Ok, so first cool day came about two weeks ago so I needed the heater to defrost the windshield. Worked great. Two weeks later it gets cool enough to use the heater once more except this time no heat. I did notice that after the first time using it that my AC didn't want to blow cold at first. I had to crank it on max AC for a little but to get the AC to blow cold again. I have changed the resistor and the AC relay. Any suggestions would help because I am lost when it comes to the AC/Heat.

 

I would start by back flushing you heater core keep flushing the core in both directions several times and once you think it's well flushed, flush it some more. Also make sure that you blend door is operating correctly when you change the settings.

 

I do not know how to flush the heater core or where the blend door is. I will look in my Haynes Manuel for some advice.

 

Firewall under the hood, right side two heater lines going in. Take the lines off and flush through the core as suggested above. It's pretty simple.

Black89

 

Bad thermostat or low antifreeze

 

Is there a way to flush the condenser without discharging the AC system? Haynes manual says to discharge system which means I'd have to charge it again and that crap ain't cheap.

 

Your not flushing the condenser. Your doing the heater core. The AC system if you were to do anything would be pulled down under vac. and tested for leaks. Then simply recharged.

Black89

 

I have a 88 jeep sport and my heater seems to not work well at all
It seems like there no heat and just blows air
Also when I turn my **** all the way on high the heat shuts off why

 

I had the same problem with it shutting off on high. I would first change the relay that is behind the glove box if your model has that. If not I would change the resistor for sure. That cured my problem with the max AC setting. I'm still trying to figure out why I have no heat.

 

With the engine warmed up and idling, feel the heater hoses near the heater core. Are they warm/hot?

 

Good point if the Heater core is good both input and output line will be hot. If only one is hot then your heater core is plugged and or getting plugged up. Your best bet is to just pop the lines off and flush it out for a while with the garden hose on high. try to blast the crap out.

Black89

 

there is a vacuum valve inline on the heater hoses, I'd check there first. maybe the vacuum hose came off. Also that is a mighty relic you have there I would suggest you get a repair book, it will help with the more basic stuff. They're cheap and full of knowledge.

Bird

 

Does your blower work on all four settings?

Your blend-air door is electrically operated. You can check the operation of the door visually. Refer to the below pic.

Look under the passenger side dash, beyond the passenger floor air outlet,and you'll see the blend-air door actuator motor.

To check its operation look at the white intermediate drive shaft were it protrudes through the bottom of the actuator mounting bracket. Turn the ignition switch to RUN (engine not started), then move the temperature control **** on the Heat/AC control panel from Blue to Red and back. The intermediate drive shaft should move approximate 90 degrees from stop-to-stop. If it doesn't move at all the motor may be burned out or the blend-air door is stuck. To check, remove the actuator assembly from the bottom of the HVAC unit (couple of screws) and reconnect the motor electrical connector, and try running it through again. If the actutor works the door is stuck, if it still won't move the motor may be burned up (common fault).

Or the Blend-Air Door motor is not getting power for some reason. To check you must remove the connector from the motor and check for voltage at pin cavity 10 on the connector with the Ignition Switch to RUN, using a voltage probe or a voltmeter. If fuse F25 in the Junction Block is blown, the blower won't work.

If it appears the Blend-Air Door is stuck you can try moving the door shaft (actuator removed) using pliers. If it won't move, or is very stiff, there is little you can do to fix the door except to remove the HVAC unit and disassemble it to replace the door.

If all the above checks prove the Blend-Air Door system functions normally, there's obviously something else wrong in your system.

Let us know what you find.

 

I will try what you wrote as soon as my jeep gets back from the bodyshop. Got in a wreck today. Hopefully won't take long. But thank you for the in depth explanation. Thanks you!

 

Thanks everyone for the advice. And I will try it if I ever get the chance again. I was notified today that my Cherokee is going to be totaled. I guess I can always buy another one with the ins money. We shall see. Maybe third one will be the charm.