What controls what?! - Chevy and GMC Duramax Diesel Forum
2001 - 2007 (GMT800) Non Powertrain Discussion of 01 to 07.5 Topics Not related to the Powertrain, interior, suspensions, body,wheels, tires, ect.

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post #1 of 20 (permalink) Old 01-13-2020, 01:01 PM Thread Starter
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What controls what?!

Hey everybody, I have a 2005 LLY with digital dual climate control. I’ve spent a lot of time trying to figure out this fix but need a little help. I have the very common “hit a bump and climate control goes haywire”. My question is can anybody tell me what actuator controls what function? I fixed where the air is directed by replacing the actuator above the gas pedal. I swapped the actuator behind and to the right of my console and that seemed to fix the passenger side heat/cool issue but I’m still having a problem with the drivers side blowing heat then blowing cold when I hit a bump. Where is this actuator that controls drivers side heat/cold? Thanks in advance!

2004 Chevy Silverado 2500HD CCSB 4x4
LB7 w/ about 213k mi
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post #2 of 20 (permalink) Old 01-13-2020, 04:31 PM
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Here's a pic....there are 4 actuators...and I think they're all the same part number, but in the pic below, they have different number I.D.s

26 handles the intake air/recir
10 is probably the one you got to on the drivers side for directional.

Two #4s, one below working #15 paddle and another above working #13 paddle...you got the low one on the hump....don't remember if you have to pull the whole dash, but pulling the radio / hvac control module might gain access to it.
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post #3 of 20 (permalink) Old 01-13-2020, 05:08 PM
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#4, bottom of diagram, over the hump is the drivers side - and the easiest one to get to. A little 1/4" drive thumb wheel is what I used to get the bolts out (7/32" IIRC). #4 on top of diagram is the passenger side - I had to get to that one too. All day project. There is a you boob video of a guy showing how to open up and clean contacts in actuator. I followed it for my driver side - glitch free for 4 years now, but bought a new one for passenger side as I was in no way opening up the the whole dash cover again.

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2005 CC Sierra - 366k and strong, Son's ride now (but I'm not signing over title just yet)
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post #4 of 20 (permalink) Old 01-13-2020, 08:11 PM Thread Starter
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Ok so yes thanks for that diagram! I did the #26 and the #4 on the bottom already. The passenger side now works as it should but it’s the drivers side air that starts off where I want it but when I hit a bump in the road it flips from hot to cold and won’t come back to hot again. So seems to me the top #4 (the one I haven’t touched) is the bad one controlling the drivers side rather than the bottom maybe?

2004 Chevy Silverado 2500HD CCSB 4x4
LB7 w/ about 213k mi
Edge Juice w/attitude
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post #5 of 20 (permalink) Old 01-14-2020, 03:00 PM Thread Starter
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Ok well of course you were correct. Bottom over the trans hump controls temp on drivers side. I took it out and noticed my brand new actuator somehow got screwed up and the gears had slipped out of whack allowing the main drive gear to move whenever it wanted. Cheap parts. I swapped it with a different one. It moves like it should but even recalibrating the system it appears as though my climate control just does whatever it wants to. Doesn’t matter what I select, sometimes the actuators move sometimes they don’t. So with that could my climate control main unit just be bad?

2004 Chevy Silverado 2500HD CCSB 4x4
LB7 w/ about 213k mi
Edge Juice w/attitude
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post #6 of 20 (permalink) Old 01-14-2020, 04:18 PM
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Yes its possible. Anything else acting wacky interior wise? A questionable or intermittent ground will make all sorts of strange symptoms. GM Upfitters website has pretty good wiring diagrams - specifically one page showing ground locations. Worth checking - costs nothing. You said bumps would change things - I would check out all the connectors for loose or bent pins.

2016 Denali

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post #7 of 20 (permalink) Old 01-14-2020, 07:21 PM Thread Starter
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Yeah good point, the only other strange thing that goes on is sometimes (not often) if I turn the ignition key to the “run” position but don’t crank the engine, it automatically starts the truck. Maybe I do need to chase down some wires.

