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Radiator Fan Not Working!


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#1
oz6261993

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Hi guys,


1. Turn key to "ON" ( Engine not Running )
2. Unplug the coolant temp sensor
3. Result = Cooling Fan turn on or running ( when i unplug the coolant temp sensor )

My prob is when the engine is hot the cooling fan doens't come on...last time i nearly had a major OVERHEAT.
So can someone pls tell me what is wrong with my car????

Cheers :smile:

#2
jpit

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You have to have the car running.

1)Start your car
2)Disconnect the coolant temp sensor (CTS)
3)After about 10 seconds the driverside fan will come on

If the fan doesn't cycle on you have to figure out whether it's a bad CTS, a bad fan or fan relay. If you disconnect the connector leading to the fan you can apply 12volts to one contact and ground to the other and the fan will spin. There may be a diode inside so if it doesn't spin right a way swap the 12v and ground leads and check again.

The CTS is also sensed by the ECU but it generally takes a shorted one to make it fail. One that is 'open' would cause the fan to run all the time.

More apt to be just a bad connection at the fan connector. Clean the contacts with a nail file. Also check the 40amp cooling fan fuse located in the engine compartment fuse block.

#3
oz6261993

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Ok i started the car.....unplug the CTS....the cooling fan kick in.
So is that mean there is nothing wrong with my cooling fan???

My problem is that when the engine is at running HOT, the fan won't kick in....that's what cause my engine to OVERHEAT last time....luckily i was able to save it on time!


Cheers :smile:

#4
jpit

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There's definitely nothing wrong with your cooling fan, cooling fan relays or the fuse.

*Revised by jpit* - It could be a fan relay or the fan motor still since your '93 model has a 2-speed fan. You can verify the fan motor by disconnecting the the 4-pin connector from the fan and attaching the fan's Black lead to ground and 12volts to any of the other terminals, Blue/yellow or Blue/Black and you will have high or low speed operation depending on the terminal you connect 12v to.

Possible problem with the CTS but highly unlikely. You can check it with a meter. The hotter it gets the lower the resistance. Colder the CTS gets the higher the resistance. You'll most likely spend all that time measuring it to find out it's fine. The good news is that they are inexpensive, generally less than $20.

I would check and make sure your coolant level is topped off in your radiator and in your overflow reservoir. 50/50 mixture is preferred.

You may have a sticking thermostat. If it sticks in the closed position it can stop the flow of coolant and if no coolant can flow then the CTS may not sense the hotter water. Just a thought.

Are you positive that you are overheating? You could have a guage or temperature sender problem that's falsely signalling a problem.

#5
Trebuchet03

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Not sure if the 93 models are the same... but my 97 has two sensor - 1 for the gauge and 1 for the ECU - it could be possible the gauge CTS has failed (again, unlikely) or there is air in the system causing a false reading...

#6
oz6261993

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Yes it OVERHEAT before luckily there is no MAJOR DAMAGE to my engine!
I still don't understand why the fan still won't kick in after a 30 mins drive, reason being its Spring in Australia now and driving around for 30 mins will definely activate the fan to kick in.

#7
Trebuchet03

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if you are just driving around, the fan won't necessarily need to kick on... Driving around pushes air across the radiator - when you are standing still, there is no airflow and it becomes necessary for the fan to be on...

When you turn on your air conditioning, do both of the fans on the radiator turn on?

#8
oz6261993

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Yeah i try that also....i park the car and let it idle for 30 mins and nothing had happend!
When i try on the A/C on only 1 fan work ( the biigest of the 2 work)
I had check the FUSE under the steering wheel and under the bonnet near the battery!

#9
Trebuchet03

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which side of the engine bay is it on? Left or right (from the perspective of the driver sitting in the car)...


Its possible that the relay that controls that fan is dead

#10
oz6261993

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Well from the perspective of the driver sitting in the car when i turn on the A/C only the larger fan works.
The larger fan is located at the left hand of the passenger's sit, where as the smaller fan are located at the driver's sit.
Anway how do you test for the relay for malfunction???

#11
jpit

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Your engine cooling fan is fine since you already proved that by disconnecting the CTS and it came on. There is nothing wrong with the fan/fan motor itself. It's a very simple device. You apply 12volts to it and it spins. No 12 volts and it doesn't spin. :smile:

Like trebuchet03 says, the fan doesn't come on very often. I can't remember exactly but I believe the turn-on temp is 203 degrees F. Since you most likely have a 180 fegree F thermostat then during normal operation you won't see the fan cycle on. When it sits and coolant is only flowing slowly through your system then it has a bigger chance of heating up and eventually turns the fan on. I have to agree with you that if my car sat idle for 30 minutes, the fan would most likely kick on sometime during that period. On the other hand if I drive for 30 minutes it most likely WON'T kick on since the airflow through the radiator keeps the temperature down.

Keep in mind that you have coolant in your radiator and not just water for a reason. Water boils at 212 degrees F and the proper coolant/water mixture of 50/50 increases that boiling temp quite a bit. The fact that the system is pressurized increases the boiling temperature also, so the proper radiator cap has to be used. Make sure you have coolant and not just water in your system.

Are you saying that your temperature guage goes to 'H' when idling for 30 minutes and the fan doesn't kick in? Or are you just saying that after idling for 30 minutes the fan doesn't kick in regardless of the where the guage sits?

Do you have an ohmmeter to check voltages and resistance?

To answer your question about testing relays. You apply 12v and ground to the coil side of the relay and this causes the 2 points to close on the relay. Easiset way to check is to remove the relay and using your own wire leads to apply 12volts from your battery. Use a meter to check the continuity of the points. Should read 0 ohms between the points with 12volts a pllied to the coil side.

#12
oz6261993

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Well here is what happened last time......i was driving the car for 5-10 mins for a short trip....i park the car...and all the sudden the water start leaking out under the bonnet ( i should have check where the leaking is at that time!). I am sure the temp gauge is working properly....because at that time the needle reach the "H" mark.

Anyway where is the relay located under the bonnet??? which one should i take it out and test it???
Radiator Cap??? How can you tell its malfunction????

#13
jpit

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Yes it sounds like you have a true overheating problem. You'll need to find out where the coolant(you said water) is leaking from. If it's at the water pump then you have found your problem. I wouldn't rule out a stuck thermostat. It's cheap/easy to replace so I would try that first if you can't figure out if it was just a boilover or a real leak.

If your overheating problem has become consistent then you could try disconnecting your cts to force your fan on and go for a test drive. If it keeps it cool then you could focus on that again(relays). Your relays should be in your fuse block within the engine compartment. I only have 1 for my 97. You have 3 of them because you have a 2 speed fan motor.




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