Cooling fans do not appear to be working correctly

Tiny
JESSEPATTY
  • MEMBER
  • 2004 BUICK RENDEZVOUS
  • 3.4L
  • 6 CYL
  • FWD
  • AUTOMATIC
Cooling fans on my wife's Buick appear to be coming on to late and to slow to keep the car's temp down in heavy traffic.

Car ran quite hot last Friday (221* on my scanner) in heavy traffic tripping the SES/MIL light. I pulled codes and found a P0128 so I changed the coolant temp sensor and cleared codes.

Drove it for while with no MIL light and it ran right at 201* the entire drive. I came home and let it idle and in about 5 minutes is was right back up to 224* at which time the fans came on at a very slow speed. They ran for 5 minutes dropping it to 217* when they shut off. I decided to go ahead and replace the serp belt due to cracks when I noticed some bearing play in the water pump so I replaced the water pump. Purged the system of air and let it idle. Within 5 mins it was right back up to 224* at which time the fans came on at a slow speed again.

I feel the fans are coming on way to late and at too slow a speed to be effective. If I understand correctly, this vehicle has 2-speed fans, if this is true, High speed is not working. I'll also point out that when the AC is on both fans run continuously at slow speed.

I've checked the two cooling fan fuses and they are good, I also checked three cooling fan relays by swapping them around and it made no difference so I think all the relays are working but I am not 100% sure.

Car does not run over 199-200* when the AC remains on and/or at night when it's cool out. It's only doing it during low airflow through the radiator periods above 80*.

If you could shed some light on this issue I sure would appreciate it.

Thanks
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Sunday, February 23rd, 2014 AT 9:39 PM

4 Replies

Tiny
HMAC300
  • EXPERT
Actually 221 isn't to bad a temp to worry about but check the connections on the pcm they may be corroded etc and the ground. When a/c is on is when other fan kicks on always. It can be either of these. Also withengine off and fans disconnected feel for cold spots on radiator if there are then the rad is bad it should be about same temp all over.
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Monday, February 24th, 2014 AT 7:15 AM
Tiny
JESSEPATTY
  • MEMBER
Thank you.

I understand 221 isn't terrible but once it gets there it tends to keep climbing in stop and go traffic. I have her car today to figure it out and earlier I took a 30 minutes ride and as long as I was moving it stayed right around 199-202 on my scanner. As soon as I stopped for a light or something it began to climb quickly.

I've changed the Coolant temp sensor, radiator cap, Serp belt and water pump thus far. I'm going to go change the thermostat now and see what that does. I was trying to put that off because so much has to come off to replace it

Thank you, I appreciate the input.
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Monday, February 24th, 2014 AT 10:04 AM
Tiny
KEN
  • ADMIN
It sounds like the PCM is not triggering the high speed relay can you use a test light to see if a trigger signal is being sent when the engine is hot? Use the wiring diagram about and this guide.

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

Please run this test and get back to us so we can continue helping you.

Best, Ken
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Thursday, March 2nd, 2017 AT 11:30 AM
Tiny
KEN
  • ADMIN
Hey,

Did you ever get the problem fixed?

Best, Ken
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Thursday, March 2nd, 2017 AT 11:30 AM

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