I have "91 Accord SE that has a coolant fan that will randomly start with engine ignition off whether engine is hot or cold.

I have switched fan relays to no avail. If I pull the relay the fan will stop and when I replace it the running resumes.

I have removed the fan temp. sensor and tested with heat to see if the circuit would open and close and it did.

I'm at a loss. Any suggestions would be appreciated.

If the fan comes on over night it will kill my battery.

 

This will sound stange but how old is the battery? Also be sure the battery cables are clean and tight on the battery and I would also clean the "other" ends of the Neg cable where it connects to the body and then to the trans.

 

when the fan starts with the key off, unplug the fan switch that is located in the head closest to the upper radiator hose

if it still runs, it's probably the fan timer unit

 

I replaced fan timer (under drivers side dash) with a used one and that corrected the problem.

 

Check your thermistor should be close to the radiator with electric wires coming off next to your radiator hose. Mine is out so I hooked mine to my battery on purpose to have it always run.