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yet another heater temp control problem....

Discussion in 'General Chevy & GM Tech Questions' started by jeepster, Dec 16, 2008.

  1. jeepster

    jeepster New Member

    Okay, this is my first post, but have tried to familiarize myself with the site. I searched around a bit to find some useful info.

    Here is my situation. Last summer I notced that if I shut my truck off with the heat on then returned and tried to turn on the A/C, I would have to turn the truck off, turn the temp to cold, then restart truck. This worked to get the cold a/c on. Never had any trouble with the heat until now.

    I basically have no temperature controls at all now. The truck warms up to 210 with no issues and I have plenty of antifreeze. I noticed that my feet were cold despite having the floor/defrost on. I turned it to the vents and it was blowing cool air. The air does not change temp at all despite temp switch position (even with a/c on) when the fan is blowing full blast. I then noticed that if I turned the fan down to 1 it would get a little warmer. I can hear some action taking place when I turn the temp control, but it makes no difference in air temp.

    I searched around and found these threads, Which were somewhat helpful.
    http://www.gmtruckclub.com/forum/showthread.php?t=16703&highlight=heater
    http://www.gmtruckclub.com/forum/showthread.php?t=16756&highlight=heater

    The question I have is what part is likely bad, and how hard is it to change. Is it part 18, 22, 21 or?? in this schematic? www.gmpartsclub.com

    I am leaving for a 3000 mile round trip through the northern US in three days so I need this heat working. Thanks in advance and I hope this has not been answered a million times. Truck has manual controls and the 4.8L engine (the small v-8). Very basic work truck.
  2. jeepster

    jeepster New Member

    so I tried my own links, and the parts direct needs all the info put in again. Anyway, the parts I am pertaining to are the actuator temp, the actuator mode, and the valve temperature. Which is the likely culprit.

    truck is a 2000 silverado, 5 speed, new body, vinyl floors, manual windows, work truck.
  3. daddytech

    daddytech New Member

    I looked at it myself using your link for a 2000 Chevrolet 1500 and it looks like part number 5 or 6 if it's the older style 2000 like my tahoe if it's the newer style i would look at part # 16 or 18. check to make sure there isn't a stripped gear or broken cable end or a broken piece out of the lever end that switches it back and forth. some times it's something as simple as the cable slipping out of the end of the control arm (part number 20 if what isn't working is number 16 part number 24 if it's for door number 18).
  4. jeepster

    jeepster New Member

    i looked over the chematic again and played with the truck. I still have control over cabin air vs. external air. I can hear that flap #16 moving and it changes the sound and way the air comes into the cabin like normal. I am inclined to think that it is related to door number 18 at this point. I wil be tearing into it today.

    Does anyone know how fast www.gmpartsclub.com direct ships?
  5. jeepster

    jeepster New Member

    okay, the actuator is very slow and weak. the door was also stuck, so I used some pliers and manage to free it without disassembling the heater. Manually turned it to full hot reinstalled the actuator and viola>>>>>HEAT!

    Then today, I was driving and same thing was warm then went cold and cannot cange temperature. I did the same thing as yesterday, but the flap was already turned to full hot. I got out and checked the heat core hoses. One side is hot and the other is luke warm. Is this normal?

    I squeezed and massaged the radiator lines and heater core lines and then the air got hotter again. I dont know if this was due to the truck running stationary for 15 min or if there is some air in the lines. The reserve tank is full. Anyone have any ideas?
  6. BzGmTech

    BzGmTech New Member

    I have seen the air temp actuators on the 1999 to 2002 trucks get weak, when the blower motor is above speed #3 it can't pull past the force of the blower.

    gmpartsdirec t ships slow and the shipping is expensive, try www.gmpartsclub.com
  7. jeepster

    jeepster New Member

    that could easilyt be the problem. Today, I returned it to the hottest position by hand and have the actuator disconnected. it has been hot air all day today. Ill test it out tomorrow on my long journey through Montana.
  8. jeepster

    jeepster New Member

    I have still not changed the actuator, but I have solved the heat problem. It was just an old fashioned air lock in the heater core. I disconnected the return heater line and it was bone dry. I added almost 40 OZ of antifreeze directly into the line. I was then able to start the truck and massage the lines which yielded a lot of bubbles in the overflow tank. The return line then became hot and I was blessed with warm air in the cab despite the -13 degree temps here in central Montana. Thanks for all the info guys.
  9. daddytech

    daddytech New Member

    I kinda wondered if it wasn't air in the line somewhere when ever you decide to change it out or flush out the system then make sure the front end is up on a lift or ramps when you do the refil and run it while you are filling it and you shouldn't have that problem again.

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