TGIF All,

The other night while sitting at idle for about 10 minutes in my 97 Accord SE, the engine coolant got pretty hot on the instrument panel, almost up to the red mark.

As soon as I started driving, the temperature came right down.

I checked the coolant level today, which is fine.

Can someone give a brief explanation of the proper operation of the 2 coolant fans, as to whether they should both come on when the engine is running or if it is based on temperature?

I did start the engine and put the AC on and both fans did run at that time.

Thanks!

 

Fans should come on when coolant reaches about 195F if AC is not on. Thermoswitch A (near thermostat housing) which controls fans w/o AC is likely stuck open preventing the fans from ever engaging w/o AC commanded.

You can confirm, switch is open by jumping the two harness side connector pins to the thermoswitch A. If fans come on when keyswitch is turned to On, then switch is open. This confirms that wiring or connector fault is not the problem.

However, thermoswitch A supposed to be open at any temp < 195F, so only a boiling water test can confirm the switch fails to close when temp reaches 195F.

good luck

 

Thanks TH for the information, I'll try the connector pin test to start with.

One thing I noticed recently, in the past whenever I would shut the engine off hot I would always hear one of the cooling fans come on for a few seconds and then shut off. I do not hear this now when shutting the engine off.

 

A second thermoswitch B (near upper radiator hose fitting on engine) controls fan operation when engine is OFF.

If coolant temp > 223F w/ engine OFF, thermoswitch B closes and radiator fan should run for 15 mins and cut off. This provides cooling to prevent excessive heat soak temps in cylinder head which can damage head gasket.

good luck

 

Well I did the connector test for the switch on the thermostat housing, and the cooling fan started when jumped out. Today I went to autozone and replaced the switch-A.

However I ran the engine for several minutes, and using my digital temperature meter had 210 degrees coming out of the engine, but no fans ever started. When I shut the engine down the fan on the left side (looking front to back) always comes on, but I never see the other fan come on.

Thought for sure it was the switch, but not sure what to do at this point.

Any suggestions????

 

If only one fan came on w/ jumper test, then that fan or fan relay are likely faults.

It is surprising that cooling fans did not come on w/ IR temp gauge showing 210F. What did car temp gauge show at this point?

I have found in past that it can take a long time to get fans to run w/o AC on or driving.

Suggest checking calibration of your IR gauge w/ ice and boiling water.

good luck

 

How did you check the coolant level? Did you look at the plastic overflow bottle, or did you remove the radiator cap to make sure the radiator is filled?

When the key is in the II position, jumping the Temp Switch A electrical connector should turn on both fans.

When the car is turned off, jumping Temp Switch B will turn on the passenger side fan (called radiator fan).

If only one fan turns on when you jump Temp Switch A, then there is a problem with the fan that did not turn on.

 

TH/PA,

Thanks so much for the valuable information. I had my temperature switches mixed up, thinking the thermostat housing switch A was the switch near the front where the coolant returns to the top of the radiator, which is actually B switch.

I jumped switch A connector (rear vertical mounted switch) and both fans started.
I also jumped switch B connector (front horizontal) and the left or radiator fan started.

So I realized I bought A switch, but mounted it in the front where B switch is.

After making the swap and re-installing the original B switch, and replacing A switch both coolant fans started when the engine heated up, so I think I am good to go now.

Funny how both switches are exactly the same size and style, I guess the only difference might be the temperature setting.

Anyway hope you both had a good weekend and thanks again!

 

Thanks for followup on problem.

good luck