2016 Yukon Denali A/C Heater Blower

[arkie]

Blower will give short burst of air when turned on from off position, then fades quickly at all speed settings.
Evidently all fuses are good.

Rear blower works normally.

Any suggestions?

 

[arkie]

Searching now for a good wiring diagram, appears that there is no resister/control module for the front blower and may have that functionality incorporated into the blower itself. Can anyone tell me what the upstream component is that supplies the PCM signal for the blower?

 

[Fless]

Not likely controlled by the PCM. Maybe the BCM through the HVAC head. But you should have a blower motor resistor near the fan motor. Disconnect the blower motor and apply 12v from a car battery or a 12v tool battery and test it that way. If it runs full blast and doesn't fade, then the resistor probably needs to be replaced.

Probably one of these, but my money is on the blower motor:

 

[arkie]

The parts diagram does not show a resistor / control module for the front blower. It does for the rear/auxillary blower.
The blower actually has 3 wires on the connector, Black, Red, and a light blue (i think) -- dark and hard to see.
I believe the resistor functionality has been replaced with a Pulse Code Modulation (PCM) signal to control the ground side of the circuit.

On the rear unit, there is a separate, resistor/module that recieves the PCM signal and switches the ground on and off to create the variable speed of the blower.
Since the front blower has the third wire at the connector, I am assuming it incorporates the resistor function into the blower.

If it is, as I believe, a PCM signal, i probably cannot get a good reading with a probe or multimeter. But will be trying both tomorrow. Will also be checking the 12v and ground wires for continuity.

I have also eyed those parts you listed, and compared with the GMpartsonline diagrams. Looks like the Denali is a little different.

I'll update on the voltage checks tomorrow.

Thanks for the post.

 

[arkie]

My problem is solved I think. A new blower (GM 84418890) will solve my problem I hope.

Checking at the connector to the blower shows good B+ and gnd. I cannot check the speed signal from the HVAC control module with my tools, but the signal going to the rear blower works fine. A gamble that the HVAC module is good on both signals I guess.

When I removed my blower I did find that it was wet from a leak some where in the cowl area, guessing that this shorted out something on the circuit board on the blower.

In case someone else runs into a similar problem, the attached pictures will show what this blower and circuit board looks like
BTW the tag on this OEM blower says made in China.

 

[Prospect62]

Arkie did the blower solve your issue? I am dealing with the exact same thing in my 2016 Suburban.

 

[Prospect62]

Well, if anyone else finds this who is experiencing a similar issue, a new blower motor also solved my problem. I was having the same exact symptoms as the OP. Blower would come on for a second or two then shut off, regardless of fan speed or defrost/vent/floor settings.

Don't go crazy looking for a "blower motor resistor" either, because there isn't one on these 15-20 trucks, despite some people here claiming otherwise. The rear blower has a resistor but NOT the front.

Like the OP, my truck also shows signs of a leak getting into the blower motor from God knows where and corroding the circuit board.