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Amedee
Amedee, Jeep Technician
Category: Jeep
Satisfied Customers: 21899
Experience:  ASE Master Technician advanced level specialist. Wisconsin certified emissions state inspector
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grand cherokee: my 95 v6..replaced thermostat no help...core

Customer Question

very little heat on my 95 v6 grand cherokee. replaced thermostat no help. Is this the dreaded replace of heating core? there is no ac either so if so I could replace the evap core while im in there. sound right, any easy way to take the dash out which im sure I need to???
Submitted: 4 years ago.
Category: Jeep
Expert:  Amedee replied 4 years ago.

Greetings!

The heaters heat comes from the engine tempature. The first thing u will need to do is make sure the engine temp is up to par. 200 degrees is normal operating temp. This is the job of the thermostat. If it is stuck open or stuck closed the engine will not get up to and maintain 200 degrees. If that checks out ok, next step would be to make sure the coolant is full and there are no air bubbles at all in the system. Air pockets in the system will cause a no or low heat situation. IF there are air bubbles or air pockets you will need to bleed the system. Warm up the car with the radiator cap off while topping off the coolant. The air bubbles should rise out the top. If your engine has bleeder screws, unscrew them to release the air that is trapped inside. If there is no bleeders than you can cut a hose near the top of the system and put a flushing tee in line and you can just unscrew the cap to let the air out, than tighten the cap back up when you are done. Next would be the heater hoses. Make sure both of them going into the heater core are the same temp. If they are not, the heater core may be plugged and need to be flushed out. Hope this helps!

 

Amedee, Jeep Technician
Category: Jeep
Satisfied Customers: 21899
Experience: ASE Master Technician advanced level specialist. Wisconsin certified emissions state inspector
Amedee and other Jeep Specialists are ready to help you
Customer: replied 4 years ago.
Yes the engine temp is running in the 155 range. This is the way it's been sence the theromstat was replaced. Could it be the wrong value thermostat?
Expert:  Amedee replied 4 years ago.
Well, yes... this is a problem. You could have a bad thermostat or something else causing the engine to run this cold. We need to get the engine up to operating engine tempature. 195 to 200 degrees F
Customer: replied 4 years ago.
So I replaced the tstat, again. bled the radiator. still only getting up to 160-165(no change) any other ideas?
Expert:  Amedee replied 4 years ago.

Where on the engine are you getting only 160-165? Where you are checking the tempature? Or are you relying on the temp gauge on the dash?

Customer: replied 4 years ago.
the gauge on the dash, but I assume its close as the heat is weak. I know that could be wrong, but if it is then what do I do about the heater???
Expert:  Amedee replied 4 years ago.

Well, you could be right... the gauge could be close and the engine could just not be getting up to operating temp. Basically what needs to be done it a temp gun needs to be used. We need to take tempature readings in various places of the engine block and heads to be sure the gauge is in fact accurate.

 

If the gauge is not accurate, we could have a bad temp sensor, wiring or instrument cluster issue.

 

If the gauge is dead on, then the engine is not getting up to operating temp for some reason and we will have to do some further investigating.

Expert:  Amedee replied 4 years ago.
Test the resistance of the sending unit. At 100 degree on gauge the sending unit should be about 1365 ohms. At 220 degrees on gauge the sending unit should be about 93 ohms. At 260 degrees on the gauge the sending unit should be about 55 ohms. Replace the sending unit as needed.
Customer: replied 4 years ago.
but that shouldn't effect the heat temp in the cab, right? I don't care as much about that as I do my heater working when it's cold here in montana
Expert:  Amedee replied 4 years ago.

Correct!

 

Check the heater hoses to be sure they are the same tempature.

Expert:  Amedee replied 4 years ago.

Here are some tests to run to diagnose the problem.

 

Test the system from the floor vent at idle with the blower on high speed. The specifications for heater output are as follows: 60 degrees ambient temperature = 144 degrees, 70 degrees ambient temperature = 147 degrees, 80 degrees ambient = 150 degrees, 90 degrees ambient = 153 degrees.

If the output is low, then remove the blend air actuator and check the door for sticking. Try manually closing it and rechecking the temperature. If the door is sticking, try to free it up or service as needed. \

 


Test the system from the floor vent at idle with the blower on high speed. The specifications for the heater output are as follows: 60 degrees ambient temperature = 144 degrees, 70 degrees ambient temperature = 147 degrees, 80 degrees ambient = 150 degrees, 90 degrees ambient = 153 degrees.

If the output is low, then remove the blend air actuator and check the door for sticking. Try manually closing it and rechecking the temperature. If the door is sticking, try to free it up or service as needed.

 

Potential Causes:

Actuator
Blend Air Door
Control Head
Wiring

Customer: replied 4 years ago.
where is the air blend actuator? thanks for all the insite BTW
Expert:  Amedee replied 4 years ago.

Under neath the dash on the HVAC assembly. If my memory serves me correct, its on the passenger side. Here is a picture.

 

graphic



Edited by AMEDEE on 12/19/2009 at 6:47 PM EST
Customer: replied 4 years ago.
by low output do you mean temp or air output, it blows fine. do i need to remove a cover here to find the blend door
Expert:  Amedee replied 4 years ago.

Tempature.

 

I believe there might be a plastic cover that you will have to remove to gain access to the blend air door unless its been removed already.

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