Heat only blows hot on high - JeepForum.com
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post #1 of 10 Old 10-24-2016, 02:33 PM Thread Starter
CarmineZJ
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Xj Heat only blows hot on high

So ive owned this jeep for a little over a year and dealt with the poor heat for a while. But now i want to fix it, i get heat in it when the jeeps up to running temp, defrosters, etc but it only blows out on high. I did a little looking around before posting here and found there is a relay that controls this that could be bad. Also it only blows hot even when the ac is on or on cold. What could my other problems be?


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post #2 of 10 Old 10-24-2016, 02:36 PM
Tru2Chevy
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Do you mean that the vents don't move any air unless the fan is set to high? If so, then the blower motor resistor is bad.

If you only get hot air from the vents all the time (even when it's cold outside) then it sounds like the door that controls airflow in the dash is stuck or broken. It's only allowing air to flow over the heater core and then into the cabin through whichever vents you have selected.

- Justin

1992 Cherokee Laredo - mostly stock, DD. 300k miles and counting

2004 Grand Cherokee Laredo - 4.7, bone stock - Wife's DD


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post #3 of 10 Old 10-24-2016, 02:39 PM Thread Starter
CarmineZJ
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Quote:
Originally Posted by Tru2Chevy View Post
Do you mean that the vents don't move any air unless the fan is set to high? If so, then the blower motor resistor is bad.

If you only get hot air from the vents all the time (even when it's cold outside) then it sounds like the door that controls airflow in the dash is stuck or broken. It's only allowing air to flow over the heater core and then into the cabin through whichever vents you have selected.

- Justin
yes

and that can be solved by removing the climate control switches its behind that panel right?

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post #4 of 10 Old 10-24-2016, 02:42 PM
Tru2Chevy
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I am not sure where the blower motor resistor is located on the XJ - I've never had to replace one. Your other issue will likely require disassembly of most of the dash to fix.

- Justin

1992 Cherokee Laredo - mostly stock, DD. 300k miles and counting

2004 Grand Cherokee Laredo - 4.7, bone stock - Wife's DD


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post #5 of 10 Old 10-24-2016, 02:50 PM Thread Starter
CarmineZJ
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Quote:
Originally Posted by Tru2Chevy View Post
I am not sure where the blower motor resistor is located on the XJ - I've never had to replace one. Your other issue will likely require disassembly of most of the dash to fix.

- Justin
ahh i was hoping i wasnt going to have to oh well

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post #6 of 10 Old 10-24-2016, 05:48 PM
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Hold on. You don't have to disassemble the dash to fix these issues.

First, the blower speed issue may be the Blower Resistor Block (as previously discussed) and second, not being able to control the heat/cold airflow maybe the Blend-Air Door actuator.

Study these diagrams. One is the blower circuit and the other is the Blend-Air Door circuit. Some tips below the diagrams.

Blend-Air Door circuit:


.
Blower circuit:


.
If, by selecting the blower speeds, other than HI (#4), the blower doesn't work but it works in HI, then it can be assumed the blower resistor block is bad (common issue).

You can access the blower resistor block by removing the kick panel under the glove box. See pic.

The kick panel attach screws in the drawing are misleading. The upper left screw is accessed by rolling the glove box down (remove the two rubber stops and let the glove box hang down). You have to hunt for it a bit, but the upper left screw can be seen. Just loosen the screw with an 8MM socket, it does not have to be removed. The upper right (in the pic) screw is a PITA. It's located up under the glove box area by the passenger courtesy light. You'll need a mirror to see it. Loosen it.

The lower left screw is easily seen, and must be removed. The lower left screw in the pic is also somewhat hidden. No mirror required but a flashlight is required to find it. Remove it.

Once the kick panel is off you can see the Blower Resistor Block. See pic.


.
The Blend-Air Door Actuator is located in the upper left corner of the passenger foot well.

Use a flashlight.

Position yourself so you can see the actuator (see pic on diagram). Select low speed on the blower speed switch, select any position of the mode selector switch (except OFF), turn the ignition switch to RUN/ON but don't start the engine. Rotate the temp control knob from full hot (Red) to full cold (blue) while looking at the bottom of the actuator. You should see the white motor intermediate drive shaft move from stop to stop (around 90 degrees movement each way.

If the actuator/motor does not move, remove the motor and bracket together by removing three screws. With the electrical connector attached, try rotating the temp control again. If it moves the Blend Air Door may be jammed inside the HVAC Unit. If it doesn't move the actuator may be shot.

