Hi, I didn't see anything like this, so I hope its not a duplicate issue. 2000 Accord V6 Automatic. Been running fine, but tonight on a not particular hot day, the temp gauge pegged and the fans stayed on for a LONG time after the car was shut off (this was my Son's story). I came home and tried to duplicate the issue. The car had completely cooled, I checked the coolant and it seemed OK. I started the car and it ran normally, I let it run for 10 minutes or more and the thermostat had yet to open as the radiator was not hot. The temperature gauge was about mid way which is normal operating range for this car. So, I figured I would take it for a ride. I got not further than 7 houses down the street and the temp gauge went straight to pegged at Hot. The car seemed to run fine and didn't really seem possible that it would jump like that. I feel like I could have let it sit in the driveway idling forever and it would have stayed mid way between C and H. I took the car home and when I shut it off, the fan at the rear of the engine came on. Just that one, the other one never came on. With the engine off, the fan stayed on for at least 15 minutes. If I turned on the key (not starting the engine) the fan would stop and then start again, once I turned off the key.

It doesn't seem to me like the car was really hot, and I believe the thermostat was open in that the radiator was warm.

Bad thermostat? Doesn't seem right to me. If the fans are controlled by the temp sensor, I kinda suspect that. It seems logical that if the bad temp sensor was bad, it would peg the gauge and trigger the fans. But why would this happen only once I started driving it?

Thanks for the suggestions!

Mike

 

once you put the car under a load it has to work harder!when you turn the AC on,turn the heater on,turn the lites on,is putting the car under a load.
when its cold warm it up let it idle and turn the AC on,see if the temp rises?when you turn the AC on the AC fan will also come on thats normal,when it reaches normal operating temp the cooling fan should come on?if both fans are working normally an the temp gauge rises above normal,or high then it may well be the thermostate?
when its running at normal operating temp and if an when the cooling comes on check the return radiator hose,it shuld feel hot if not the thermostate is not opening

 

This is some information regarding the fan operation with the fan control module and thermo-switches (aka fan switches).

The V6 has a radiator fan control module under the right side of the dash. The module controls the fan relays via the thermo-switches.

Thermo-switch A (#14) is located on the thermostat housing. It sends a ground signal to the radiator fan control module when it reaches ~ 190 degree F, at the same time activating the fan relay which would start the fan operations, when engine is running. It should shut off around 180 degrees F. To check fan switch A, unplug the green electrical connector and jump the connector with a wire or small paper clip. Turn ignition to ON, both fans (A/C condenser fan and radiator fan) should come on.

If the A/C is turned on, both A/C condenser fan and radiator fan should turn on, regardless of coolant temperature at the fan switch.

Thermo-switch B (#10) located on the left of the front cylinder head turns on the fans at ~ 225 degrees F. It grounds the fan switch B terminal in the radiator fan control module when engine is not running, so power is supplied to the radiator fan relay to turn on the radiator fan.

#13 is temperature gauge sender and #15 is the ECT sensor for the ECM/PCM fuel/ignition data.


Right now, your problem may be the thermostat not fully opening. The radiator hose from the thermostat housing should feel warm to hot if the thermostat opened. If it doesn't, it means the thermostat didn't open or is only partially opened and not allowing coolant to flow from the engine block back to the radiator.

 

Easy fix! It was dark (and late) last night when I posted the problem and I was not able to fully troubleshoot. I did fill the overflow tank last night and when I started looking at it this afternoon, I noticed it was empty again. Hmmm, not enough water? Yep. I filled up the radiator while the car was running and filled the overflow and about that time the thermostat opened. Upper hose got hot, warm water flowed in the radiator. All things one would expect.

Drove the car, ran the heater, ran the AC and the needle stayed right between C and H. I did notice that it looked like there was no coolant, so that will be something I do this weekend.

Thanks for the suggestions everyone, turned out to be a kid that doesn't watch fluids. Well, he knows a lot about beer, but that's another story!

 

I'd kind of be worried about a coolant leak. I would want to test for leaks (several methods) to be sure.