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Gary
Gary, ASE Certified Technician
Category: GMC
Satisfied Customers: 15707
Experience:  GCM master tech over 25 years
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2004 GMC Yukon XL Denali - no power to rear blower or blower

Customer Question

2004 GMC Yukon XL Denali - no power to rear blower or blower control. automatic blower speed. Fuses check good. I do not find any relays for blower systems. Front blower works as it should. No power going to the rear connecter. Wires come down from ceiling.
Submitted: 1 year ago.
Category: GMC
Customer: replied 1 year ago.
Can anyone help with were to look? Where to purchase a layout of the relays, wiring routing and connector locations. would be?
Expert:  Chris (aka-Moose) replied 1 year ago.
I am sorry for the delay in getting a response to you. Sometimes we get alot of customers and just can not keep up. Sometimes you just have to wait for the correct tech to login.
Do you even still need help. Sometimes customers seek help elsewhere or figure it out on their own before we get to each and everyone.
I am sure I can help a lot or a little at least something if you give me a chance and work with me. I am going to get an answer to you regardless if you reply or not sooner or later.
If your concern is urgent reply and let me know and if you have anything more you think will help me, to help you, let me know. I work on here normally 3pm-3am central.
Thanks Chris
Customer: replied 1 year ago.
I am still looking for help. I find the local shops expensive and useless. I need to know where to look for the problem with the wiring issue. Cold be under dash or some hidden connecter. The system worked two weeks ago then stopped working on a trip. Fuses were checked. Fan motor checked. No power going to the speed controller next to the motor. Following wires back no power at the connector going into the ceiling of the vehicle. Need someone who knows where I need to look on this vehicle.
Expert:  Chris (aka-Moose) replied 1 year ago.
Hi
Below is the wire diagram file.
https://dl.dropboxusercontent.com/u/90220402/04yukonAC.pdf
Can you remove the rear blower control and verify the orange wire has no power and the black/white is a good ground?
You want a excellent 5 star answer & I would like to be rated the same for providing it. Consider I don't know your skill level & I can't see, smell, hear, or touch the vehicle. It may take a few back and forth replies. Try your best to respond with good detail so I can do the same. I normally log in at 3pm and work late. A rating is required. Your rating me, what I type. I am not an employee of this website, nor have control over the fees or the time it took to get a response. If you rate negative or not at all you still paid, but I get nothing. I want you pleased with me and my efforts, so let me know if your experience here has come up short.
Thanks Chris
Customer: replied 1 year ago.
Thank you for the schematics, this is of help. The schematic is missing connectors that are between the fuse and the speed controller - connector locations would save me from pulling down the ceiling to follow where the wires and connectors. There is no power to blower speed controller however the fuse has been proven good - both sides of fuse has battery voltage so the issue is in between fuse and speed controller. All Connectors visible within qt. panel check good. There is no black and whit wire only orange, purple and black. Here is my current status: Ran external 12 volts ( plus and minus ) from battery to rear blower. Fan runs fine - fan ok. Ground verified between speed controller and chassis bolt. There is no corrosion anywhere around rear blower area. I now suspect another connector in ceiling near third seat overhead light as both the orange power and purple signal wires appear open. I am currently stumped and looks like I will need to remove all internal trim. Do you have any suggenstions or some kind or wiring diagram showing connector locations?
Customer: replied 1 year ago.
Side note. After this work the vehicle is dead. Second time in less than a year, last time was with a defective fuel pump and had car towed to shop. After recharging battery no issues other than defective fuel pump was found. Current heavy thunderstorms stopped me from checking this issue out and I have no idea why no dash, body lights or starter function 20 minutes earlier head lamps came on fine. maybe defective battery - will know more about this tomorrow. I will disconnect battery for a full system reset.
Expert:  Chris (aka-Moose) replied 1 year ago.
If you power the controller, does the blower now work correct?
Connector 397 is the only inline connector on the orange wire and it is behind the RR quarter trim panel above the auxiliary blower motor.
https://dl.dropboxusercontent.com/u/90220402/conn397.pdf
https://dl.dropboxusercontent.com/u/90220402/con397.pdf
Customer: replied 1 year ago.
No and as stated no power anywhere in rear blower - I can only assume connector 397 is the connector between the wires from the ceiling go through to get to the speed controller. As stated no power there.
Customer: replied 1 year ago.
Do you have anything showing how many and locations of all connectors involved to get power and signal to the rear?
Expert:  Chris (aka-Moose) replied 1 year ago.
Below you can see the connector 397 between the fuse and rear control.
https://dl.dropboxusercontent.com/u/90220402/c397view.png
Customer: replied 1 year ago.
Thank you for this drawing however this shows the front controller with the orange coming off a 10 am fuse no the 30 am fuse the first schematic you sent shows for the rear shows - no correlation.
Expert:  Chris (aka-Moose) replied 1 year ago.
You mentioned there was no ground black/white wire, so I assumed that diagram was incorrect, so I swapped over the GM files. The orange wire in the prior image is for the auxiliary controller.
Customer: replied 1 year ago.
Only your schematics were correct for my vehicle none of the following drawings are applicable. It is late now so I will not answer until morning or after work depending on what you find. Keep in mind that only three wires come down from the ceiling right rear corner for the rear blower, orange power, purple signal and black ground. I am not sure if the ground connects to the stud or continues up to the ceiling.
Expert:  Chris (aka-Moose) replied 1 year ago.
Since my files are not accurate, I will opt out and let another try to help. I see we are making no progress.
Customer: replied 1 year ago.
