tahoe rear air has no heat- just blowing cold

[sandbanshee]

I have a 2004 Tahoe with rear air and no matter how I set the temp controls, it blows cold air. I found that the temp actuator in the back is not moving. Is there anyway to test if its bad? I put a voltmeter in the 5 different plug pins and it doesn't change whether i set it for cooling or heating. any help would be appreciated. thanks

[kcb37]

Sounds like you don't have any power then. Don't know if they have a fuse for the rear only, but wouldn't hurt to check.

[sandbanshee]

sorry, worded wrong. there is power on different pins (one has 3.6 V, one has 7.2 V, and one has 18V) but it doesn't change when i call for cooling or heating. I have no wiring diagram on this. don't know how the powers run???

[kcb37]

Don't know what to tell you.
The heating and cooling is a separate system in the rear isn't it?
I don't know how they work.

[wgr2112]

I didn't know Tahoes had reat heat, just A/C. That's the way my 98 is. Maybe that's changed. In the winter, mine blows cold, but it's good for circulating the air.

[KatDaddyJames]

do you have a temp selector for the rear or just a fan switch? if you are using the temp selector on the dash for up front, it will not control the rear, and if youdont have a temp selector for the rear it is a ac only system. i know obs tahoe/yukon didnt have rear heat, just rear air thus the front switch says rear ac.

james

[chrias]

I know the rear heater in my 2000 NBS Suburban takes forever to start blowing heat. Usually about 15 minutes. I know there is a replacement part the runs the coolant to the rear lines. It's actually bigger because the factory one is smaller and more restrictive. I remember seeing a TSB on it a while back.

One other thing you may want to check is the ground which is located behind the D pillar on the passenger side. The nut may have backed off a bit and it needs to be tightened down.

[MaineMudder]

I've replaced a few air temp actuators on the tahoes and yukons..your actuator has frozen itself and is no good..gonna break the bank for ya as if I can recall they are around $160.

[p.hinds]

this module has fixed this problem for me,,black box by the actuator...xTooltipElement Service Information 2004 Chevrolet Tahoe - 2WD | Avalanche, Escalade, Suburban, Tahoe, Yukon (VIN C/K) Service Manual | Document ID: 1887382
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#06-01-39-015A: Unable to Control Rear HVAC Temperature or Modes, Intermittent Ticking Noise from Rear HVAC Actuators or Rear HVAC DTCs B0434 or B3764 (Replace Auxiliary HVAC Control Module) - (Jan 12, 2007)


Subject: Unable To Control Rear HVAC Temperature Or Modes, Intermittent Ticking Noise From Rear HVAC Actuators Or Rear HVAC DTCs B0434 Or B3764 (Replace Auxiliary HVAC Control Module)


Models: 2003-2006 Cadillac Escalade Models

2003-2006 Chevrolet Suburban, Tahoe

2003-2006 GMC Yukon Models

with Automatic Control HVAC System and Rear A/C (RPOs CJ2 and C69)




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This bulletin is being revised to correct one of the blower motor control module part numbers. Please discard Corporate Bulletin Number 06-01-39-015 (Section 01 -- HVAC).


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Condition
Some customers may comment on one or more of the following conditions:

• An intermittent ticking/clicking noise from the rear Heating, Ventilation and Air Conditioning (HVAC) system.

• Unable to control rear HVAC system temperature.

• Unable to change rear HVAC system modes.

Technicians may find that Diagnostic Trouble Codes (DTCs) B0434 and/or B3764 have been set.

Cause
These conditions may be caused by HVAC actuators that hunt for the correct position. This cycling may cause a clicking or ticking noise.

An overtravel of the HVAC system control doors may cause one or more of the above system conditions. If an overtravel occurs, a DTC will be set, and the door will go to a preset default position.

When a system door defaults, that door will stay at the default position until the DTC is cleared. Clearing the DTC will allow the door to operate properly until the overtravel condition reoccurs. The following table lists the DTCs that may have been set and the door that is associated with that code.

Overtravel DTC
System Door Affected

B0434
Auxiliary (rear) Air Temperature Actuator

B3764
Auxiliary (rear) Mode Actuator


Correction
Technicians are to replace the auxiliary (rear) HVAC control module with the part number listed in the table below. Refer to the Auxiliary Heater and Air Conditioning Control Module Replacement procedure in SI for more information. This module contains a new calibration to compensate for the actuator overtravel condition and the hunting/clicking noises. The new calibration effectively eliminates DTCs B0434 and B3764. The new control module also eliminates the default position of the doors associated with the DTC. The new control module will allow door travel from counts 0 to 255 without setting a DTC or defaulting the door.

