In this video I have a look at an older GMC Sierra that had a customer complaint of the HVAC being stuck on defrost. My gut told me "prolly just a bad actuator." However, the data showed us something different.
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Due to factors beyond the control of South Main Auto Repair, it cannot guarantee against unauthorized modifications of this information, or improper use of this information. South Main Auto Repair assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. South Main Auto Repair recommends safe practices when working with power tools, automotive lifts, lifting tools, jack stands, electrical equipment, blunt instruments, chemicals, lubricants, or any other tools or equipment seen or implied in this video. Due to factors beyond the control of South Main Auto Repair, no information contained in this video shall create any express or implied warranty or guarantee of any particular result. Any injury, damage or loss that may result from improper use of these tools, equipment, or the information contained.
If an SMA Video has helped you out please consider giving using "Patreon" to help support us. The videos take real time to create and pull us away from real work that pays our bills. CLICK HERE: https://www.patreon.com/southmainauto
CHECK OUT OUR "SMA SWAG" STORE! Go on Teespring and get your very own SMA merch!
https://teespring.com/stores/the-sma-store
If you don't like Patreon feel free to use the "PayPal Me" link: https://www.paypal.me/SouthMainAuto
The South Main Auto Amazon Store:
https://www.amazon.com/shop/southmainautorepairavoca
AES Wave Automotive Diagnostic Tools: https://www.aeswave.com/cart.php?m=affiliate_go&affiliateID=2525b91fc8e906e8215984074c9d9e8f&go=https://www.aeswave.com/Miscellaneous-p9347.html
Thank you for all the continuing support!
--Eric & Vanessa O.
Feel like sending some swag to SMA because you love the videos but don't know where to send it?
Just ship it here:
South Main Auto Repair
47 S. Main St
PO Box 471
Avoca, NY 14809
Disclaimer:
Due to factors beyond the control of South Main Auto Repair, it cannot guarantee against unauthorized modifications of this information, or improper use of this information. South Main Auto Repair assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. South Main Auto Repair recommends safe practices when working with power tools, automotive lifts, lifting tools, jack stands, electrical equipment, blunt instruments, chemicals, lubricants, or any other tools or equipment seen or implied in this video. Due to factors beyond the control of South Main Auto Repair, no information contained in this video shall create any express or implied warranty or guarantee of any particular result. Any injury, damage or loss that may result from improper use of these tools, equipment, or the information contained.
I love you now
Could you recalibrate?
Eric, you are the man brother 🙌
Thanks!
I want to thank you for such a great review of this issue. I have been trouble shooting this same issue on a 2002 2500HD for a month. I replaced the actuator for the same failure and had no change. Still stuck when switched to defrost.
After watching your video, I went back and checked signal voltage again with the same 5v shut off at defrost. Added the screw to motor housing and it works perfect.
Who would have thought that foam seal could cause this much of a problem. Thanks again.
Thanks. Helped out a lot. Have the same problem on an 02 silverado
Genius fix! Thanks
Nice job…I feel much more informed now..good Ole technical know how
Great video brother going through the same deal was suspected it bit you verified thanks a bunch
Thank you, This problem just started on my 2001 Chevy Silverado. granted I don't have any foam dust but at least you gave me some ideas where to look.
I'm hoping that customer decides to continue fixing the HVAC on his 2001 GM 1500, I have the same model year and have yet another non-straightforward repair needs with mine. Mine is actually in the recirq actuator, which you touched upon it wasn't showing the proper functionality, but never went any further into it. Mine, I have gone all the way up in there, changed out that actuator, only to have it exhibit WORSE functionality… it opens the door when commanded to close it, and vice versa… it also commands the compressor to run when recirq is commanded, but the door is closed. I opened up the old actuator and found a split nylon drive gear, which I was able to rotate 180 degrees so the damaged teeth won't be in contact with the other gears. Now I've just gotta totally tear apart the dash again (including cutting through the far right side panel duct, which it only taped back together now with foil backed duct tape) and swap this repaired OEM actuator back up in there.
I find myself watching at least one if ur videos most every day! I've been subscribed for over 6 months now and still I find you keep it interesting, at least enough to keep my interest. If I wasn't all the way out here in SF I'd for sure pop in ur shop fora chat… Who knows when I might be back there upstate way! BTW… my daughter spent 4 years at Marist in Poughkeepsie back in the 2012-2016 timeframe… If I knew about y'all back then that would've been the chance to visit, huh?
I came back to comment, that now, on my 2006 GMC yukon the recirculation door was stuck on fresh air only. I was able to pull the digitial climate control brain out and ground the low reference yellow wire and with the ignition in the "run" position I gott the door to move to recirculation. Then through the blower motor access hole I was able to glue new weather stripping to the door so it no longer overtraveled and now it works like it should. Even if the foam does not deteriorate what ends up happening is that it looses it's memory and stays compressed thus allowing the door to move too far – stupid design!
EXCELLENT VIDEO, EXPLANATION, CLARITY. you are awesome buddy
thanks for sharing
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My son has a diesel truck with small electric vacuum pump for heater control and at runs constant. He has replaced 3 times because it burns up.
Great job , mines keep going out in defrost mode 40 year diesel technician, replaced twice but in the morning going to jump reverse wire remove in install 3/32 dowel pin thanks
Love the video. Simple, honest and, funny.
Thanks to this video I got my truck fixed because it was doing literally the same exact thing as this truck I tried everything but once I watched this video I knew exactly what was wrong and how to fix it I had the same intentions to what you had when you were diagnosing this truck I’m glad you made a video about this because no one else did
Blend doors suck, especially since they make them virtually untouchable in most vehicles without tearing the whole dash apart.
Excellent video!
I applaud your skills!
