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GMC Forum: 2001 GMC Sierra heater blowing cold air?
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Old 02-04-2010, 02:44 PM
cramsnomme cramsnomme is offline
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Default 2001 GMC Sierra heater blowing cold air?

my 2001 gmc sierra is blowing cold air, checked heater coil and its warmed up tried rocking it and nogo either. AC blows fine. No leaks at all. Is it the thermostat or water pump. plenty of coolant too.
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Old 02-04-2010, 02:44 PM
Matt M Matt M is offline
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If it was the water pump the vehicle would over heat or leak fluid I'm sure its the thermostat.. Can't fix it right away get a small piece of cardboard to cover up some of the radiator (( SOME of the radiator)) to get the heat working
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Old 02-04-2010, 10:43 PM
Molson02536 Molson02536 is offline
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Quote:
Originally Posted by cramsnomme View Post
my 2001 gmc sierra is blowing cold air, checked heater coil and its warmed up tried rocking it and nogo either. AC blows fine. No leaks at all. Is it the thermostat or water pump. plenty of coolant too.
Two common items I have run into that COULD be your problem
First would be the mode door actuator and cam assembly.
It is located on the drivers side of the HVAC above the gas pedal.
It is fairly diffucult to replace.
The other common problem I have run into is on the passenger side. If you remove the dash end close out panel
(the panel up against the passenger side door). Inside there there is about 6 electrical connectors.
You need to find the (12) wire brown colored one (C4), the 6 wire brown (C5) and the 6 wire gray (C8). All the terminals need to be checked for backed out terminals, bent pins, loose or poor terminal tension.
Also if you open the glove box, to the left you'll see a small wire harness taped, going down.
That wire MAY rub against the metal dash frame and be shorting out. It too can cause your problem.
IF POSSIBLE, I would take it to a good shop your familiar with and have them scan the HVAC system for Trouble codes. If any of these codes are stored (B0229 B0263 B0268 B0408 B0414 B3770) You may have either of the 2 wiring issues.

If your wire harness is good then your temperature control actuator is bad. It's a little motor that moves the temp door. They are about $70 at the dealer. To change it you need to remove the knee trim panel on the passenger side (3 screws, 7mm socket). The actuator is in the center above the transmission hump. It has one harness plugged into it and 2 screws (5.5 mm). Take the screws out and it should drop straight down. Align the actuator with the lever on the door and put the screws in. Plug the harness back in. Turn your temp control to cold and remove the HVAC 1 fuse. Should be in the fuse panel on the drivers side of the dash. Turn your key to run and leave it on for at least 1 minute. Turn your key back off and put the fuse back in.
P.S. The trim panel is a PITA to get off, so while you have it off check to see if you have the cabin air filters and change them while you are under there.
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Old 09-10-2011, 06:52 PM
steak2k1 steak2k1 is offline
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Default HVAC Actuators and issues..?

Molson...wish I had read your post a few days ago. I have been searching for an answer to my issue...similar to the one above..or it may well be the same issue or even a series of problems:

2006 D'max/Ally CCSB dual zone HVAC..

In winter time, I live in Calgary, the drivers side vents will only blow cold air with the pass side acting normal providing (warm/hot), air at the temp that I set it. My temporary fix was to remove the battery cables - let sit for 5 min and reconnect - system recalibrates. Now with winter fast approaching, my research on this issue led me to believe it was in fact a blend door actuator that was faulty. I replaced the unit that is above and behind the fuel pedal..not easy but got it done. My first time out, It would provide hot air. turn truck off for the night and I come out this morning - no joy..same issue.

Interestingly enough the new Actuator is GM PN: 8901-8365 (old # 5402-2588). When I look at the old actuator it has a PN on it: 5402-2598. Yet I do believe that these are one and the same part.

Also..take a look a the position of the indicator on the old actuator..It seems it is gone beyond its normal travel.?

[IMG][/IMG]

here's the new one that I installed:

[IMG][/IMG]


I will look at the harnesses that you mention...but suspect it is the temp mode actuator that is the culprit..??

There are also some posts here and there (am long time member of dieselplace.com), that suggest there is a reflash of the HVAC control module..to rectify "clicking"..I dont have that issue but wonder if a truck with a build date of Oct 05 would not have had this flash software installed during the build.

Any comments or advice is greatly appreciated.

Thank you,

Theo
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Old 09-10-2011, 07:06 PM
steak2k1 steak2k1 is offline
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Default Additonal info on hot/cold air blowing

Molson...I neglected to inform you the truck has 337,950km's. No other major issues except the chronic ones:

ISS - fixed with new teflon ISS - my cost $250.00

Leaking Trans lines - fixed for third time at my cost ($650.00) SSteel braided lines-teflon coated - 2 part threaded for easy removal.
Pump rub on Trans Case - fixed at my cost..glad I caught that in time. ($350).

There's a couple of issues GM needs to correct...but are they listening.??

Other than a few bearing assys, 2 CV shafts...no motor or Allison issues or anything else....until this HVAC actuator thing.
thanx,

Theo
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Old 09-10-2011, 07:08 PM
steak2k1 steak2k1 is offline
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ok...what the heck happened to my original post..?? wierd. Guess I'll wait and see if it re-appears from cyberspace.! \so I try to repost and it too dissappears...whats up with that folks.?? Im trying to get some answers here and for some reason every time i add a cpl of pics, my post disappears not to be seen until when..a mod checks it out.?? Well...i look for mods and there aint none on. sheesh.!

stk

Last edited by steak2k1; 09-10-2011 at 08:13 PM.
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