Overheating Help! | Testing Cooling Fans - Relays - Connections


If your vehicle is overheating due to a non-working cooling fan motor, this video will show the steps involved in diagnosing the problem. Cooling fan motor testing (low and high speeds), relays, harness connectors...it's all here.

Generally, the low speed fan kicks on when the A/C is turned on or when the coolant temperature hits around 200 degrees F. High speed kicks on around 220F.

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Tools Used:

Safety Glasses

Digital Multi-Meter


This video is being performed by an experienced tech. Any attempt to repair automotive parts and/or systems carries risk of ...

Channel:  CarsNToys

maybe ggod explane if the sound was here


You just earned yourself a subscriber!

David Palmer 

It is true, the coolant temperature sensor activates the cooling fans, when the resistance drops from 38,000 ohms resistance, at 20 degrees celsius, to 1800 ohms, at 90 degrees celsius, this is when the fans will be deactivated.


thank you. that was helpful.

Danish Zaidi 

I have a corolla with radiator fan issue, the fan works directly, relays are fine too, im gonna check continuity of the fan wiring tomorrow, fingers crossed.

Hamish Jennings 

mate full thumbs up great video ..that troubles shoot's most front wheel drive car fan fault's if all with electric fans great work . cheers

Muhammed Zahid 

Would that be identified through a obd test?

Jesus Val3ncia 

Can somebody help please!!. I have a 2009 Chevrolet silverado with the 5.3 engine . it overheats beacuse the fans dont want to turn on automatically. This just started a week ago . fans only turn on when i turn the ac and only stay on the low speed. I change the thermostat. Drains the coolant and put in fresh coolant , temp sensor is in working conditiin, relays are good and also fuses.i alsp check all the voltage and gound for everything. Please help. Im going nuts!.

Amal Joseph 

Do all cars starts its fan when AC turned on .... i got only one high speed fan near radiator. i got chevy aveo 2009

Hilario Rodriguez 

at 3:50, if you don't have power, you have an open circuit.  A short would drain your battery and most likely start a fire.

Creation World 

Very good and clear , thanks mate

Tolin Pie 

Thank you ......you did a great job explaining in details ...You are the best.....

Leon Peterson 

I notice the engine cover says V6 but it looks like an inline 6 cylinder.......


Nice video i ve got electrical condenser fan not working really is ok fan is ok tested fuse is ok

There is no voltage to terminal 30 and 87

Also continuouty for negative between fan connector and relay 87 is not there once you attach probe no sound for continuouty only the 1 sign on voltmeter vanished dissapeared but for 30 which is positive there is contiuty so i have 2 issue 😫 really big headache to dig in these wiring on and find breaks in harness in a daily used car 😓

Thomas Dinh 

I love your video ! You are explaining very clearly every steps all the ways . I am admired you ! You are just as good like “ Christ fix guy “ . You are a good young man . Thank you for the video !!! 👍👌👏

Abhishek Sidhu 

Very nicely described and very clean video... good job bro... very helpful. Cheers!!


Beautiful Man! I've been a mech for 35 years and you dumbed this down to where a high school student could understand it. Good job.

Verum Dicere 

My Nissan Versa SV doesn't have this setup. I see fuses with tons of colorful wires attached. Should I pull out the fuse box from the engine I cannot access to see of the Relays are in there?

Tiago Rosa 

Very very good your vídeo!

Do you have another video like thia, but for the C4 Citroen 1.6 2013?

I live in Brazil!

Danielle Furry 

all of that is helpful but missed one part way in the back there the thermostat housing is a switching unit " coolant temperature sensor " if this is not functioning it doesn't send the " click on " signal to the relays and thus fans don't run this can be caused by electronic failure or the thermostat itself is not opening to allow the coolant thru the pipe to the sensor as u showed with this video all the easy to reach stuff was tested and working so for non working fan under these test cases relays / wireing / fan moters done would inverably be the CTS switch or a blocked thermostat port

Dion Jayasekara 

super video thanks

zia walizada 

i have golf 7 automatic transmission when i drive it for few minutes when i park the car but cooling fan still running for few minutes and make noise any suggestion

Obika Daniel 

what is the work of the grey relay just beside the fan 3, and how to test if that relay is working fine? thanks

I like your video

Jon Bongo 

I have a 1999 Dodge not working at all with or without the air. Could be be the temperature control sensor that runs the fans ?

dubsaloon Moore 

I believe the "wifi" icon indicates audible. Very nice video. Thank you.

