Cooling fan not working properly

MUSICGENIUS83

MEMBER
1998 HONDA ACCORD
2.3L
4 CYL
270,000 MILES

At some point my fans stopped coming on cool off the engine they only come on when I have the air conditioning on normally the fans pop on and off every couple minutes. Even at idle to cool off the engine when the A/C is off. I have a new thermostat and a new radiator and I drained and refilled the coolant with new coolant. I had replaced the fan sensor I believe it's called the thermal fan switch or sensor with no luck. So I've ordered a coolant temperature sensor hoping because those two sensors work together that may be the coolant temperature sensor isn't sending the right signal to the fan sensor. I just wanted to know if I'm in the right area of what I'm doing. I took it on the freeway and drove it around a few blocks purposely trying to get it hot and the fans won't come on even when it's hot and at temperature.

6 Replies

DANNY L

MECHANIC
5,648 POSTS

Hello, I'm Danny.

Yes, you are looking into the correct problem area. I would suggest replacing the coolant temperature sensor. One fan will always run continually when the air conditioning is turn on.You have just lost the function when engine is running hot.Here is a basic tutorial showing what is involved:

https://www.2carpros.com/articles/coolant-temperature-sensor-cts-replacement

I've attached a picture below of its location on your car.Just be careful when replacing as to be prepared to lose a bit of coolant when removed.Hope this helps and thanks for using 2carPros.

Image (Click to make bigger)

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Friday, July 3rd, 2020 AT 10:02 PM

MUSICGENIUS83

MEMBER
29 POSTS

Okay, so I replaced a coolant temperature sensor. I also replace the one right next to it called the sending unit just in case there was anything wrong with that. So now it has a new sending unit, a new coolant temperature sensor and a new fan switch. I drove it the same way today with the A/C on flying up and down hills trying to get it hot enough for the fan to come on and the fan never came on unless the A/C is on. I know the thermostat is working because the warm coolant is going through the top and the bottom hose, so I know it's circulating through and the thermostat is letting it through. I'm just not sure where to go from here. The temperature needle has never gone over halfway the car hasn't overheated. I'm just worried that driving a car in the heat and getting hot. The fact that the fans don't come on will eventually cause it to overheat. I sat at idle for 20 minutes before I took the car out and then when I got back I sat for another 15 minutes and they never came on, but my engine is scalding hot. Both the radiator hoses are hot as fire and I just can't understand why the fans wont come on.

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Monday, July 6th, 2020 AT 3:04 PM

DANNY L

MECHANIC
5,648 POSTS

Hello again.

Quick question. Where was temperature needle reading on the dash during all this time? Did it show any signs of overheating during all this? Let me know.

Danny-

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Tuesday, July 7th, 2020 AT 8:18 AM

MUSICGENIUS83

MEMBER
29 POSTS

Hello, no, needle never got hot stayed little under halfway point, fans finally kicked on, had to let it idle for 20 minutes, then took it on freeway for 15 minutes. Got back home they finally started working, guess just took time. Been working on it for about 3 weeks hasn't been driven it a bit. Thanks for your help I appreciate it.

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Tuesday, July 7th, 2020 AT 8:32 PM

STEVE W.

MECHANIC
12,968 POSTS

Most fans do not turn on until the coolant gets into the 200 degree range. So the hoses are going to be very hot. However a common issue for this is after coolant was drained and parts were changed or there is any leakage and the coolant gets low, an air pocket can get trapped around the sensors and now the sensor thinks everything is fine because the air doesn't transfer the heat like the coolant does.