No heat 96 Jeep Cherokee 4.0

[rockfarmer]

I have an issue with no heat in my Cherokee. (not needed most of the year in Texas, since its hot most of the year) But it would be nice when it does get cold.

The ac works fine, and air does come out of the floor vents when the heat is set to on, at the highest setting. I looked in the manual and didnt see anything about a fuse for this.

Not really excited about pulling apart a dash board for a heater core replacement. Things like that dont seem to go back together just right again. (but that might be explained by the 2 spare screws after its back together)

Am I missing something simple that I am supposed to switch under the hood? Any ideas would be really appreciated.

[Saudade]

With the engine hot and the heater on, carefully check the hoses going to the heater core. They should also be hot. If one is not, then you could have a clogged core or possibly a bad heater valve.

If they are both hot, you mght have a problem with the blend door that allows air to flow through the heater core. When the air temp control is moved to cold, the air is diverted around the core. When moved to hot, the door swings out of the way and allow air to enter the core.

[GregA]

Originally Posted by rockfarmer

Am I missing something simple that I am supposed to switch under the hood? Any ideas would be really appreciated.

Saudade is correct about feeling the hoses.

Also, the "switch under the hood" you asked about is the "heater valve" he referred to. You can see a picture of it here.

Another note: these valves are plastic & get brittle. When I had some work done on mine a few months ago, it broke apart and had to be replaced.

Oh yeah - its vacuum driven.

Take Care,

[rockfarmer]

Thanks for the info guys, that made it alot easier with the picture. The very bottom hose coming out of the heater valve was cold, and the other hose was labeled "heater" was warm.

I am not sure which would be the most likely candidate out of either the heater core or heater valve.

I might have to take it in to a pro if the instructions on autozone's site is correct. Draining all the coolant and ac refrigerant would be a pain.

[GregA]

Originally Posted by rockfarmer

Thanks for the info guys, that made it alot easier with the picture. The very bottom hose coming out of the heater valve was cold, and the other hose was labeled "heater" was warm.

I am not sure which would be the most likely candidate out of either the heater core or heater valve.

I might have to take it in to a pro if the instructions on autozone's site is correct. Draining all the coolant and ac refrigerant would be a pain.

I'm not sure WHY you would have to remove the AC refrigerant. Maybe because the compressor should be moved?

When my radiator was replaced, they did NOT have to discharge the AC - but they are "professionals" and do this stuff every day.

One other thing you might try, which I have suggested in another forum thread. CAREFULLY remove the hoses (2) that go between that control valve & the heater core AT that valve.

Then flush the core via those hoses using a garden hose. Flush it in both directions. If you see some "nasty" stuff come out during flushing, that is (or was) probably the problem.

Run the water through it until it runs clear & easy (same pressure out as in). Then reconnect the original hoses and try it again.

I figure it is worth a shot, but again - BE CAREFUL AND GENTAL around that valve. If it breaks you will be replacing it.

Take Care,

[Saudade]

Yeah, what Greg said. I'd remove the hoses from the core and try "back flushing" it. Easy on the pressure from the hose.

Also, you may need to be careful about allow any coolant to run into sewers or storm drains depending on where you live. Where I live in SoCal, the drains lead directly to the ocean so dumping coolant is a no-no.

[Panth3r25]

I am also having a problem with my heat. Ive checked the coolant level which was ok, I replaced the thermostat, and I checked the heater control valve but ended up replacing that as well. The blower is working. But when it idles its just cool air, when I accelerate it starts blowing warmer air. Both hoses get pretty hot also. If anyone can think of anything id appreciate it, its been getting pretty cold here lately. thanks

[fredjacksonsan]

That's a vacuum issue. At idle the vacuum is different than when you are on the gas. If you replace the vacuum tubing under the dash that should correct your problem.

[delonlemos]

Thanks for the info fredjacksonsan I will check my cherokee again

[thinmints]

Ill put my 2 cents in
my 96 xj was putting out Warm air but not like it was when she was new so i did what most have done and backed flushed the heater core except i filled my heater core with CLR and let it sit for about 30 minutes, then i just flushed it out with a water hose ( make sure you put the hose in an empty jug to get the used CLR) once it was running clear with the water i put all back together and now i can roast marshmallows from the heat