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Unread 11-26-2004, 09:45 PM   #1
Phant0m51
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Heater won't blow hot air.

I have a '95 Jeep Grand Cherokee Limited. I've had it for a little over 2 years, and it's never blown hot air. I have the ATC set to HI and it still won't. When I go out and start my jeep in the morning, the temp will go up to normal operating temp, but the air coming from the vents will be luke warm at best. If I start driving, the temp goes up a bit, but not enough to warm up the Jeep.

Right now the Thermostat in it is only 165*, but even when it had a 190* Thermostat it was still luke warm air.

Any suggestions?

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Unread 11-26-2004, 09:53 PM   #2
Meerkat
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First, go back to the 190* thermostat, you are only hurting your Jeep by running anything else (assuming it is not modified).
Second, check your blend door. It sounds like it isn't opening properly. That's how the ATC controls the air temperature, by blending hot and cold air. If it is stuck closed, only the cold air is allowed in (stuck or with a bad motor).
Third, see the FAQ in this forum about how to pull the codes from the ATC, then either let us know what they say, or interpret them yourself.

Let us know how it goes.

HTH
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Unread 11-26-2004, 10:03 PM   #3
Phant0m51
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I'll get the thermostat changed as soon as I can afford to (newlywed and my wife is between jobs. God I hate bills!)

I should have mentioned that I just followed the ATC error check from the FAQ before I posted this. It shows no error codes (if I did it correctly).

Here's what I did:

Held in the AC and Recirc buttons, and turned the temp knob to the right 1 click. Now it showed 00, so I hit the AC button, and the little stick figure showed up, but the code stayed at 00.

If this is incorrect, let me know and I'll do it properly.

Also, how do I check the blend door? Probably going to have to take the dash apart, right?
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Unread 11-26-2004, 10:11 PM   #4
mr_user
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Thermostats are very very cheap at the local parts store, and pretty easy too install as well. Do you have a Haynes manual? There is a nice write up about HVAC diagnostics.

Why did you go 165* in the first place?
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Unread 11-26-2004, 10:14 PM   #5
Phant0m51
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What I mean by very little money is that I can't even buy lunch for work because of medical bills coming in. We're scraping at the bottom of the barrel. A Thermostat isn't very expensive, I know, but I'd also have to buy some coolant because of the cold weather now, I can't put just water in there. It's also really messy to change it out.

I originally changed it out because my jeep was overheating. Not really overheating, but with the AC on, it would get to 220 degrees. Wouldn't go any higher, but I didn't like it sitting there. Funny thing is, is that when I changed the thermostat, it still did it, I just never changed it back.

Oh, and the reason I changed it to the 165* is because the idiot at Pep boys told me to.

*edit* I asked the guy at pep boys for a 185*, and he told me they didn't carry those.
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Unread 11-26-2004, 10:43 PM   #6
Meerkat
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Phantom, you performed the steps, just fine. The lack of trouble codes bothers me. It could be the motor for the blend door is ok, but the gear is stripped, or somesuch.
You are right, the dash has to be disassembled to get to the blend door.

I do have another thing to check before you take your Jeep apart. After the engine has warmed up, turn the heater on maximum heat, then feel the two heater hoses under the hood. They should both be hot. If one is hot and the other cool, there is a blockage in the heater core. If both are hot, we are back to the blend door being the problem.

HTH
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Unread 11-26-2004, 10:46 PM   #7
Phant0m51
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Heh, I guess I could go do that right now. It's almost 11, but I wanna figure this out tonight.

I'll post back in about 15 minutes when the car is warmed up.
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Unread 11-26-2004, 10:52 PM   #8
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ah warren, you mentioned the inlet/outlet hoses from the heater core. made me think my wife had the same prob with her acura. i changed the thermostat and still had the prob, so i checked every hose for heat. the outlet hose would be cold while the inlet would be hot. so i checked every inch of the outlet hose and found a slit in it just large enough to allow an air blockage, therefore not allowing the radiator fluid to flow correctly, which caused overheating and the heater not heating up very much. very inexpensive replacement hose.
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Unread 11-26-2004, 10:57 PM   #9
Meerkat
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It's amazing all the different ways our vehicles find to mess with us, isn't it?
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Unread 11-26-2004, 11:04 PM   #10
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you are right warren, but with everyone's past experiences and knowledge, we can just about solve any prob fairly quickly. that's why i fell in love with this forum: the knowledge and friendly people.
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Unread 11-26-2004, 11:11 PM   #11
Meerkat
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I am definitely addicted to it!
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Unread 11-26-2004, 11:12 PM   #12
Phant0m51
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Ok, jeep warmed up and the heater core hoses seem fine. One was hot, the other was warm. Neither had any pressure, and both were warm across the entire tube (to make sure they didn't get warm from excess engine heat in certain areas).

So I guess I'll be tearing apart my dash one of these days and looking for the blend motor. Do you think the easiest way to diagnose this would be to switch between cold and warm temperatures to see if the arm moves? And while I'm down there, I'll take hold of the Heater core, just to make sure that it is warm, and I wasn't imagining the hoses being warm.
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Unread 11-26-2004, 11:26 PM   #13
Meerkat
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Such a shame it isn't going to be the "easy" fix.
When you get under there, you'll find the unit is pretty well sealed up and insulated. You aren't really going to be able to tell anything until you get it apart.

Let us know when you are ready to tackle it, and we'll post up some steps and pictures to help.

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Unread 12-02-2004, 07:07 PM   #14
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Ok, thought I'd bring this back from the dead because I got an error code today. But it was about 30 minutes after my jeep had been running. I started it, let it warm up for 20 minutes (18 degrees with a heater that only blows warm air really sucks). I drove to work, a 10 minute drive. Just before I got to work, I saw the 'Hi' on the temperature guage switch to 'Er'. After a few seconds, it went back. I got to work, checked for a code. Code# 51

"51......... CPU was in error.............................Calibration and CPU Data" from the FAQ. Does this mean I'm going to need a new conroller?
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Unread 12-11-2009, 04:57 PM   #15
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my gc 01 lmtd 4x4 is doing the same thing, but I do not get any warm air at least. Probably the only time that I will get some warm air is when the weather outside is pretty warm. It started doing this when I changed the blower resistor. Prior to this, the blower was blowing any air....the dodge dealer suggested I use the a kit because it would save me a lot of time. However, right after that was replaced, it stopped blowing warm air. Research and mechanics suggest that I dismantle the dash and change blend doors because these blend doors are now made of plastic and break easily. This was done so that the doors would break when getting stuck intead of forcing its motor and burning down. I am not sure whether I should do the dash work myself or take in to a shop. Does any body have any recommendations, ideas, numbers, etc. Thanx I appreciate the input.
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