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My 1998 gmc jimmy slt has a heating problem. The heater wont turn off. As long as the car is on the heater is on full blast. The fans work and everything knob wise works but the heater is always on.

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  • GMC Master
  • 15,575 Answers

The air temperature valve electronic actuator positions the temperature door according to the temperature setting of the temperature control on the temperature control knob. For the full COLD temperature setting, the temperature control returns approximately 12 volts to the air temperature valve electric actuator. When the temperature setting is changed to full HOT, the temperature door is moved to the warm position and the output drops to about 0 volts. For a temperature setting in the mid range, the temperature door is positioned according to the voltage supplied through the temperature control switch.
Temperature Control Inoperative

2

Inspect the HVAC I fuse 21.
Is the fuse open?
--
Go to Step 20
Go to Step 3

3

  1. Disconnect the air temperature valve sensor.
  2. Turn the ignition switch to the RUN position.
  3. Move the headlamp switch to the PARK position.
  4. Using the J 35616-A , connect a J 39200 Digital Multimeter (DMM) between cavity 8 (CKT 733) of the air temperature valve motor connector and ground.
  5. Move the temperature control knob from the HOT position to the COLD position.
Does the voltage vary smoothly and continuously within the specified range?
0-12 V
Go to Step 4
Go to Step 9

4

Using the J 35616-A , connect a J 39200 DMM between cavity 10 (CKT 341) of the air temperature valve motor connector and ground.
Does the voltage equal the specified value?
B+
Go to Step 5
Go to Step 7

5

Using the J 35616-A , connect a J 39200 DMM between cavity 10 (CKT 341) and cavity 7 (CKT 1850) of the air temperature valve motor connector.
Does the voltage equal the specified value?
B+
Go to Step 6
Go to Step 8

6

Replace the air temperature valve motor.

Posted on Aug 31, 2015

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6ya6ya
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Posted on Jan 02, 2017

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WarHog
  • 9 Answers

SOURCE: 94 GMC Jimmy heater fan not working

if you hear the fans blowing and no heat is coming
then you mite have to replace the heater.

before you try to replace the heater talk to Lords

Posted on Dec 04, 2008

picatudo
  • 239 Answers

SOURCE: 2001 gmc jimmy defroster-heater blower will not direct heat

you have a vacuum leak

Posted on Jan 07, 2009

  • 73 Answers

SOURCE: 1998 GMC Jimmy-Turning Signal Noise

check all bulbs first

Posted on Apr 15, 2009

  • 1 Answer

SOURCE: 2001durango slt no heat in front

I have a 2001 Black Durango that had the same problem. There is a resister to the right of the ac/heat blower (underneath the dash on passaenger side). This needs to be replaced. You might want to replace the motor as well. Both are real easy. I had replaced the resister first and everthing worked fine for about 6 months and then my ac/heat would only works on high. I replaced the motor and now it works just fine. The resister was about $15 at dealership and the motor is prob around $40-$50. I hopes this helps. Good Luck!

Posted on Apr 22, 2009

  • 20 Answers

SOURCE: i have 2005 chevy trailblazer heater wont work,

Sounds like your water pump is going out or your thermostat is stuck. Check the thermostat first and make sure it is not frozen in the clsed position.

Posted on May 08, 2009

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