If the actuator moves, try moving the Blend-Air Door shaft by hand. If it doesn't move, carefully try and turn the shaft using pliers. If it won't move, you have just been groped.

Note that the intermediate drive shaft has been know to get buggered up where it couples with the door shaft. Take a look.

Tell us what you see.
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post #7 of 10 Old 10-24-2016, 06:43 PM Thread Starter
CarmineZJ
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Quote:
Originally Posted by CCKen View Post
Hold on. You don't have to disassemble the dash to fix these issues.

First, the blower speed issue may be the Blower Resistor Block (as previously discussed) and second, not being able to control the heat/cold airflow maybe the Blend-Air Door actuator.

Study these diagrams. One is the blower circuit and the other is the Blend-Air Door circuit. Some tips below the diagrams.

Blend-Air Door circuit:


.
Blower circuit:


.
If, by selecting the blower speeds, other than HI (#4), the blower doesn't work but it works in HI, then it can be assumed the blower resistor block is bad (common issue).

You can access the blower resistor block by removing the kick panel under the glove box. See pic.

The kick panel attach screws in the drawing are misleading. The upper left screw is accessed by rolling the glove box down (remove the two rubber stops and let the glove box hang down). You have to hunt for it a bit, but the upper left screw can be seen. Just loosen the screw with an 8MM socket, it does not have to be removed. The upper (in the pic) screw is a PITA. It's located up under the glove box area by the passenger courtesy light. You'll need a mirror to see it. Loosen it.

The lower left screw is easily seen, and must be removed. The lower left screw in the pic is also somewhat hidden. No mirror required but a flashlight is required to find it. Remove it.

Once the kick panel is off you can see the Blower Resistor Block. See pic.


.
The Blend-Air Door Actuator is located in the upper left corner of the passenger foot well.

Use a flashlight.

Position yourself so you can see the actuator (see pic on diagram). Select low speed on the blower speed switch, select any position of the mode selector switch (except OFF), turn the ignition switch to RUN/ON but don't start the engine. Rotate the temp control knob from full hot (Red) to full cold (blue) while looking at the bottom of the actuator. You should see the white motor intermediate drive shaft move from stop to stop (around 90 degrees movement each way.

If the actuator/motor does not move, remove the motor and bracket together by removing three screws. With the electrical connector attached, try rotating the temp control again. If it moves the Blend Air Door may be jammed inside the HVAC Unit. If it doesn't move the actuator may be shot.

If the actuator moves, try moving the Blend-Air Door shaft by hand. If it doesn't move, carefully try and turn the shaft using pliers. If it won't move, you have just been groped.

Note that the intermediate drive shaft has been know to get buggered up where it couples with the door shaft. Take a look.

Tell us what you see.
thank you very helpful when i have some spare time ill try to mess around with this stuff.

Buy a jeep they said, it would be fun they said..

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post #8 of 10 Old 10-24-2016, 09:50 PM
Tru2Chevy
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Good info Ken, thanks.

- Justin

1992 Cherokee Laredo - mostly stock, DD. 300k miles and counting

2004 Grand Cherokee Laredo - 4.7, bone stock - Wife's DD


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post #9 of 10 Old 10-28-2016, 09:01 PM Thread Starter
CarmineZJ
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well I finally got some spare time today and got to mess with this stuff. swapped out the bmr and now it works great. looking at the blend door actuator it had some kind of goop on it and when i tried to test it i didnt see any movement and could quite find the best way to get the screwdriver in to pull it out, also had to go to work. all in all a good day just need to find some patience to put the kick panel back on

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post #10 of 10 Old 10-29-2016, 06:28 AM
CCKen
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Quote:
Originally Posted by CarmineZJ View Post
well I finally got some spare time today and got to mess with this stuff. swapped out the bmr and now it works great. looking at the blend door actuator it had some kind of goop on it and when i tried to test it i didnt see any movement and could quite find the best way to get the screwdriver in to pull it out, also had to go to work. all in all a good day just need to find some patience to put the kick panel back on
You need to remove the three attach screws with a socket to remove the bracket/motor assembly then the three screws to remove the motor.

Sounds like the actuator motor is toast.

Dorman sells the motor, Mopar part number 5013741AA.

http://www.rockauto.com/en/partsearc...ng.com+URL+%2F
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