan relay is bad or possibly a bad connection somewhere if it's running more than the set time.

 

Jim! Thank you so much for your advice. I followed your instructions in your earlier reply and confirmed that it is the upper temp sensor. I ordered a new OEM Honda replacement just a few minutes ago.

Thanks again!

 

Nahh, it isnt running for excessive amounts of time, it just comes on and off for a few minutes after the car has been driven. The car definitely isnt running hot, nor has the ambient temperature been high when it's doing this. I'm 98% sure it's that temp sensor, but if it isnt for some reason, I'll report back. I'll update this thread when/if its resolved, as well. Thank you and Jim both.