Thanks for your help. This radiator fan switch for my car costs at the Autozone store about $27 plus tax. It is is Duralast brand and said it is life time warranty. I guess this is better deal plus I can match my old part and get it immediately, too. Do you think this is right part for my car?

 

It should have switch temp stamped on body somewhere (93C or 199F).

good luck

 

Thank you again. Yesterday, I did one more test. I cleaned dirt around both switches and ECT sensors (Without removing them). Then, I bled coolant from the system to remove any possibility of air pocket locked in there. Then I started the engine for 20 minutes idling and pressing a little gas to heat up. Surprizingly, the temperature gauge never went up above normal (below midpoint), but radiator fan also did not get turned on.
Does this mean, the thermo switch A is working back again or still it is bad because radiator fan did not get turned on? Or maybe the outside temperature was a little cooler than the other day. So, maybe I have to test it on hot day to be consistent?

 

It's a good result for your overall cooling system. It means that your radiator was able to keep cool even without the fan.

But you didn't get hot enough to test that fan switch.

On a cooler day, I normally have to block the radiator (cardboard, blanket) otherwise it never gets hot enough for the fan to come on. The fan would normally not come on until it gets noticably above "normal". Maybe 65% on the gauge, but certainly not all the way up to the red.

If you test it again, be prepared to turn on the heater all the way to HOT & blast the ventilation fan. Just in case the radiator fan doesn't come on.

 

Hi JimBlake, Thanks for help.

1) My "normal" temperature gauge is about 35%. I was told that I should not let it go above 50% to keep it safe. By allowing it to go up to 65% gauge temperature, will my head gasket get more damage each time I do this?

Actually, as I mentioned in my first message, accidentally, my temperature gauge went up to almost to red mark while I was driving stop and go looking for parking space on a very hot day (was not paying attention to my gauge earlier). But I did not check under the hood to see if radiator fan working, but rather I put the AC on to bring down the temperature and it came down to normal slowly.

2) What is the reason for testing with the heater on HOT & full blast ventilation to prevent the radiator fan turned on? We do want radiator fan to come on which shows it is working, right?

 

Today I tested my thermo radiator fan switch A. The heater was all the way HOT and full blast ventilation. The outside temperature was over 100 F. Prior to idling, I drove around for half an hour and stopped my car in my garage idling. At about 16 minutes past around 60 % temperature gauge, the radiator fan and condensor fan both came on and lasted for about 2 min. Actually, i blocked radiator with blanket for short while. And prior to fans coming on, my temperature gauge had slightly decline down toward midpoint. Then only both radiator fan and condensor fan came on.

I guess this time something to do with bleeding coolant system and cleaning ECT sensors might have worked out for my thermo fan switch A. But after turning the engine off, my condensor fan did not come on which is controlled by thermo switch B. (is this normal?)

My 2nd question is that is it normal for temperature gauge to reach 60% (above midpoint) to make radiator fan and condensor fan come on?

Thank you.

 

The normal range for the temperature gauge is around 35%.

The radiator fan will turn on when the engine is off if thermoswitch B is closed.

Jim has a nice writeup about the sensors in the common DIY thread on top of the gen tech help forum.

Here is my way of explaining them.

Your accord has four sensors for coolant temperature.

1&2 are the thermo-switches A and B. They are on/off (closed/open) switches that turn on the radiator fans. A closes at 200F. B closes at 223F.

3&4 are the engine coolant temperature sensor (ECT) and the engine coolant temperature sending unit. These two are more like thermometers that send the temperature as a signal (resistance changes with temperature). The ECT sends the temperature to the engine computer. The gauge sending unit sends the temperature to the gauge you see inside your car.

All four sensors are independent of each other. The engine computer only sees the signal from the ECT, the gauge only sees the signal from the sending unit, etc...

What may be happening is that your gauge in the car or the sending unit are not working properly. You wouldn't see the proper temperature inside the car, even though all is fine.

There are a couple of ways to test.

1. Read the temperature of the engine using an IR gun when the fans turn on when the engine is running. My $10 craftsman volt meter had a setting to read temperature.

2. Unplug the sending unit and measure the resistance when the fans turn on. You will need a volt meter to do this. Touch one meter lead to the tip of the sending unit. Touch the other lead to ground (valve cover bolt). The resistance should be 32-49 ohms.

 

Thank you for more information. I have to get IR gun to measure temperature. Is it easy to remove ECT sending unit sensor to test its resistance?

So, my thermoswitch A is definitely in working condition, right? (because my radiator fan came on after reaching temperature gauge around 60%)

You said that the normal range for the temperature gauge was around 35%. My question is that what is normal temperature gauge range when the radiator fan comes on hot engine? Is it always above midpoint ( more than 50%)?

Thank you.

 

Could possibly be the Rad. fan box under glove box, My fans wouldnt come on regardless of A/C on or not, turns out the box under glove box almost set on fire for some reason

 

I've been REAL busy for a few weeks so haven't been here.

You asked why you should turn on the heat? I said to BE PREPARED to turn it on, only if the fan switch is broken and the fan never comes on. Running the heater is a real good way to cool it down quickly. Switching on the AC also works, IF both fans come one correctly with the AC.