AC/Heat question

This morning driving to school I turned on the heat. I was freezing, and usually it gets hot pretty fast. But, when I had it on the "heat" setting, there wasn't hardly any air blowing out. I got more air coming out through the "vent" setting. Though the heat setting was warmer, I left it on the vent setting because at least something was coming out. It seems like with the heat one, heat is only on your feet, and not blowing out the other vents towards you. I haven't used the heat that much, but is this normal, or do you guys think something is wrong??? Also, I did have the temp. set to the hottest point (the far right). The AC works great, but I'm not so sure about the heat now... : /

(Sorry to bother, again...)

Was the cooling system drained recently?

The cooling system can have lots of air in it after its been drained and refilled, the air can get into the heater core and then no heat.

The pressure cap on the radiator should have a little valve in it, that draws back coolant from the reservour when the cooling system cools off and contracts. If the valve in the pressure cap is bad, or the tube or the reservour, it will suck air back into the system, instead of coolant.

There is also a valve in the hoses to the heater core that opens and closes when you turn on/off the heat. There is a vacuum line to the valve to operate it. If that valve is broken or the vacuum line disconnected the valve would not direct hot coolant to the heater core.

When I bought the Jeep, I'm pretty sure the guy said that he just had the cooling system drained pretty recently (but don't quote me on that...) I'll have to take a look at that, but how can you tell if the pressure cap is "bad?"

Well, you can go thru lots of trouble trying to get it tested, or you can do like I do. Its a critical piece to keep the engine cooled properly, they do go bad, but only cost like $6, so every couple of year I buy a new one and replace the old one. That way I never have a pressure cap problem. I do the same with the thermostat.

When the Engine is cool, open the pressure cap, if the level of coolant is below the top of the radiator, there is air in the cooling system.

There should be coolant all the way to the tipy top of the radiator, no air whatsoever.

Something is wrong with the coolant recovery system, that sucks coolant back in as the cooling system cools offs and contracts. Look over the entire route for the coolant to be sucked back in, remember as the fluid contracts it creates a vacuum that sucks the fluid back in, so look for anything that would leak that vacuum. The little valve in the pressure cap could be bad.

Alright. Thanks for the advice. I'll check it out today at lunch probably.

TIme to loose some of your noobiesness Hows' your tool skills ?
Parts store, 2 gallons of Prestone Anti-freeze, Prestone 7 hour flush.
Grocery store, 2 gallons of Distilled water [not spring water...DISTILLED]
Dealer, pressure cap

Drain cooling system into container and dispose of properly
Refill with water and add the Prestone flush, go drive it for the 7 hours.
Drain the water/cleaner out.
At this point it's a good idea to remove the two hoses that go to the heater core and using the garden hose alternately push water thru the heater core, first one way then the other till all the black gunk stops coming out. Disconnect them up by the front of the motor.
Reconnect the hoses, dump 1 gallon of Prestone in the radiator, then add one gallon of distilled water, dump half of the other gallon of prestone in the empty prestone jug and then use the remaining gallon of distilled water to top of the two half filled containers, result is two 50/50 mix containers of coolant. Now remove the overflow bottle and clean it out good then put it back in, refill the overflow bottle about half way with the 50/50 mix. Start the engine and start topping off the radiator, each time the thermostat opens the level will go down. As you top it off the coolant will look like green fizzy soda, thats air escaping. Each time you add cold coolant the thermostat will close, be patient, when it opens and pulls the level down add coolant. Once it stops pulling coolant down put the cap on, TIGHT. The rest of the air will bleed out thru the overlfow bottle over a few days.
Now in case I missed something the other reason you may not have heat is the fan, does the fan work ? low, med and high or just high speed ? if it only works on high speed then you need to replace the fan motor resistor pack, 10 min job.

The fan or "vent" setting that I was using this morning works on hi, med, and low, from what I know. I had it on medium this morning. So, I'm pretty sure the fan works. Thanks for the intructions/tips. If I need to do that, I'm sure my dad and I could handle it. Thanks for all the help/suggestions everyone!

I think you have a vacuum leak.

The heater controls use vacuum to operate the flappers to direct air to the defrost vents (top of dash), face-level vents (front of dash), or feet (under dash). The default position for the flappers is the defrost, so if you lose vacuum the air mostly gets directed out the defrost vents on the top of the dashboard. Next time you drive, put the fan on HI with the vent setting on either HEAT or VENT (not a/c or defrost) and then check to see where the air is actually blowing out of the vents.

Eagle said:

I think you have a vacuum leak.

The heater controls use vacuum to operate the flappers to direct air to the defrost vents (top of dash), face-level vents (front of dash), or feet (under dash). The default position for the flappers is the defrost, so if you lose vacuum the air mostly gets directed out the defrost vents on the top of the dashboard. Next time you drive, put the fan on HI with the vent setting on either HEAT or VENT (not a/c or defrost) and then check to see where the air is actually blowing out of the vents.

Click to expand...

I think it's probably a vacuum leak too. This morning again driving to school I tried it, and I can put it on low, med, and high, and no air blows out of all of the front vents, it only blows on your feet, which doesn't do yah much good. The defrost and vent settings seem to work fine though. It's just all of the front dash vents that don't work, and only for heat, because those vents work for every other setting... I'll have to look into this.

When my vent controls went bad, the vacuum leak was a vacuum tube that runs from the vacuum reservoir ("blimp") mounted to the right corner of the front bumper back to the firewall. The tube runs past the battery, and years of exposure to low-level acid fumes had eaten away the hose. I would suggest starting there. If the vacuum lines there are intact and healthy, then you may have to go into the dashboard and check that all the tubes connecting the controls to the various vacuum motors that run the dampers are intact and connected.

Do you by any chance have an aftermarket radio? The radio location is very tight, and if a ham-fisted installer shoved an aftermarket radio in there, it's possible that one or more of the vacuum tubes might have been knocked loose.

Yes, I have an after-factory radio. I'm curious, because the guy that previously owned this car was stereo crazy and had all kinds of wires coming from under the dash for his XM radio and iPod and what not. I took it to this local audio place and paid them to kind of reorganize all the wires and make sure everything was safe, because there was stuff everywhere! But anyway, my radio is actually kind of crooked in the space it's in, so it could have possibly been shoved in.

If I'm reading you correctly, you are saying that you are not getting heat through the dash vents. I can't speak for later years but at least through '93, with controls on the "heat" setting hot air comes out only through the floor vents. You should get some heated air through the dash vents on the "vent" setting with the temperature control at full heat (obviously a lot less warm air in this configuration in Colorado in winter than in East Texas any time).

If you are not getting any warm air through any vent setting, then you are back to the vacuum or heat control valve problem that others have detailed.

I APOLOGIZE!

Pelican is correct. Yes, when the control is set to the "HEAT" position, you should not have air blowing through the vents in the face of the dashboard, it should blow only on your feet.

And in the "VENT" position it blows only through the front of the dash, and not on the feet.

On the XJ, the "HI-LO" position only functions for air conditioning, not for heating. Don't ask me why, that's the way most vehicles did it back when the XJ was designed and they never changed it. So if that's the question, then the answer is "It's normal."

Really? That's odd. It seemed odd that on all the other settings stuff comes out the dash, but not heat. But if that's normal, okay. Thanks for all the help though.