Ricky Harris 

I have a 2006 Pontiac Grand Prix 3.8lt w/ supercharger. I tried everything here and it all checks out. But I have replaced all the relays, wire plugs, coolant temp sensor, thermostat, entire fan assembly and the PCM. When the car is cool the fans blow and work great, after driving it and the engine gets warmed up the driver side fan doesn't work. Any suggestions please, thanks in advance.

Kiraro The Kitsune 

This video has a ChrisFix amount of detail, straight to the point. I like it

Zulkefli Jamil 

Thank you boss..

gus ponce 

Thanks for that info!

jay man 

What if one works and the other doesn't

rr po 

Great video. I have a fan problem, they are not going on high and I am getting no voltage to the drivers side fan on a nissan quest 2007. I checked the relay and the relay works. So check the voltage at the relay plug and I am getting only one 12 volt reading at pin 2. So now I am testing 12 volts on the other pins for that same plug and I am not getting 12 volts on any other pin. I don't know where to go next. It will be greatly appreciated if you can give me a bit of direction. Thanks for your time and help.

Muhib Uddin 

Both speed in high and low speed fan works when tried out with a diagnostic machine.I replaced my relays resistor, this fixed my low speed fan however it doesnt turn on my high speed fan. What could the issue be?

Israel Travieso 

Hey guy I have changed everything possible to stop overheating Saturn sc2.   Changed sensor, water pump ,thermo, etc. At first it wouldn't  overheat when the sensor was unplugged but now it does regardless. I flushed the engine and poured some head gasket sealer and nothing. I remember it all started after heater core flush, but don't understand relationship if any. Even changed the pcu, lucky I bought it cheap.   It was suggested that it may be the heater core, but like I said it was flushed and there are no leaks.   HELP. I questioned several  so called mechanics on the net but no answer.

It _your_boy_Johnny B 

When I turn my AC on both my fan comes on but doesn’t work when the engine is hot so the car Will overheat

Timothy Serrano 

What if you ac not working. The fan going to work?

Mohammad Saleem 

My mini pajer heating but why

Andrew Wu 

Thank you for your very helpful vid. I was able to fixed my overheating problem today! Your vid is straight forward and to the point! Kudos bro!


Can a radiator fan motor blow fuses

Flavio Sanchez 

Wow I thought it would be way hard, good job


Very helpful indeed. You are passing along some great information in an easy to understand, well filmed format. Time for me to start probing my Jeep and see what's what.

You earned another sub and the big ole thumbs up.

Thank you.

D.j. B 

I need instructions so on how to test the relays that are in my 03 focus cooling fans

D.j. B 

I Have a 03 focus with zetec motor.my cooling fans are not working! I ran power(using a 15 amp fuse) to each individual fan & they worked! I replaced the head temp sensor & cooling fan solonoid. I replaced the relays, & still my fans don't work! Then, I smoked my multimeter, accidentally used the unfused side on a battery! I need a new one asap!!!!


Good job!!!

Priya M 



kenneth lazo 

i have a toyota hiace grandia gl.

my cooling fan or rad fan when I switch ON the AC the cooling fan/rad fan will turn ON then after a minute the rad fan will turn off automatically then it will turn ON after a seconds (5-10s) ..

why rad fan do that??

i thought when I switch ON the AC will turn On at low speed then when it gets hot the rad fan will switch to hi-speed.. but my van its not doing the way.. how to fix it?

Oilicec Otos 

I have a 2013 Nissan NV200 and the radiator fans will not shut off. They drained my battery last night. Any help?

rocketman ure 

👍very helpful thanks a lot everything nice and clear

Chevy sucks 

Bro my fans kick on with the ac on only what would you check for

Mark Harris 

Whether or not I can test my secondary fan on my 1982 MBZ 300TD this way, or not, I still appreciated this well done explanation.

matt brown 

Great video! Used this to fix my radiator fan assembly in a 2004 Murano. Thanks!!!