The new auxiliary HVAC control module is compatible with either the first or second design blower motor control module. When using the new auxiliary HVAC control module, the customer may notice a slight increase in the rear blower motor speed (approximately 50 rpm) at a given setting, as compared to the blower motor speed at the same setting with the original HVAC control module. If the customer comments that the increase in blower speed at a given setting is objectionable, the blower motor control module may be replaced with the second design part listed below to correct the slight increase in speed.

The revised auxiliary HVAC control module should not be used unless one or both of the DTCs are set or one or more of the conditions listed above are present. The revised auxiliary HVAC control module will not correct any other DTC or Air Conditioning (A/C) performance concern.

Parts Information
Auxiliary HVAC Control Module Part Number
Description
Qty

15832319
Module Assembly-Auxiliary Heater & A/C Control
1


The blower motor control modules listed below should not be used unless the customer finds the change in blower speeds between the original and the new auxiliary HVAC control modules objectionable.

Blower Motor Control Modules Part Number
Part Description
Vehicle Application
Quantity

89024926
Module Assembly, Auxiliary Heater & A/C Control (Auxiliary Blower Motor Control Module) (Second Design)
Escalade, Tahoe, Yukon (vehicles with a short wheelbase)
1

89018849
Module Assembly, Auxiliary Heater & A/C Control (Auxiliary Blower Motor Control Module) (Second Design)
Escalade ESV, Suburban, Yukon XL (vehicles with a long wheelbase)
1


Warranty Information
For vehicles repaired under warranty, use:

Labor Operation
Description
Labor Time

D0901
Module, HVAC Control-Auxiliary - Replace
Use Published Labor Operation Time

Add
With Third Row Seat

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.

WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION


© 2008 General Motors Corporation. All rights reserved.

[ksukats57]

Probably a bad actuator.

[east302]

Hey,

Ok, I've got a 2003 Tahoe LT with the auto a/c and the same problem.

The damper actuator in the rear was hunting back and forth and usually putting out hot air. I could see the indicator moving back and forth. The actuator controlling floor-ceiling air flow worked fine.

So I replaced it with a new module (Part #15832319) per that TSB mentioned above. That's the control module that tells the two damper actuators what to do. Well, now the hot/cold actuator is stuck on cold. The floor-ceiling damper actuator still works just fine.

I disconnected the battery for 30-minutes thinking maybe it was a trouble code causing it to stick. But no change.

Does anyone have any ideas? Right now, it's ok for it to be stuck on cold, but I'd really like to fix this if it's something I can do myself.

I'd appreciate any suggestions,
Scott

[p.hinds]

the actuator may have been over traveled.try centering the actuator.with the key on and the connector connected,jump the yellow and white/black wires.if it doesnt move jump the white/black to gray wire.

[east302]

Thanks, Hinds. Those are the wires on the harness to the actuator, right?

[p.hinds]

yes

[p.hinds]

forgot to mention when the actuator centers have someone ready to turn the key off.

[east302]

SOLUTION: To update in case anyone runs across this, replacing the hot/cold damper actuator fixed my problem.

[Godti]

Where abouts is the actuator located??

[east302]

The actuators are on the passenger side of the rear cargo area.

Here's a picture showing the parts from my 2003 Tahoe with auto a/c...



1- Hot/Cold actuator
2- Floor/Ceiling actuator
3- Control module #15832319 with the two blue clips

[Maxbaby]

Just to clarify what the "solution" was, you did first replace the controller module and THEN replaced the actuator, right? And did you have to reset the trouble codes to make it work or did it just start working properly without clearing codes?

[east302]

It started with no cold air in the back. Looking at the hot-cold actuator, it was hunting and staying mostly on hot.

Someone posted a TSB which sort of fit my problem and recommended replacing the control module. It's my understanding that the control module sends signals to the actuators to adjust the dampers. So I did this and the hot-cold actuator stopped hunting...but rotated to "cold" and stayed there.

On the advice of others, and hoping to reset the computer, I left the battery disconnected for a while with no change. I put the old module back in and the hot-cold actuator still stayed on cold--no hunting.

So I replaced the hot-cold actuator and it worked from then on. I suspect that the control module was fine all along.