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post #1 of (permalink) Old 12-10-2007, 06:53 PM Thread Starter
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88 YJ Heating Question.

Sorry in advance if this has been brought up before, I did a quick search and didnt come up with anything

I have an 88 YJ with the stock 4.2 and 5 speed. When I turn the heat on, there are three settings on the first slide lever. Defrost, Heat and Vent.
Below the Vent lever is the Hot, Cold Lever and to the left of them both is the Fan speed selector. If I turn the fan speed to any setting with the Hot/cold lever in any postition (makes no difference) And I slide the lever from off to defrost it blows out by the wind shield...fine. Slide it to the heat position and it blows out near the floor...perfectly fine. Slide it over to the vent position and the fan motor turns off. Now I looked all over and knoticed that the "vent position" does indeed open a vent on the passenger side. A large vent all the way to the right. Anyone know why the fan turns off? seems kind of odd.

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post #2 of (permalink) Old 12-11-2007, 08:50 AM
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That's an easy one to answer. The flap that opens on the passenger side that you see changes the flow of air from going through the heater box to dumping out inside. That flap is just before the blower motor and blocks the airflow to it.

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post #3 of (permalink) Old 12-11-2007, 09:50 AM
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But the problem with a YJ is that they don't have a mechanical controlled blend door like the CJ, it's a combination of mechanical and vacuum acutation.
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post #4 of (permalink) Old 12-11-2007, 10:26 AM
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Originally Posted by LEVE View Post
But the problem with a YJ is that they don't have a mechanical controlled blend door like the CJ, it's a combination of mechanical and vacuum acutation.
I don't think that changed till 90 or so. My 88 is the same as my 79 CJ7.

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post #5 of (permalink) Old 12-11-2007, 10:10 PM Thread Starter
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Quote:
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That's an easy one to answer. The flap that opens on the passenger side that you see changes the flow of air from going through the heater box to dumping out inside. That flap is just before the blower motor and blocks the airflow to it.

Yes, but why would it shut the fan motor off in the vent position? It's not just blocking the flow...it's stopping the motor from running.

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post #6 of (permalink) Old 12-12-2007, 07:10 AM
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Quote:
That flap is just before the blower motor and blocks the airflow to it.
If no air can get to the blower, there's no point to running it. Without air flow the motor will overheat.

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post #7 of (permalink) Old 12-12-2007, 07:59 AM Thread Starter
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If no air can get to the blower, there's no point to running it. Without air flow the motor will overheat.
First and foremost, Hello Jim, been awhile...this wedding and my Job have had me very busy so I havent been on in awhile
Went out to check the Jeep this morning based on the answers I got and realized that in the vent position its not closing the vent...its opening it. And it is mechanical not vacuum. It is cable driven. my heat is rod's and cables.


this is a picture of the vent in question.
thanks for the help guys, I am removing my entire dash in a couple of weeks to rewire the ignition harness and (amongst other things) I want to fix and check everything while its out. Windshield wiper motor and linkage, harnesses, vacuum lines and motors and all that. Should I add this heat to my list or is it working properly? lol Anyone elses YJ do the same thing?

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post #8 of (permalink) Old 12-12-2007, 08:17 AM
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Send me an Email ([email protected]) and I'll email back an article on refurbishing that heater box.
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post #9 of (permalink) Old 12-12-2007, 08:47 AM
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It's working properly. Yes, the vent is opening and when that flap opens, it closes off air from continuing through the heater system. The fan is behind that flap and that flap blocks the air to the fan. The fan is supposed to turn off when the vent is open.

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post #10 of (permalink) Old 12-12-2007, 07:01 PM Thread Starter
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Thanks Will, I appreciate the help. and LEVE I will email you and if you could send that to me that would be great! I would still like to take it apart while the dash is out because it seems like its alot louder than it should be. I'm sure it could use an overhaul.

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