Can anyone pickup on this. Chris provided the schematic however the drawings showing the connecter locations near the rear air handler were incorrect. The heavy orange wire from the blower speed controller goes through a connector in the right rear corner of the vehicle into a wire harness up the back corner of the left panel and disapears above the head liner in the apparent direction of the third seat overhead lamp,. The black wire from the speed module goes to a stud on the frame. The thin purple wire goes to the to a wire harness near the connector the orng wire goes through but doubles back into another wire harness towards the temperature controller motors.
Customer: replied 1 year ago.
Still need assistance. As a recap. I ran a fused test wires from the battery to the rear and connected to the fan. The fan blows strong. I then connected to the fan speed controller - no fan. While trouble shooting the fan controller the vehicle battery failed and had to be replaced. I repeated test to speed controller however still no blower. Continuity test through all connectors involved proved good connections. It may be that the connector Chris mentions is the connector in the right rear corner of the vehicle in which case the connector is good however no power at the connector.
Customer: replied 1 year ago.
No one can help with GM auto electric issues?
Customer: replied 1 year ago.
In 2010 someone else had same issue - I can not obtain the drawings - can some else post the drawings showing connectos such as C206 and other related connector locations?
Customer: replied 1 year ago.
(Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Expert:  Gary replied 1 year ago.
new expert here did you still need help ?just to recap the rear blower will not work at all and the orange wire at the rear blower resistor/processor shows NO volts ?
Customer: replied 1 year ago.
Hello, Thanks for picking this up. This has a motor speed controller - not a resistor divider and yes there is no voltage anywhere in the back for the blower. Orange and control are both zero volts, eternal 12 volts across blower and the blower runs. external 12 volts to blower speed controller and no power to blower - probably due to no signal on the purple wire. The drawing provided does not show wiring as in this vehicle however the schematic provided looks correct. Blower was running on high speed when it stopped working. Fuse is good, swapped out with known good fuse in fuse panel.
Expert:  Gary replied 1 year ago.
and i am assuming the fuse called RR HVAC a 30 amp fuse is good in the under hood fuse box and shows 12 volts on both sides of that fuse testing it in place ?if so did you find connectors C397 or C206 to test for 12 volts at the orange wire at either connector ?
Customer: replied 1 year ago.
As just stated the fuse verified good by swapping out with a working fuse and measuring both sides of fuse with a dmm. I have checked the connectors in the back that the power to the blower passes through but no idea of connector numbers. I have no idea where connectors C397 or C206 are located as the connectors do not have labels
Expert:  Gary replied 1 year ago.
ok lets check connector C397 first here is the location of C397 and it should be terminal # ***** in that connector see if the orange wire has 12 volts in and out of the connector
Customer: replied 1 year ago.
Ok Connector C397 is in the rear area and there is no power at C397 - no power on any orange wire in the back lower
Customer: replied 1 year ago.
Where is this connector called C206?
Expert:  Gary replied 1 year ago.
ok then you need to get to connector C206 and terminal A6 see if it has power in and out of the connector C206
Customer: replied 1 year ago.
How do I access C206. Is this a connector on the firewall?
Customer: replied 1 year ago.
Looks like Number 9 on the drawing
Expert:  Gary replied 1 year ago.
yes # ***** under the passenger side of the dash near the fire wallno its not on the fire wall its a stand alone connector there
Customer: replied 1 year ago.
Looks like I need to pull the dash apart to access - does this connector mate to another wire harness?
Expert:  Gary replied 1 year ago.
you should be able to get to under the passenger side of the dash
yes its just a harness plug into connector that plugs into another harness
Customer: replied 1 year ago.
Drawing shows harness above air bag which does not provide space for hand however there is a discrepancy with the drawing. The drawing shows a fuse block - number 13 - where this vehicle has a connector pack. Could this be where the connectors are located on my vehicle?
Expert:  Gary replied 1 year ago.
it is more so between the heater box and fire wall area up @ 10 inchesno its located where the picture shows the connector to be # *****
Customer: replied 1 year ago.
That location is not accessible without taking the dash apart. What little room I have to work with does not show a wire harness up there.
Customer: replied 1 year ago.
To take the dash apart will take a little time.
Expert:  Gary replied 1 year ago.
at this point we have to find that connector and test for 12 in and 12 out of that connectorif it has 12 in and 12 out then the orange wire between C206 and connector C397 is broken or badif at connector C206 it does NOT have 12 in and out then the orange wire between C206 and the under hood fuse box is bad usually under the fuse box under hood is where we sometimes see small animals chew through wiresif you have 12 in but NOT out of connector C206 then the terminals are bad in the connector C206
Customer: replied 1 year ago.
I understand about the connector troubleshooting - no damage is found under the fuse box in the engine compartment... I ran a fused wire from the battery to the back corner of the vehicle and verified the fan works, spliced the wire into the orange at connector C397 however there still no control voltage to the motor controller - no fan. This would indicate a common problem. C206 is a likely location however I have yet to find this connector. Based on the number of wires going through this connector it should be a fair size connector and wire harness. The main wire harness going through this area has a couple small harnesses going up to the top of the dash but nothing with enough wires for C206 - so far. The black box for the front dual air conditioner pretty much fills all space between the firewall and the trim I am having problems figuring out how to get the dash apart so I can see all that is up there. I may need to disassemble the console first. Do you have something showing how to disassemble the right side dash?
Customer: replied 1 year ago.
Do you have any drawings showing the route of the wire from C206 to the rear of the vehicle? Does the wires go through the floor channel rt front door then up to the ceiling between the right front door and the right rear door?

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