2004 Chevy Silverado 2500HD CCSB 4x4
LB7 w/ about 213k mi
Edge Juice w/attitude
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post #8 of 20 (permalink) Old 01-15-2020, 12:23 PM
 
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If the temp is changing when you use the controls and the actuators are moving correctly, but changes when you hit a bump it isn't necessarily an actuator issue or wiring issue. It very well could be a broken blend door in the heater box.
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post #9 of 20 (permalink) Old 01-15-2020, 01:15 PM
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Originally Posted by ThreeMs View Post
Ok well of course you were correct. Bottom over the trans hump controls temp on drivers side. I took it out and noticed my brand new actuator somehow got screwed up and the gears had slipped out of whack allowing the main drive gear to move whenever it wanted. Cheap parts. I swapped it with a different one. It moves like it should but even recalibrating the system it appears as though my climate control just does whatever it wants to. Doesn’t matter what I select, sometimes the actuators move sometimes they don’t. So with that could my climate control main unit just be bad?
It is common to see trucks with clusters that need to be resoldered but this can happen on any components including the HVAC circuit board. The unit may be working fine, but it may have some bad solder points that have broken off from a decade and change of heat cycles. Like with the cluster, often all they need is to have the solder pads reflowed with a soldering iron and some new solder (i would use lead) and they may work normally again. Worse case, assuming you dont physically break something, your out an hour of so of time and a few inches of solder.


In the event that you were to find something like this, which is possible, you would need to scrape the green solder mask off the trace leading to the solder pad, and then solder that connection to the trace and bypass the lifted solder pad.



Edit: looks like that picture is from a site with step by step instructions to repairing PCB delams so ill just post the link to that as well just in case its helpful. I feel like the fix shown on that site is very good, but also overkill for our application. simply soldering to the trace would be fine if thats what it ended up being.

https://www.kitronik.co.uk/blog/simp...-board-repair/



Lastly, it may just be time for a new HVAC control. If you have a friend or know someone with the same trim truck (diesel or not) you should be able to swap heater controls to test if there known working one has the same issue in your truck. If the issue persists post swap, its not the HVAC controls.
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2015 Chevy Silverado 2500 HD 6.6L LML

Last edited by J83; 01-15-2020 at 01:19 PM.
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post #10 of 20 (permalink) Old 01-15-2020, 01:21 PM
J83
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Yeah good point, the only other strange thing that goes on is sometimes (not often) if I turn the ignition key to the “run” position but don’t crank the engine, it automatically starts the truck. Maybe I do need to chase down some wires.
Electrically, this should not be possible on your year of truck without some electrical failure. You would have to have the white, pink, brown or orange ignition wires shorted to the yellow ignition wire, or have a short in the fuse box that jumps the starter relay off ignition or something. On the pre 2007.5 trucks the starter circuit is high current from the key, to relay, to solenoid to starter. Ignition and accessory are not a part of the starter circuit until the new trucks started after 07.5.

Based on this information i would take a look at your fuse box (under side of under hood, and back side of in cab) for any damage from mice / moisture ect. and id look under the driver dash for any signs of similar damage to the ignition wires. They should be 14-12 gauge wires running to the key switch and then to a bolted in connector near the BCM.

your ignition wires should function like this.

Red - Hot always
Red 2 (may have white or black stripe) - hot always

Pink - Ignition 1 - Hot in run and start
powers main engine ignition circuit
White - Ignition 2 - Hot in run and start
required, but truck will start without it, will damage transmission if not powered.

Orange - Accessory 1 - Hot in Run and accessory, drops out in start
NOTE: this is power to the HVAC system
Brown accessory 2 - Hot in Run and accessory, drops out in start
Powers wipers, radio, non critical systems.

Yellow - Starter - Hot in start position ONLY.
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Last edited by J83; 01-15-2020 at 01:28 PM.
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