Unbelievable detective work!
You should change the name of your channel to “The Educated Mechanic”.
Plus, plus, you even speak your native tongue correctly – see, saw, seen, does, don’t, doesn’t, very unusual in todays sloppy world.
Thank you for your efforts and your ability to show how you research different problems.
🙏🏻🙏🏻🙏🏻🙏🏻🙏🏻🙏🏻
Great detective work Eric. Outstanding. Keep those videos rolling.
As usual Eric you are a source of Education on these blend door's for the AC and heater systems unlike the old cables .
I will be watching for foam up on the dash of my Tahoe, thanks.
there is a RESET process for GM trucks to learn the blend door open and closed limits.
Hemc Eric
New York miles and Arizona miles are two different things. The foam fell apart not the frame and body
Great video
Very interesting approach to solving the riddle! I have a 2004 Silverado that had the same issue – defrost only. Bought it used, did not know the history of the vehicle. Paid the diagnostics fee at the dealership, yup, that's right paid the diagnostic fee at the dealership to verify it was the mode door actuator. The tech was very knowledgeable and helpful. As you said re the mode door there is no wire to be able to monitor it without probing it as you did. He told me the mode door actuator failed, provided me with the schematic printouts for the system same as you showed following the colored wires. I bought a mode door from the dealer and left lighter in the wallet. I installed the actuator myself, bugger to get to and install getting the gear and dowel slot lined up. I tested the old actuator with an old 9V battery, it would rotate both ways, as the tech had said it was the feedback that was likely the issue. Fast forward about 3 months and the actuator failed again! Back to the dealership and spoke with the service department about the issue. They advised that as they diagnosed the issue, even though I installed it, it would be covered under the parts warranty. Fast forward since March 2020 ( yup, March 2020 ) and the actuator has not acted up since. My truck just turned 280,000 kms, so like 175,000 miles. Since march 2020 I have been working from home so the truck doesn't get used like it used to driving to work every day.
I admire your approach to verify before throwing parts at it, my hats of to you. Should the actuator act up again I have more insight into how to prevent replacement, thank you. Mine hasn't blown out the door sealer foam dust, it doesn't get that hot up here in Kanuck-ville, and the winters begin in Oct and leave in April. Thank you for an informative video, I've watched many on the "GM Mode Door" issue. None of them were much help, that changed today. Cheers Mate!
My 98 Silverado is doing pretty much the same thing except the little levers that slide in the guide groves broke. And my AC just stopped working all together so now the heater works on high only all other functions have stop completely. I generally don't mind working on my truck… But I'm not about to take that whole dash out…. Any thoughts on a quick fix?
Mine just started not working and this was the perfect vid. Now I know what I need to do to start the repair.. appreciate your time and effort makin the vid…😉
I just love these puzzling ones and how you figure it out. Great video.
Had the same problem on a 2000 silverado GA truck 360k miles, I was just gonna live with it. Thank you so much
what happen to cables
Wow! You’re Einsteins lost brother😆
Excellent troubleshooting, did you get approval from the shop owner to add the screw to the door motor. lol.
THANK YOU!!!
Been messing with this for a while, this makes sense
Odds are slim I would have ever thought about the insulation on the blend door causing overshoot and loss of control. Great attention to detail. Wish I knew where you get your wing diagrams and tech data. Thanks.
Have you don’t a video on the hot and cold blend door? I think that’s the hard one in the middle of the dash on passenger side.
I’m having a similar issue but I’m not getting anything out of the mode door or the temp door. I see in the diagram that the grey wire goes to both, I have replaced both actuators but no good. Do you have any suggestions?
Simple , only takes a genius , to do it !!
Watched video a second time and got one question answered – I think. The red box is a U-Scope? However, a bunch more questions arose.
1) Where did you get the theory of operation and wiring schematic from? (I'm a computer nerd so don't know how to ask questions properly on Google)
2) Where did that 4amp bulb come from? Where was it plugged into and with what did you plug it in?
3) You mentioned that you popped that black actuator assembly off – how did you do that?
4) You also mentioned that you stuck your thumb up 'there' to prevent the mode door from going past its intended stopping point. Where is 'there'?
5) Would the mode doors stuck on defrost affect the cooling ability of the A/C? (I don't think it should)
6) Question review: How was U-Scope hooked up? Where to get it and how much?
1) didn't catch what that red box was called
2) never saw how it was hooked up
3) where does one get it and how much?
GM HVAC systems are always having issues. My silverado doesn't like to switch modes when it is extremely cold out, otherwise it functions perfectly fine. When it completely warms up (about 45 min) it will start working again if i cycle the key. I literally just changed the mode actuator, lets hope it works.
Eric, I do not know how your head hasn't exploded with all the knowledge you have stuffed in it .lol.
Joking but you are my go to guy on you tube . I share your site with all my friends that can benefit. A few are mechanics ( not at your level…my opinion ).
You rock !
These trucks are lemons..my 2002 is a youtube truck..I have to watch so much youtube to fix the endless electronics…seats,dash, lights, now heat..my dash is working now but still no dash lights..and I just jammed the heater door so I get defrost and heat everywhere.
Wear, deterioration and Meeces! Ask me how I know. Love to live in those boxes!
I am shocked this channel is not over 1 million subscribers. Great job!
Gm controls are IMHO pretty iffy. On my mom's 2001 Malibu the AC switch quickly wears out. One repair is to rub a graphite pencil over the AC button contacts. Sure beats paying high double digits for another iffy control.
Guess I failed to mention in the video that customer had all ready purchased a new OEM actuator. Just to be sure I wasn't crazy I tried it but knew it wasn't gonna work from our test results. He told me to just leave it in because he already bought it. 🤷♂️