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Ok the heater Coil in my comanche is getting hot (it must be because the line going in and out are 140 deg.) I was thinking a door isnt opening or something. But i can hear a clicking or a slamming noise when i switch to heat my blower is fine.. this is getting on my nerves now. anyone have this problem and know how to fix it?

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There's a vacuum controlled valve on the hose to the heater core under the hood. If the vacuum line came off, the valve defaults to open.

 

But even if coolant is circulating through the heater core, unless the heater control is set to warm/hot, the air should not travel through it to het warmed up.

 

With the heater controls set to cold I have noticed no difference in cabin temperature between the valve being open (disconnected) and the valve being closed.

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Heater? It's 4 degrees here right now. You're in Florida, what do you need heat for! :fs1: . JK. So your fan works OK, You hear the blend door open all the way when you go to heat (that, by the way, is called the 'thud :D ' test. Technical term). How about air flow? When you move through Def, floor,blend,panel etc, does the air come out the proper vents?

 

When you have it on 'heat', feel the air flow velocity coming out on the floor, and change btwn hot and cold. The amount of air should not change. If it is reduced when you put it on 'hot', you may have something blocking the heater core. I have seen the foam come off of the doors and get stuck on the heater core restricting flow and causing low heat, or it could be an armadillo is living inside there :yes: .

 

I also think you should have more than 140 degrees at the core. With the truck fully warmed up, check the hoses. If they are at engine temp at the head and pump, and get colder as you go toward the firewall, you may have a plugged up core. Pull both hoses (afetr it cools of course :doh: ) and try to flush it out. Good luck and enjoy those chilly 60's and 70's down there :cheers:

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My heater has recently gone "lame" and only blows lukewarm air. It is close to 0º this morning and the temp gauge moves to about 200º after about 1.5 miles and then drops a little when the thermostat opens and then comes back up and stays at about 200º. The level of coolant in the plastic bottle is correct. Cap seals well.

 

It has the AC if that matters. The fan only works on high anymore.

 

I have not tested the temperature of the coolant with a different thermometer yet.

 

The location of the blow changes as I change the lever from defrost, heat, vent, etc. so I think that portion is working OK.

 

There is no change in the volume of air when I move the temperature lever from cold to hot and back.

 

Just where would the vacuum line be located that may be my problem?

 

Thanks in advance!

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The fan only works on high anymore.

 

 

That is usually an indication of a blown resistor pack. (when the resistors are blown, it generally leave HIGH as the only choice) It is located next to the passengers feet and looks like a little cover held to the air duct by a little screw or 2. Be careful though, as a dying blower motor has been known to pull too many amps and slowly kill the resistor pack, and if that's the case it'll eventually take out the new one too. I recommend getting a functioning resistor pack from the nearest pull a part junkyard for cheap and trying that. I do believe they are available at the dealerships still. :thumbsup:

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My heater has recently gone "lame" and only blows lukewarm air. It is close to 0º this morning and the temp gauge moves to about 200º after about 1.5 miles and then drops a little when the thermostat opens and then comes back up and stays at about 200º. The level of coolant in the plastic bottle is correct. Cap seals well.

 

It has the AC if that matters. The fan only works on high anymore.

 

I have not tested the temperature of the coolant with a different thermometer yet.

 

The location of the blow changes as I change the lever from defrost, heat, vent, etc. so I think that portion is working OK.

 

There is no change in the volume of air when I move the temperature lever from cold to hot and back.

 

Just where would the vacuum line be located that may be my problem?

 

Thanks in advance!

 

HOLY :hijack: BATMAN

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My heater has recently gone "lame" and only blows lukewarm air. It is close to 0º this morning and the temp gauge moves to about 200º after about 1.5 miles and then drops a little when the thermostat opens and then comes back up and stays at about 200º. The level of coolant in the plastic bottle is correct. Cap seals well.

 

It has the AC if that matters. The fan only works on high anymore.

 

I have not tested the temperature of the coolant with a different thermometer yet.

 

The location of the blow changes as I change the lever from defrost, heat, vent, etc. so I think that portion is working OK.

 

There is no change in the volume of air when I move the temperature lever from cold to hot and back.

 

Just where would the vacuum line be located that may be my problem?

 

Thanks in advance!

Check the plastic tube that runs across the passenger inner fender behind the battery. If you've had the battery out for any reason and werent careful that line is easily cracked or broken. don't ask me how I know. :doh:

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I saw that vaccum line. It opens and closes a door. Only opens when i turn the A/c on.

Ventalation is fine, i blows out the same amount of air through all the vents.

only thing i don't get is that The IN and OUT lines are boath around 140-180 degrees.

I don't see any coolant in my cab or anything leaking anywhere.

 

 

OhH and, Theres a small brittle I'm guessing vaccum line coming out of my A/C txv and my heater txv. and their both not connected to anything. so i think its meant to be connected. there both the same color etc.. Can someone look at their jeep and tell me. :hmm:

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txv....now there's a term not often uttered. You do refrigeration for a living ;) ?

 

Yes, those lines need to be connected (one should be pink and one black, but that's beside the point). There's a vaccuum operated valve that opens/closes the coolant supply to the heater core, and those lines control it. When you move the HVAC lever in the cab, not only does it send a vac signal to the plenum to direct air movement, it also sends a vac signal to that valve to open and circulate coolant thru the heater core (XJ/MJ only, YJ/TJ's don't have that and have constant flow thru the core).

 

Connect one of your lines to the vac line that comes from under the battery tray (mentioned earlier) to provide the vac signal, and the other line to the diapraghm on the heater control valve. Then you'll have circulation thru the heater core, and warmth ;)

 

Jeff

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yeah, I'm talking about under the hood too......right beside where the HVAC fan motor is, up on the firewall. There should be two hard plastic vac lines coming out of a foam-type recatangular block....they are the lines I'm refering to. They control the valve that lets coolant pass thru the heater core:

 

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One of those is the vacuum supply line that provides the vacuum source to the heater controls. It hooks up to the main vacuum line coming from the reservoir in the bumper. The other one goes to the valve that controls the coolant flow.

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Ok the heater Coil in my comanche is getting hot (it must be because the line going in and out are 140 deg.)

 

I would still flush out the heater core. I bet some trash has stopped up a few of the rails and still let enough fluid to get by and heat the lines.. I was having the same problem, then one day, I just though I'd give it a try. Its to easy to remove the heater lines and run some water though it. Worked for me, but I didnt get a temp on the lines they both just felt warm to the touch.

 

Maybe if there was a way to actully put your hand up on the heater core to see if its warm, or shoot it with a laser to get a temp..

Is there a way to actully check the temp of the heater core inside the box????? I don't know, but would be a good way to troubleshoot it.

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