XJ Cherokee hvac issues, take 3

2000 Jeep Cherokee Sport 4x4.

So i think i may have stumbled across why my heat and a/c both suck bad on this thing inadvertently.

There's almost no resistance in the temperature control knob.

Also when i turn it from hot to cold, i can't hear anything moving in the dash. (I'm aware that it's electric) I ASSume i should be able to hear the blend door moving, yes?

Do the HVAC panels in these things go out? Am i maybe barking up the right tree finally? Heater core and blend door have both been replaced within the last 5 years.

I wouldn't be surprised. Take it apart and check it out, I bet it's got a shoddy connection somwhere.

The0retical wrote: Not sure if its the same but I had a Nissan whose fan resistor went out. It was basically a small card with 3 resistors for speeds locates behind the glove box. It did the same thing as what you are describing. I think it cost me 68 cents to replace from the local pick a part. Get a wiring schematic and it should show it between the knob and power supply.

Sorry.... i didn't describe the issue real well.

Fan works fine.

Heat is not hot. A/C is not cold.

In reply to The0retical:

Same thing I thought at first, then re-read it. The stupid resistors for the blower motors ALWAYS die on Jeeps. And the blend doors.

Please, don't even mention blend doors. I cringe that the cold weather is coming again and we will have several months of "flap, flap, flap, flap, flap" as the doors go back and forth while the heat is on.

Swank Force One wrote:

The0retical wrote: Not sure if its the same but I had a Nissan whose fan resistor went out. It was basically a small card with 3 resistors for speeds locates behind the glove box. It did the same thing as what you are describing. I think it cost me 68 cents to replace from the local pick a part. Get a wiring schematic and it should show it between the knob and power supply.

Sorry.... i didn't describe the issue real well. Fan works fine. Heat is not hot. A/C is not cold.

No you did I just wasn't reading for comprehension. then work beckoned and I left my lack of reading skills on full display when I lost my data connection.

But yes i should be able to hear the blend door move? Vehicle not running, but turned "on" so the blower and everything works. (In theory.)

+

Problem solved.

I'll let you do that after you buy me a new vehicle.

I guess i missed whatever thread this originally came up in.

This is super easy to figure out. Turn on car from dead cold (been sitting at least a few hours, preferably more) and turn on ac. Is ac cold when engine cold and gets warmer as engine warms up?

Vigo wrote: I guess i missed whatever thread this originally came up in. This is super easy to figure out. Turn on car from dead cold (been sitting at least a few hours, preferably more) and turn on ac. Is ac cold when engine cold and gets warmer as engine warms up?

It's been in a couple threads over the last almost 3 years. I had kinda just given up on it and figured it was easier to just listen to swmbo complain about the heat on cold days and the a/c on hot days than it was to actually figure out what was going on with it.

I'll test that, though...

Basically that would tell me that the blend door isn't doing anything at all, whether it's the door itself or the hvac controls is another story?

It would tell you whether there is a blend issue. The heater doesnt add any heat until the engine warms up, so the ac should function perfectly while the engine is cold if that is your ONLY problem. If it functions better, but not well, then you probably have more than one problem.

I somewhat doubt it'll work well either way at this point. I charged it 2 years ago and i think it leaks.

Do XJ's have an HVAC system check procedure? My WJ did, you pushed two buttons simoutaneously and turned a knob one click. Would cycle everything through the range and pop up an error code.

Blendorstore.com makes super solid kids. Redhookfern, that's what I used when I did mine in my Limited. Through-the-glovebox install. Took about 2 hours start to finish. Easy peasy with a hot knife.

Not sure. I really don't know anything about these things. Bought it almost 3 years ago. Haven't done anything to it but put gas, oil, front brakes, and 2 windshields on/in it.

http://www.xjjeeps.com/

Seems a little light on info compared to www.wjjeeps.com and www.wkjeeps.com though.

http://www.cherokeeforum.com/f2/heater-not-blowing-hot-ac-not-blowing-cold-73682/

^ says to check linkage

http://www.cherokeeforum.com/f51/hvac-operation-problems-37276/

I don't think it has a linkage. I'll have to double check.

Swank Force: The blend door motor can be removed from the passenger side footwell, just to the right of the center hump. It has 3 small screws if I remember correctly. And one plug to unplug. The space is a little tight.

If you turn the key to accesories and rotate the temperature knob from cold to hot and viceversa you should hear the blend door move, but it is faint and slow. You may have to get you ear next to it.

I had the same symptoms on my 99 and it was too separate issues. One is that it leaks freon so I have to put about two cans into it as hot weather starts every year. That solves the cold ac for me.

The heat was a blocked heater core, it had over a few years gotten cooler and cooler to non existent. I clamped both hoses coming out if the heater core on the passenger side firewall and then removed them and moved them out of the way. Then took my garden hose and turned it on about a 1/4 way where I had a stream but not too much pressure so as to blow the core.

Started by taking the hose end and putting in to the ends of the heater core sticking out of the firewall without blocking it completely, by changing from one to the other and increasing the pressure against the end it got all the rust and blockage off. Now heat works great and no leaks.

Good luck if it is something like this.

Thanks!

The heater core is relatively new, but coolant looked kinda gross last time i flushed it. I did the garden hose trick, but beyond some placebo effect, didn't seem to do a whole lot.

There's almost no resistance at all in the hot/cold knob when i turn it. Is this normal?

I don't drive it enough to know if it's always been like that or not. I drive it maybe once a month.

In reply to Swank Force One: The knob itself rotates very easily, softer than the fan speed etc. Since it controls the blend door by electric motor and not vacuum as older ones it does not need to push on much other than an electric contact.

The heater core tends to collect all the crap and rust from the system so even though it is new it may have gotten blocked. Run the jeep for a good while keeping the heat off (as it would cool the core) and see if the in and out hoses from the heater core feel the same temperature. If they do then the core is flowing well, if not then it is blocked partially or fully.