Temperature door

unlucky · August 25, 2004

Here's my problem in a nutshell. I have a 2000 Sierra

Sometimes, after running the heater for a long period of time, the temperature control no longer works . . . even though you may select the coldest temp, the air still blows hot.

I can turn off the ignition for a while and let the engine cool and the tempurature control will start to work fine. Any advice would be appreciated.

az'03Silverado · August 25, 2004

It could be in the temp control unit on the dash. I'm not sure about the new vehicles but older ones were operated by the vacuum system. If there's a vacuum leak or a plugged vacuum line in the dash it could mess up the system. When the engine's off it will release the negative pressure and the system will go back to normal. I'm not sure, though, now to test the system. Maybe someone else will know more.

carguru · August 26, 2004

Nope, no vacuum used in these trucks. All electric actuators. You have either a bad actuator, broken/stuck temp door, or a bad control head. With the truck running and fan switch on lowest setting or off, do you hear a noise when you move the temp knob? If you hear a humming noise, this means the actuator should be working. It should operate for a few seconds. If not, your temp door may be binding. If no noise locate the temp actuator and probe the connector with a voltmeter. If you are getting full voltage from the control head, this could mean your actuator is bad or the door is broken/binding. Hope this helps.

carguru · August 26, 2004

Oh, BTW, the temp door actuator is located at the very bottom of the plenum near the center of the dash. It is shaped like a grand piano.

unlucky · August 26, 2004

Thanks, I will check for voltage at the actuator and report back.

unlucky · August 30, 2004

Ok, I have voltage to the actuator and it works fine until the heater has ran long enough to heat it up. Then the actuator wont function until I shut it off and let the water temp cool down. Looks like Im going to have to replace the actuator. Can anyone tell me how difficult this is going to be? STEALER wants big $$$...

carguru · August 30, 2004

Should be 2 screws holding the actuator on. Just unplug, and remove the 2 screws, should pull straight out. When it is hot, does the actuator still sound like it is running? It sounds like the output gear of the actuator and the cast pieces has worn. If you are mechanically inclined, you can open the actuator up and check the output gear. Good luck.

n8huntsman · February 21, 2006

I'm having the exact problem. What was the outcome?

Bish · February 21, 2006

I had the same problem and it was a bad actuator. IIRC it was around $30 online and tool about 5 minutes to replace. Once you drop the lower hush panel, the actuator cannot be missed and it installs very easily and completely solved the problem for me.

n8huntsman · February 21, 2006

I had the same problem and it was a bad actuator. IIRC it was around $30 online and tool about 5 minutes to replace. Once you drop the lower hush panel, the actuator cannot be missed and it installs very easily and completely solved the problem for me.

<{POST_SNAPBACK}>

You dont happen to have the part number so I can order it from gmpartsdirect do you?

00Tahoe · February 21, 2006

I had the same problem. What is happening is where the actuator is located, the heat from the heater is causing the plastic and the guides inside that hold the gears in place to expand. Therefore causing a binding. When you cut the car off and let it sit for a little bit, you allowed everything to cool down and contract back again. A friend of mine and I took out my actuator and lightly sanded down the the little metal guides holding the gears to make them just a teeny bit smaller and added some grease for good measure. Voila, no more problems.

Bish · February 21, 2006

I had the same problem and it was a bad actuator. IIRC it was around $30 online and tool about 5 minutes to replace. Once you drop the lower hush panel, the actuator cannot be missed and it installs very easily and completely solved the problem for me.

<{POST_SNAPBACK}>

You dont happen to have the part number so I can order it from gmpartsdirect do you?

<{POST_SNAPBACK}>

I usually buy from P&G at Partszone I use Contact Us to shoot them an email and thye usually respond with a part number within a day and then I order it from their website. Their shipping is a little better than GMpartsdirect.

I'll check tonight to see if I still have the receipt.

n8huntsman · February 22, 2006

I usually buy from P&G at Partszone I use Contact Us to shoot them an email and thye usually respond with a part number within a day and then I order it from their website. Their shipping is a little better than GMpartsdirect.

I'll check tonight to see if I still have the receipt.

<{POST_SNAPBACK}>

Its ok. The P/N is actually written on the actuator. I picked up a new one from the dealer for $62.00. The number for anyone looking is 52474810. I plugged it in and it initialized. Turned full cold and it went full cold. Turned full hot, and it went full hot. Then I turned it back again and nothing. Sticks on hot. And the actuator was still cold. I dont think that I boght it for nothing though. I think I was having more than one problem because initially it would only stick on hot after it got hot and I could turn the truck off and it would reset. I think that was the actuator. Then one day it just started sticking on full hot all the time.

Any ideas on what might be wrong now? Im thinking its the control unit. Anybody ever had one of these go out?

n8huntsman · February 23, 2006

I bought the new controls because whether it was the problem or not I needed a new one because my fan selector knob was broken off. Plugged it in and I still have the same problem. Is there a relay or fuse or something that I can check? I still cant get the stupid thing off of hot. Maybe the new actuator is no good too? I'm stumped. Anyone got any ideas?

chris_kucia · February 23, 2006

I bought the new controls because weather it was the problem or not I needed a new one because my fan selector knob was broken off. Plugged it in and I still have the same problem. Is there a relay or fuse or something that I can check? I still cant get the stupid thing off of hot. Maybe the new actuator is no good too? I'm stumped. Anyone got any ideas?

<{POST_SNAPBACK}>

Do you have the P/N for the controls?

I had the same problem. Replaced the actuator and its stuck on hot again.

However, the problem with my old actuator was that when it goes to full-hot, it actually goes past the point where it should to where the motor overtorques all the gears in the unit and jambs the mechanism.

I thought that the internal optical sensor that monitors the movement of the gears was malfunctioning. Now I believe its my control head.

In any event, even if you replace the control, if your gears are all bound up, the actuator isn't going to move until you unjamb the mechanism.

I would (very carefully) take the module apart. Look carefully at the gears to figure out which way the motor has to turn to unbind the assembly. Then either stick your finger in there and back up the motor, or gently pull the motor out and manually rotate all the gears back to full cold. Put it back together and see if it works.

I'm not positive about this, but I would be reluctant to just pull the "big gear" out and rotate it, since its directly connected to the little (blue, IIRC) gear that is the optical sensor. The relationship between those two might be important to preserve. Better to keep all the gears in place and either move the worm gear on the motor, or the gear the motor gear moves. The motor is not a step-motor, so you can rotate it as much as you want without worrying about throwing off the gear alignment, as long as all the other gears are intact.