This has been an ongoing issue that at first, appeared to be corrected after I replaced the rear thermoswitch. The car is a 97 accord dx.

Here is a link to my original issue that was solved back in January:
https://www.hondaaccordforum.com/for...ot-come-44885/

This corrected the problem until recently. About a month ago I noticed the exact same symptoms - fan not turning on when temperature started climbing at red lights (while driving the temperate remains in a safe range). Typically the fan turns on when the temp gauge reads just over 1/2. As a result, the temperature falls to about 3/8 and the fan shuts off. Well, just like this past winter, my fan was not kicking on anymore. Jumping the thermoswitch connector turns the fan on instantly. With this in mind, I decided to replace the thermoswitch again.

Replacing the switch again worked and I initially thought maybe it was a short lived replacement part the first time. However, not even two weeks later, the overheating issue started popping up again and the fan does not turn on. It seems to have gradually gotten worse. At first, the fan turned on just past 1/2 on the heat gauge. Then, about 5 days later, the fan wasn't turning on until about 3/4 (which seems way too high). Now, it just doesn't turn on at all. However, Jumping the fan always turns it on.

Now, I suppose I could replace the thermoswitch again, but it just seems VERY unlikely that the same part would be faulty twice. Could the fan control module need replacing? It seems unlikely since, unless I'm mistaken, jumping the fan successfully would indicate that the fan control module is operating properly.

Both replacement thermoswitches were the same brand from autozone. Should I attempt using a different manufacturers part?

Here is a link to the thermoswitch that I have used twice now.
Duralast/Cooling Fan Switch - Radiator (TU197) | AutoZone.com

Has anyone ever experienced a similar issue? I'm just about out of ideas.

 

Are you getting air into the cooling system? If there is air in the system the switch will not read the temp properly and thus not turn on the fans.

Now if there is air in the system.....then next question is why?

 

As far as I know there is no air getting into the cooling system. The radiator fan functions properly when the car shuts off while its hot - fan instantly comes on which indicates to me that at least the lower thermoswitch is able to read the correct temperature.

 

Check for air in the system, please.

Was the thermostat replaced back in January?

 

I'll bleed the system tonight and see how that goes.

Yes, the thermostat was also replaced back in January. At that time, I replaced the thermostat before the replacing the thermoswitch. It did not correct my fan issue. Each time I have installed a new thermoswitch (three times now), the radiator cooling fan has worked properly. The first time it worked for a number of months. Replacing it a second time about a month, and the third time just about 10 days.

 

It could be the switch has gone bad again, just hard to understand how three have gone bad......me, if you think it has gone bad and don't want to buy a new Honda OEM switch, swing thru a junk yard and grab one for $5~$10 and see what you get from there.

 

I still plan on bleeding the cooling system, but probably won't get to that until tomorrow at this point. The car is hot right now and it'll be dark before I can do it.

Anyway, I took a look at the fuse and noticed that it has a very dark spot on the right side of it. The wire is still intact but part of it appears burned to me. I've attached a picture of it. Does this look not right to anyone else?

Just to test, I swapped the fuse with another fuse and the fan came right on once it got up to temp. Climbed just about 1/2 and clicked on.

I'm still inclined to think that there is an underlying issue if this fuse is not good.

 

I'm a volt meter or test light person......means I'm blind as a bat. Fueses are cheap....put a new one in and go from there.

 

Well thanks for the recommendation on bleeding the system. There was definitely some air in there, but the bigger surprise was the coolant reservoir was bone dry. It was filled up to an acceptable line the week prior after the thermoswitch was changed. I have not noticed any leaks under my car since replacing the switch.

After bleeding the system and replenishing the reservoir last night the radiator fan operated completely normal and was actually turning on sooner than I had been accustomed to. I suppose there previously wasn't enough coolant in the system for the sensor to get an accurate temperature.

Driving in to train station this morning I was anxious to see if my fans would come on. I never got the chance to test the fan because my temp didn't rise enough by the time I got in. I sat in the car and let it idle for about a minute and noticed a small amount of smoke coming from the hood. I thought this was strange since my temperature gauge was reading under 1/2. I then remembered that some coolant had overflowed the previous day when I bled the system and I definitely did not do a great job cleaning all of it off. I decided to quickly pop the hood and noticed that the smoke being generated was coming from the residue that I never fully cleaned up.

I then decided to check the reservoir. After unscrewing the cap I immediately noticed white smoke in the reservoir, as if it had been boiling, and the tank almost completely dry again. I didn't have any more time to look at anything because my train was leaving in a couple of minutes.

There must be a leak somewhere, but I have no puddles forming under my car when I park. At this point I'm not sure where to begin.

 

May be an internal leak. How are cold starts?