No heat in 97 grand cherokee laredo

[redearthman]

Hi all,

I have read a ton of posts on this issue and checked into everything. I cannot figure out my problem. Replaced radiator, water pump, 2 thermostats, heater hoses get hot, had it flushed professionally and they stuck a high pressure hose to the heater core and it flows good, checked blend door actuator and it works, the plastic piece is not broken and the door makes a flapping noise when i switch it by hand with the actuator off, blower works good all speeds, what am I missing? Some guy told me it could be vacuum to heater core that closes heater core off in case of leaking, there are not leaks anywhere, could that be it? Should I try the heater treater fix? What are my options? I'm sooooo cold.

Update* I looked everywhere for a vacuum line to the heater core and could not find one. After changing my thermostat for the second time with a higher quality one its even colder now, it was luke warm now its just cold, but when I switch to the cold setting I can tell that it shifts and is even colder. When I tried the blend door actuator by hand and its makes the flapping noise and then if I turn on the blower i can no longer move the actuator/blend doors by hand because of the air traveling through it, does that mean the doors are good and no heater treater fix needed? Please help. Its running at 200 degrees even

 

[jimbob2001]

Sounds. Like you have DONE most everything! Ouch! I have HEARD that the BLEND DOORS can be a problem on the Cherokees! Also the Actuator housing can be a problem! The Dealer probably would want $1500 for this Repair! I have heard of GUYS buying. The Blend. Doors and going in THRU the Glove Box - cutting a hole in the Plastic to reach the ASSEMBLY -- then using Silicon to put it all back together! Beats taking the. DASH OFF!! GOOD LUCK! JB

 

[SteelHeadz]

If both heater core lines are heating up close to even temperatures then the issue would be in the HVAC doors. Either the mode/blend door or actuatator is at fault. Is this a single or dual temp unit and is it auto or manually controlled system?.

 

[redearthman]

Its a single heat control. So you think the heater treater fix will be my next bet? Not sure about auto or manual control, what's the difference? There are 3 controls, fan, location, and temperature (circular dials) the temperature control adjusts the actuator motor just above the hump under the dash. I took it off and the plastic thing is ok and i can move the door and it makes a normal sounding noise but God knows whats going on in there, its at 200 degrees with a 190 t-stat and it should be belting out the heat, the heater hoses seem to be the same temperature to the core.

 

[SteelHeadz]

From what you have described, you have a manual hvac control. Having verified the heater core temperature to be relatively the same on both inlet and outlet indicates an hvac door or actuator issue. You have verified that the door behind the glovebox, (left side of the opening) is intact and moving. By doing this, did you verify that the actuator is actually moving when you switch the hvac controls in different modes?. Move the hvac knob in all the modes with a 3-4 second delay in between modes to verify IF the actuator you removed is moving. You can do this in all of the actuators that is accesible to you without removing the dash to test whats working and whats not. Also, when the engine is at normal operating temperature, while the actuators are disengaged from their respective positions, manually move the doors with your fingers and see which door is responsible for the temp./mode, feel the air in the vents on which vent is the air coming out of and temperature. This will pinpoint which door you need to concentrate on. The best test i do is with the use of the Chrysler scan tool(DRB3). This scantool can test the door span and actuators without having to physically remove and verify the actuators and doors. Your local dealer should be able to help you with that if you choose to go that route.

 

[redearthman]

Thanks for the information I will try that and see what I find and post back soon.

 

[redearthman]

Anybody know where the heater control valve is located on this vehicle? 97 jeep grand cherokee laredo 4.0 v6 4x4, is there a vacuum line somewhere to the heater core to shut the flow of water off to it? I need to check that before I cut a hole in the dash, but I cannot locate it. Any body got a pic of the location please?

 

[SteelHeadz]

Your GC does not have a heater control valve. The hvac system consis of both vacuum actuator and electronic actuators. Here's some diagram for refference.

 

[redearthman]

Thanks for the information and diagrams, I've determined that it is the heater core. I had it flushed professionally and it must be partially plugged and had an air pocket or something in it. I hooked a garden hose up to it and water flows cleanly, after I did that I have more heat, something that actually resembles heat so its partially working now, yay! it was 27 degrees out this morning, defrosted well and warmed the cabin to a comfortable level. I called and was quoted 550 to repair, so I will wait on that and see how it goes, thanks for all the help.