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Unread 01-05-2010, 06:45 PM   #1
fstfl
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1994 YJ Wrangler 
 
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Cold, cold, cold air blowing when the heat is on

Here's the deal. I have a 1994 with a 4cyl. When I put the heat on the air ducts blow strait up cold air. The windshield seems to trickle heat. Any ideas as to how to fix this? Thermostat, heatercore? Help!

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Unread 01-05-2010, 06:49 PM   #2
Mean Max
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Are you sure you're not moving the switch all the way to the right, which is the "VENT" position?


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No one here knows what they are talking about. You should try Pirate 4x4 they will be happy to help you.

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Unread 01-05-2010, 06:50 PM   #3
Fenix85182
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First and foremost check the temperature of the engine after warm-up. If it is overheating (which I suspect it is), wait for cool down and check the antifreeze level. It is common that it will leak out enough antifreeze that the engine overheats and not enough fluid is pushed into the heater core for the air in the cab to warm up.
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Unread 01-05-2010, 06:51 PM   #4
Mean Max
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Are you sure you're getting full travel on the blend door linkage?

Here is the blend door linkage in the "COLD" position.


Here is the blend door linkage in the "HOT" position.


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Unread 01-05-2010, 06:52 PM   #5
Fenix85182
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Oh yeah, another thing to check--seen in Mean Max's picture, there is a slider on the right around where the passenger's knees would be. Make sure the slider has the metal rod in it (which controls the heated air/cool air ratio).
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Unread 01-05-2010, 06:56 PM   #6
tippmann243
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make sure all you linkages are working profperly

couple vents on mine got stuck open. i could turn the heat on and get hot air at idle, but once i was moving the cold air comming in the fresh air vents over took the heater and i began to get cold again.

pulled on the cable next to the passenger foot well and everything snapped closed. now i have to crack a window or i will melt it gets so hot inside
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Unread 12-02-2010, 10:00 AM   #7
martinrof
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I have a 94 wrangler yj that only blows cold air when the heater is on. I was told that if I changed out the thermostat, it would fix the problem, that the thermostst was stuck in the open position. Can anyone tell me if this is true and what can I do to fix the problem.
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Unread 12-02-2010, 11:12 AM   #8
sampsonite987
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Originally Posted by martinrof View Post
I have a 94 wrangler yj that only blows cold air when the heater is on. I was told that if I changed out the thermostat, it would fix the problem, that the thermostst was stuck in the open position. Can anyone tell me if this is true and what can I do to fix the problem.
If your thermostat is stuck open then it will take a looooong time for the engine to warm up to optimal operating temp in cold weather. Same thing happened in my wife's YJ. You would have to drive 15 miles in winter before you had heat. Replaced the t-stat, fixed it.

Like Fenix said, look at your temp gauge, but don't just check for it overheating. If the engine is not up to optimal temp after 10 or 15 minutes then replace the t-stat.
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Unread 12-02-2010, 11:43 AM   #9
muddy93
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There is also a "vent door" under the cowl vent.
mine got stuck open, and I was getting so much cold air coming in, that the heater could not keep up.

There are actually two doors under the cowl vent, one is cable actuated, and one is vacuum actuated, one is for the heat, and one is for the vent, but I don't remember which is which.
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Unread 12-02-2010, 12:08 PM   #10
Que89YJ
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In the FAQ there is a great list call all thing heating and cooling. Here is the link:
http://www.jeepforum.com/forum/f12/y...6/#post8107902
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