Radiator fan won't shut off when car is turned off
 

I have a 1997 honda accord se 4cyl. I recently had a leak in my upper radiator hose which I replaced. It was leaking on the engine side of the hose. Now when I shut the car off the radiator fan (passenger side) will continuosly run. It used to run for a few minutes and then shut off but now I have let it run for up to 25 minutes and it won't shut off unless I turn the key, pull the fuse (#9 condenser fan) or unhook the battery. When I pull the cooling fan relay, it will also shut off, but turns right back on when plugged back in. Car doesn't not seem to run hot, gauge gets to normal level. It also happens when the car is completely cold just by the click of the key. Any ideas? Thanks

There's a fan-switch in the upper radiator-hose nozzle at the cylinder head. There's also a "fan timer module" somewhere under the dash, behind the glovebox (sorry to be vague but I never owned a 1997). That switch & timer, are responsible for the fan running after the engine is turned off. I don't know how long the timer is supposed to go before shutting off the fan even with a failed switch.

Try unplugging that fan-switch where the upper hose connects to the head (check whether you need to clean antifreeze from that plug). It acts like that switch is stuck closed, or the timer module is bad. Or both...
- The fan running when you first turn on the key (cold engine) points to a bad switch.
- The fan running for a LONG time when you turn off the engine, points to a bad timer.

Is there a way to test both of those parts to see if they are bad? I pulled off the switch and wiped a little residue and plugged it back in. Still had the same results. Also, I don't have to turn the key completely and start the car for the fan to turn on, just have to turn it to the second position on the ignition.

Do you have a multi-meter? Set it for continuity, and check for continuity across the 2 pins of the switch. The switch should NOT have continuity at room temperature. The switch will "turn on" and have continuity when it's hot. Sorry I don't know what temperature, but the proper test is to remove the switch and stick it in a pot of water with a thermometer. Heat it on the stove and it should switch on at a certain temperature, maybe 200 F or whatever the proper value is.

What happened if you unplug that switch? Does the fan still run when you turn on the key? If YES, then the timer module is screwed up. The other test for the timer is to use a wire (or paperclip) to short between the 2 sockets on the wire for the upper fan switch. Turn on the key, turn it back off, and the fan should run. But I don't know how many minutes before the timer is supposed to shut off the fan - it might be longer than 25 minutes.

My 91 accord started the same thing 5 days ago. I removed the relay inside the fuse box in engine compartment. With the Covid I don't drive much. I will test the fan switch as Jim mentioned. Thanks, Ted