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My right fan will not come on by itself or with a/c if I use…

Customer Question
My right fan will...

My right fan will not come on by itself or with a/c if I use the computer I can manually turn them on though

Mechanic's Assistant: Have you checked the Freon level?

Yes it’s good just serviced today

Mechanic's Assistant: What is the model/year of your GM?

2006 Yukon xl Denali

Mechanic's Assistant: Are you fixing your Yukon XL yourself? What have you tried so far?

Yes turning fans on manually with tech 2

Submitted: 10 days ago.Category: GM
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Answered in 2 minutes by:
7/11/2018
GM Mechanic: Mechanic01, ASE Certified Technician replied 10 days ago
Mechanic01
Mechanic01, ASE Certified Technician
Category: GM
Satisfied Customers: 3,336
Experience: Owner at Baltic investments
Verified

Hello my name is ***** ***** welcome to just answers! I will be assisting you with all of your vehicle questions today. Please be aware I do not know your skill level or abilities so I will be asking a lot of questions and in a lot of cases we will respond to each other quite a lot before we find a solution. As far as phone calls are concerned you will receive a system automated call request, that is not me, and they do cost more money, I prefer text but in some cases a phone call is required. If I don’t answer right away or quickly in conversation I am helping another customer or have stepped out for a moment and will respond as soon as I can. Also I am not paid hourly by just answers, I am only paid when you rate me, so if you could please respect my time and knowledge by rating me when we are finished that would be wonderful. If you could please indicate your level of experience and what you are looking to get out of your session today. Ok lets get started!

OK so if you have the tech 2 this should be easy, below are the troubleshooting steps for the fans, let me know if you hit any snags

https://www.dropbox.com/s/nwco78wo9owdrpc/wed3.pdf?dl=0

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Customer reply replied 10 days ago
We’ve done all that everything works manually but when we take computer off get engine up to temp or turn on AC 2nd fan doesn’t come on automatically but we can turn on the second fan w the tech 2 manually
GM Mechanic: Mechanic01, ASE Certified Technician replied 10 days ago

so you followed ALL the troubleshooting steps?

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GM Mechanic: Mechanic01, ASE Certified Technician replied 10 days ago

well you should have found something with that, ill open this back up to another tech that may have different tests

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Customer reply replied 10 days ago
We can’t figure it out we can turn them on manually with tech 2 both work just won’t come on with AC or high engine temperature
Customer reply replied 10 days ago
Hello?
GM Mechanic: Robert Blackwell,
 replied 10 days ago
Robert Blackwell
Category: GM
Satisfied Customers: 72
Experience: ASE Master Technician at Taylor Tire
Verified
Hi my names Robert. I'll be helping you out today. So the engine fan comes on but the ac fan does not?
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Customer reply replied 10 days ago
but I can turn it on from tech 2 so fan works
GM Mechanic: Robert Blackwell,
 replied 10 days ago
Alright let me look at some schematics
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GM Mechanic: Robert Blackwell,
 replied 10 days ago
Is it a 1500
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Customer reply replied 10 days ago
Somebody told me it could have something to do with the ambient temperature sensors that are inside the grill would that have anything to do with that fan not kicking on
Customer reply replied 10 days ago
6.0
GM Mechanic: Robert Blackwell,
 replied 10 days ago
Alright let me look at the schematic and see how it is turned on.
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GM Mechanic: Robert Blackwell,
 replied 10 days ago
Right cooling fan as in passenger side?
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Customer reply replied 10 days ago
That’s correct
GM Mechanic: Robert Blackwell,
 replied 10 days ago
According to the schematic their are three relays controlling both fans which are controlled by ground through the pcm. Relay 2 and 3 both control the right fan. Have you replaced these or swapped with with know good relays yet.
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Customer reply replied 10 days ago
both are brand new
Customer reply replied 10 days ago
All three sorry
GM Mechanic: Robert Blackwell,
 replied 10 days ago
Good that rules those out. Let me look further. I assume you have checked all three fuses as well.
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Customer reply replied 10 days ago
sir I can get the fans to turn on manually they’re getting power if I use the check to and I go underneath the fence I can go in there and switch the fans on manually and they come on
Customer reply replied 10 days ago
Tech 2
GM Mechanic: Robert Blackwell,
 replied 9 days ago
Do they both come on low speed when commanded and high speed when commanded.
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Customer reply replied 9 days ago
They do
Customer reply replied 9 days ago
The right fan does not want to come on when the temperature starts getting hot to help the left fan cool And the right fan does not want to come on when the AC is turned on
GM Mechanic: Robert Blackwell,
 replied 9 days ago
I know it's simple but I have to follow all processes. The ac does come on when commanded inside the vehicle and high and low side pressure switches are not hotwired?
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Customer reply replied 9 days ago
no
GM Mechanic: Robert Blackwell,
 replied 9 days ago
This is leaning towards a PCM. Though you can command fans on through Tech 2 your using a different circuit inside pcm. Ac command runs through different drivers inside pcm. I would suspect AC circuit but fan relies on AC signal circuit only which is working because compressor is coming on. I have one last trouble shooting step to check wiring from pcm.At the pcm turn vehicle on amd turn ac on. Check for voltage at Connector 2 pin 33 dark blue. If no voltage is present check for continuity to body ground. If no voltage is present ecm is not grounding fan internally and will need to be replaced.
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GM Mechanic: Robert Blackwell,
 replied 9 days ago
I meant if voltage is present ECM is not grounding relay internally.
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Customer reply replied 9 days ago
What about the ambient temperature sensor angle is that have anything to do with it
GM Mechanic: Robert Blackwell,
 replied 9 days ago
No not as far as what the schematic says. I also just figured something out according to schematics. The right fan can come on buy itself but left fan grounds through right fan so anytime left fan is on so should right fan.
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GM Mechanic: Robert Blackwell,
 replied 9 days ago
One fan should have one wire coming from it. A yellow wire. Which fan is that?
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GM Mechanic: Robert Blackwell,
 replied 9 days ago
Well two wires. Gray going in and yellow coming out.
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Customer reply replied 9 days ago
That doesn’t sound right the left is supposed to be the primary fan on first and the right should be the aux and AC fan
GM Mechanic: Robert Blackwell,
 replied 9 days ago
That's why I need to know which fan has the yellow and gray wire. It doesnt seem right to me either. These are GM schematics though.
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Customer reply replied 9 days ago
Ok I will have to contact you back later when I get to the truck
GM Mechanic: Robert Blackwell,
 replied 9 days ago
Ok I'll be here. Let me know.
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Customer reply replied 9 days ago
Quick question if the ground was bad when the fan not come on at all
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