Question about 1999 GMC Jimmy

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Vents blowing constant cold air...told it was the blend door on my 1999 GMC Jimmy ....replaced thermostat.....flushed system and replaced cracked radiator....heater coil is not leaking. A/C is a seperate unit, has its own switch and indicator light...that is not on.. I have NO heat...Freezing here in Michigan....HELP!!! Jay

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  • 1,201 Answers

JKS219, with a hot motor, feel the 2 coolant hoses coming out of the firewall. Both should be hot, if not, your heater core has blockage. The fix is, disconnect both hoses from the motor, connect garden hose to cold side and blow out the blockage into a empty cola liter jug. Run water until clear, then switch sides and do it again until runs clear. No cost repair if it's this.

Posted on Sep 19, 2017

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  • 33 Answers

Its more than likely the blend door not moving to the heat position. I'm not familiar with the location of the blend door in the 1999 GMC jimmy, since I'm not a mechanic and don't have a manual on that vehicle. If you can get to the blend door housing you might be able to move it physically.

Posted on Sep 13, 2017

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

you have a vacuum leak

Posted on Jan 07, 2009

  • 1 Answer

SOURCE: My 2000 GMC Jimmy has been blowing cold air. We

airjoc does not have a clue to your problem, I take you want to have warmer air not cooler ac. check the control system, if you have a vacum system tou may have a leak, if it is controlled by voltage, check the control panel and the control box. Also open the hood, place the heater on high but not on any defrost setting preferrably on just the floor setting. Start the engine and see if the ac compressor is running. If it is, the control panel is bad.

Posted on Oct 09, 2009

  • 173 Answers

SOURCE: No heat in 98 jimmy. Replaced water pump,

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

Posted on Dec 07, 2009

  • 173 Answers

SOURCE: Heat not working on 98 gmc jimmy. Replaced

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

Posted on Dec 07, 2009

  • 11800 Answers

SOURCE: 19996 Gmc Jimmy is leaking

There are 2 vents on the tank - one for the EVAP (its pipe goes to the front) and the one for the air venting (its pipe goes to the filler cap).
If by gas you mean vapours then the vent is doing its job - eliminating the excessive pressure in the tank. This pressure is caused by a blocked pipe in the EVAP system - one of the pipes you replaced is badly installed, redo all of them.
If by gas you are referring to liquid fuel then tank is overfilled and when the gasoline is heated it expands, completely fills the tank and escapes thru that vent which should have the pipe attached to it - siphon out some of the fuel and replace the vent then check the pipe leading to the cap.

Posted on Apr 27, 2011

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check the blend door motor under (behind) the glovebox. make sure the ac system is cooling first.

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