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1999 gmc jimmy cant get heat, heater core fine, can get heat on floor but nothing when switch to vent. can see actuators working. ambient temp sensors resistance on 1 one passenger side no resistance
Re: 1999 gmc jimmy cant get heat, heater core fine, can...
Just went through the same thing in my 99 silverado.could see acctuators working also,but i still had to change" mode" acctuator as it was only operating on 2 modes not all 5
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I think it is the actuator/solenoid that is in the middle of the dash at the very bottom of the hvac case (against floorboard). You may have to remove the long plastic cover held in by 7mm screws. The actuator is held in with 5.5mm screws I think. You can remove this and turn it by hand and see if it changes anything.
is the climate control switching over like from floor to defrost to vent ? maybe the flap door not working in heater box.both hoses are hot but is water flowing thru heater core.
Could be that the heater core is disconnected, there are two hoses that attach to the heather core that come out of the engine, this provides hot water to the core thus making the heater work, when the heater core starts leaking water the quick and fast fix would be to bypass the heater core and connect the two hoses together, check under the hood on the left passenger side there should be two hoses about 1" thick see if there are connected together or of they seem to be connected to 2 outlets that come out of the inside of the vehicle. people do that specially if selling vehicle.
Possibly.. the actuators which operate the doors actually have a position signal for reference, but the actual motors inside the actuators dont realize there is a limit and overshoot their limits causing the fine wires inside to rip apart rendering the actuator scrap but this happens when actuators are still plugged in to the connector while being taken off the heater door, and they can and will still move with the key in the off position if the actuator thinks it not in the proper position..thats how they work anyway.hope you had them unplugged untill the last, then this would'nt happen....hope this explaination helped
Flushing the heater core is fairly easy just remove the 2 hoses going to the heater core and use a different hose if you have to and use a garden hose to backflush the blockage out..this may take as much as 5-6 times also check for vacumn lines missing or disconnected or breaks pinched ect... some where in the vicinity of the passenger side under hood by the a/c lines ect. good luck hope this helps
Your going to have to replace the switch. The switch it self may have gone bad, since it works on a vacuum. It's common for the diaphragm in the switch assembly to go bad, if it's not the switch. Then it's going to be a bad actuator door and will need to be freed up. I have found it to be the switch it self get dirty and the vacuum needed to activate the actuator door is not there.
Good luck and keep me posted. When you turn the switch from defrost to heater, do you hear a air leak??? If you do then it's a good chance that it's the switch it self.
There is a actuator on the right side of your leg while sitting in the drivers seat under the dash. It has a plastic rod for actuation manually actuate this diverter and should be the problem.
We had the same problem in our 98 GMC Jimmy. Was blowing hot air everywher with everything shut off & air conditioning would not work. We found out it was the Blend Dood Actuator, it is located behind the glovebox. We purchased one on EBay & replaced it and are back on track again. Good luck!
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