Honda Civic 8th Gen fans not turning on

hammi (hammi) 2021-10-05 02:14:46 +0500 #1

Recently bought a civic 8th gen and the radiator fans were running direct. I disconnected the direct circuit but the fans wont turn on. On the computer if I do a Radiator fan test they do turn on.
ECT sensor 1 goes up to 107 degrees and the heat bars go up on the cluster ECT sensor 2 stays at around 90 degrees.
Which sensors engages the fans or what can be the cause?
Thank you

hammi (hammi) 2021-10-05 02:19:10 +0500 #2

@Xulfiqar @Hassan1991

Hassan1991 (Electrical Engineer ) 2021-10-05 02:50:21 +0500 #3

Does the condenser fan turns on when you switch ac on?
Radiator fan should turn on after 96C if either of ECT reads it. Without AC.
Check the thermostat. There's too much temperature difference or ECT 2 is bad.
Both ECT's are connected to ecu. So it reads both.

hammi (hammi) 2021-10-05 10:06:09 +0500 #4

Yes If I turn on the AC both fans turn on

hammi (hammi) 2021-10-05 10:10:28 +0500 #5

With fans running direct the car does not heat up. I dont think the thermostat is faulty. If it takes the reading from either of the sensors then the fan should run as temp on ECT1 goes up to 110

Hassan1991 (Electrical Engineer ) 2021-10-05 14:01:51 +0500 #6

Yes, but there should not be that much temperature difference. ECT 2 doesn't go about 90 at all?

hammi (hammi) 2021-10-05 16:51:28 +0500 #7

When ECT1 is at around 105ish ECT is around 80-85. The engine is already heating up hence I did not wait to check if ECT2 goes 90+ as ECT1 will touch the ceiling by then and so will my the engine head

hammi (hammi) 2021-10-05 16:53:26 +0500 #8

I think there are air pockets in the cooling system will refill and check else the sensor is faulty or the thermo is stuck. Serviced the radiator but no luck

Hassan1991 (Electrical Engineer ) 2021-10-05 17:14:45 +0500 #9

Haha good you didn't wait.
Actually lower ect will read low. Because it's reading the coolant being cool down by radiator.
Not sure how much temperature should it be nominal. Between it means radiator is doing the job.
Ecu should turn the fan on already.
Does only radiator fan doesn't get on without ac?
FANL turns on the radiator fan at 96 C.
There's 3 relay in total AC condenser fan relay, Radiator fan relay and Fan control relay.
Check radiator fan relay.

hammi (hammi) 2021-10-05 17:26:06 +0500 #10

I think the relays are fine. If I do the manual fan actuation test with the scanner the fans turn on. Its the ECT2 sensor that needs to be fixed. Checked another civic the difference between the 2 sensors was hardly 5 degrees.

Hassan1991 (Electrical Engineer ) 2021-10-05 19:18:53 +0500 #11

Fan control relay turns both fan in together. Radiator fan relay only turns on One.
You can do bench test of ECT.
Let me share the diagram.

hammi (hammi) 2021-10-06 01:33:01 +0500 #12

Used a funnel to burp out air from the cooling system. Everything back to normal now. Now I have another error from the ABS system something like “front right and rear left tyre wrong tyre size”
Front wheels speed and rear wheels speed is different on the scanner. Almost 5-6kmph difference. Front wheels speed is same as car speed. Could be after market chinese hub?

Hassan1991 (Electrical Engineer ) 2021-10-06 01:46:00 +0500 #13

Great.
What is the difference in temperature now?
Tyre sizes are same?
Yes if hubs got more teeth's then ecu will read more speed.

hammi (hammi) 2021-10-06 21:08:28 +0500 #14

ECT2 is around 95-96 and fans turn on ECT1 is around 100-101 that time.
Tyre size is same. Changed the rear hubs lets see. Can be a worn out teeth or something

zain73 (Zayn Javed) 2024-01-06 23:13:48 +0500 #15

Salam Brother
Which Device have you used to read both ect 1 and 2 separately ?

Hassan1991 (Electrical Engineer ) 2024-01-07 02:40:20 +0500 #16