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2002 heat slow to warm up

Hunter3006

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Shippensburg, Pa
Year, Model & Trim Level
2002, Explorer, Limited
Good morning, I have a 2002 explorer 4.0 limited with dual zone heat, also rear heat. It takes a long time for the heat to come out the vents. I've done some research and investigating and narrowed to heat control valve, blend doors, or possibly a coolant system problem as I have a leak at the thermostat housing. I have the console partially apart and the heat controls pulled out of the dash. I can see the passenger side blend door actuator. When I work the passenger side temp control the actuator turns about a 1/4 turn. Is that normal or should it turn more? Also what controls the heat control valve? It doesn't seem to move. I've applied external vacuum to it and it moves. Thanks for any help.
 


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Mbrooks420

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First step is to fix your leaks. Without it you won’t hold proper pressure, and air can get in causing a bubble.

1/4 turn seems right.

Can also be a stuck open thermostat if the heat eventually gets to full hot.
 




mountaineer2004

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Yes, I had an open stuck thermostat in my 2000 Grand Marquis.
Only time it got warm was when idling, but never when moving.
If it were me, I'd replace the thermostat with a new OEM one to start.
 




Hunter3006

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First step is to fix your leaks. Without it you won’t hold proper pressure, and air can get in causing a bubble.

1/4 turn seems right.

Can also be a stuck open thermostat if the heat eventually gets to full hot.
Ok, I'll start with the leaks, and check the heat valve. I forgot to mention that back in the summer the passenger side air would blow hot air when on ac.
 




Hunter3006

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Ok, I done a little more trouble shooting. Both blend doors seem to be rotating ok, meaning they rotate a 1/4 turn when temp is changed. Also I pulled the heat control valve out. It's N/O, when vacuum is applied it closes. The problem I seem to have is that there is no vacuum in the control vacuum line. So which control activates the vacuum line and should the control valve be open or closed for max heat?
 




TechGuru

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First thing is look at the temp guage, is the engine at operating temp when you're not getting heat? Does it ever reach operating temp? If not it's the thermostat. Only buy a Motorcraft one.
 




Hunter3006

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First thing is look at the temp guage, is the engine at operating temp when you're not getting heat? Does it ever reach operating temp? If not it's the thermostat. Only buy a Motorcraft one.
Yes it does reach operating temp according to the temp gauge.
 




Hunter3006

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I pulled the heat control valve out. It's N/O, when vacuum is applied it closes. The problem I seem to have is that there is no vacuum in the control vacuum line. So which control activates the vacuum line and should the control valve be open or closed for max heat?
I had it on heat, AC, and AC Max. No vacuum.
 




Hunter3006

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Ok I now have heat again. I flush the coolant system as well as the heater core. I replaced the thermostat housing and thermostat as well as the bottom radiator hose. Problems I have is the vents I don't have any air flow through the dash vents and the heater valve never seems to move.
 




Mbrooks420

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Do you have a check engine light on? Sounds like you have a vacuum issue.
 




Hunter3006

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Do you have a check engine light on? Sounds like you have a vacuum issue.
No check engine light. I do believe I have a vacuum problem. I had the heater valve out and it works with external vacuum but I can't get it to work in the vehicle. Is there a vacuum module under the dash somewhere?
 




Hunter3006

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Do you have a check engine light on? Sounds like you have a vacuum issue.
Update while working on another issue I found my vacuum problem. It was a vacuum lines connector disconnected. once I connected it I now have control of the vents.

I still have not found the proper sequence of operation of the heater valve.
 




Mbrooks420

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Not much sequence to it. When heat is called for it changes states. I believe it’s blocked at atmosphere and opens to allow coolant under vacuum.
 




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