Cooling fans not turning on?

Tiny
CMARLEY
  • MEMBER
  • 2006 VOLKSWAGEN JETTA
  • 2.5L
  • 5 CYL
  • 2WD
  • AUTOMATIC
  • 205,270 MILES
I changed the water pump, radiator, cooling fans, thermostat, temperature sensors, and heater blower. Checked fuses, none blown. Please help.
Friday, March 28th, 2025 AT 1:54 PM

5 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 54,144 POSTS
Do the fans come on when the A/C is switched on? We can tell if the fan has a bad ground by checking the power when the AC system is on. Please test the red wire, also, see if there is power to the fuse #3 in the fuse panel under the hood. Also, check the ground which is the brown wire, this guide will show you how:

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

The ground G642 is at the left side of the engine compartment. Make sure to disconnect the fans before testing. Let me know what you find.
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Saturday, March 29th, 2025 AT 11:25 AM
Tiny
CMARLEY
  • MEMBER
  • 3 POSTS
I apologize for needing clarification. Test the fans when the A/C is running? If they don't come on, unplug them and then test
the red wire on the fans, correct?
Then test fuse # 3 under the hood and the ground.
Report back to you.
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Saturday, March 29th, 2025 AT 4:05 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 54,144 POSTS
Yes, start the engine and turn the A/C on to see if the fans are coming on. If not check fuse #3 and if that is okay see if there is power to the red wire and if so, check the ground and it's okay the fan motor module is bad.
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Monday, March 31st, 2025 AT 11:06 AM
Tiny
CMARLEY
  • MEMBER
  • 3 POSTS
Fans didn't come on when turned on AC. Changed out fuse 3 then they came on. Was driving when I lost AC, Heat & Fans. Switched out relay
and they came back on. But still boiling out of overflow tank.
In the wire diagrams I have seen, it usually shows (2) 100 (white) relays. But my car had a 100 (white) relay & a 465 (gray) relay. So when I said switched out relay, I switched their positions.
Do I need 2 - 100(white) relays?
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Tuesday, April 1st, 2025 AT 11:46 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 54,144 POSTS
So the fans are working while the engine is overheating? If so, the cooling fans are not the problem, you may have a stuck thermostat, or the engine has a blown head gasket. Please go over these two guides to help confirm the issues:

https://www.2carpros.com/articles/engine-overheating-or-running-hot

and

https://www.2carpros.com/articles/head-gasket-blown-test

Please go over these guides and get back to us.
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Wednesday, April 2nd, 2025 AT 10:44 AM

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