I have a honda accord 1997 automatic VTEC. Recently, i experience this overheating of engine while driving because the temperature gauge needle is moving up going to the red zone. So what i did is to stop the car
and opened the hood. I found out that theradiator fan is not turning even if the temperature is already very very hot. I turned on the AC and found out that both the AC fan andradiator fan turned on. I turned off the AC.
But because the temperature is approaching the red zone, i had to turn off the engine. I noticed that by the time i turned off the engine, the fan suddenly turned on for about1 or 2minutes. After some time of cooling
down the engine, i opened the radiator cap and found that the water level is ok. so i discounted any water or coolant leak in the system.

With this experience, what could be the problem? i called a friend and asked what could be the problem, he said that it could be the thermostat. he doesnt know though if where it is located. for the 1997 honda accord, where is the thermostat located? is it the one connected to the upper radiator hose or the lower radiator hose?
I tried to short the switch (green switch)that is connected to the upper radiator hose but the fan did not turn on. but shorting the other switch (also a green switch)that is connected to the lower radiator hose at the engine side turned both the AC and radiator fan on. I also noticed that the upper radiator hose is very very hot, while the lower radiator hose is cold or barely warm to the touch. hope somebody could advise me of other possible problems with my car and corresponding troubleshooting. the inset picture shows the orientation of my engine. the lower portion of the picture with the green switch is the upper radiator hose. the upper portion of the picture with another green switch is the lower radiator hose. thanks for the help.

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In your picture there's a green plug at the top & another at the bottom. Those are the 2 pressure switches to turn on the fans.

The one at the bottom (upper radiator hose) is responsible for switching the fan after you turn off the engine. It seems to be working OK.

The one at the top of the picture is responsible for switching the fan while the engine is running. That makes your fans run, so the system is OK and itSEEMS like a bad switch.

That housing (lower radiator hose, top of picture) is where your thermostat is located. The thermostat itself doesn't tell the fans to run, but the hose temperatures looklike your thermostat is stuck closed.

I would replace the thermostat. I think it's stuck closed, which causes the lower radiator hose to be cool. That in turn causes the fan switch tosee arelatively cooltemperature.

While it's open, you could also remove that fan switch & stick it in a pot of water. Heat up the water & monitor the switch with a multi-meter. When the water gets hot the switch should close & the meter shows continuity. If it doesn't then you ALSO have a bad switch.

 

There is a thermoswitch A on the thermostat housing below and behind the distributor which is likely your problem. It should close and cause the fans to run when temp reaches about 195F. A new switch may fix the problem.

Cooling fans running while engine is OFF is normal if coolant temp is high when shutdown.

However, I have found that as long as vehicle is moving forward the coolant temp will not overheat. If you are overheating while driving, you may need a new radiator orthermostat.

Thermostat is a relatively simple replacement, and might be a goodinvestment when replacing the thermoswitch A.

A search for thermoswitch should uncover more information. See "Overheating" link in DIY section.

good luck

 

Thank you very much. I will try all your advice. Will give you feedback of the outcome. Thanks again.

 

I would also agree replace both switch and thermostat.. Not a hard job to do.. Let me tell a story about my 2000 accord overheating problem though, once my car did say thing fans would only turn on with a/c.. Let car run and felt pressure and flow (heat) thru both upper and lower and verified thermostat was opening.. next i hot wired the switch going to the fan , the fan turned right on .. So at this point i removed switch and tested with multimeter while using a light to heat up just a couple seconds till it heats up pops and current can flow thru.. so i was like umm ok not the switch.. Now meanwhile prior to this i pulled off the cap of radiator and saw plenty of coolant, also resivoiur was full ..Come to find out i add about 12 ounces of water to radiator and switch works fine .... like the wate was never touching it or something.... thats just my 2 cents

 

New guy here. just wanted to thank this forum and its members for the excellent advice given in repairing our Accords. I searched the overheating problem that my 2000 Accord EX 2.3L AT was having. I recently replaced the transmission and it began to overheat afterwards. I had topped off the radiator with coolant after replacing the transmission and had made sure that all of the connectors were hooked up and secure so I was quite frustrated that this problem was ocurring especially since I had no problems with this before. After doing the various checks on the hoses and seeing if the thermoswitches were functioning, I realized that I had not bled the system as the owners manual had indicated and this forum recommends. In addition, in the owners manual section on "cooling system", the manual had indicated to turn the ignition key to the "on" position and turning the temperature control to full hot (of course this was for draining the system but it made sense to ensure that I was able to fill up the system to its capacity and purge any air that was there as well). It turned out that I did have air in the system and I was able to pour almost another gallon of coolant. After running it at idle for over 15 minutes the temperature gauge does not move past slightly below the half way point and I was also able to hear the fans kick on after about 12 minutes then off again. I was sure that I was going to have to replace sensors and thermostats just to make it work again. Troubleshooting does pay dividends. Thanks again!