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1999 Jeep Cherokee Evaporator Problem

dwvsplat on Wed September 05, 2007 8:22 PM User is offline

Year: 1999
Make: Jeep
Model: Grand Cherokee
Engine Size: 4.0
Refrigerant Type: R134a
Ambient Temp: 85
Pressure Low: 35
Pressure High: 240
Country of Origin: United States

I am having a problem with an evaporator install. I put a new evaporator (aftermarket) in a customers 99 jeep grand cherokee, pulled vacuum for about 1 hour (-30 psi.). I filled it with 2 12 oz. cans of r134a (24 oz.) and 1 oz. of dye. I was running about 34psi on the low side and about 220 psi on the high side. I am getting no cool air at all. I was having a hard time trying to get the compressor to pull any r134a into the system. My thought was the compressor was going bad, but I do not know. The customer said he was putting 2 cans in before I did the evaporator and he was running with very cold air conditioning. What did I do wrong?

Chick on Wed September 05, 2007 8:32 PM User is offlineView users profile

Feel the inlet and outlet of the evap..Same temp, with the outlet (suction side) a little colder, then you have a blend door problem. If not colder or as cold, then ask the customer what he added.. Any sealers with his "two" can additions, and how often.. Pressures show the compressor is working..So i would look for temp difference in the evap first, and let us know what you find..Be sure fan(s) are operating properly also..
PS: Did you change the O tube and accumulator?? The O tube may be part of the liquid line..Not sure on the 99 model year..

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

iceman2555 on Wed September 05, 2007 8:37 PM User is offlineView users profile

First test...is the evap outlet cold ? If so, then the system is cooling and it is probably a problem in the plenum or temp blend door.
Pressures look good, however, have seen instances where the flow of refrigerant due to high heat load in the condenser produced some similar pressures but no cooling.
From what was stated concerning the compressor...it is possible that the compressor is bad....operation without sufficient refrigerant can result in excessive compressor wear and possible loss of pumping efficiency. Although the statement that the customer had very cold air before...may discount the bad compressor theory...however, keep in mind...we all know when a customer is lying....right......whenever his lips are moving.
Any way...determine if the evap outlet is cold...sweaty, and attack the problem from that point. If the evap outlet is warm...no sweat.....leans toward the compressor as the culprit.
Good luck !!!!

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The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

dwvsplat on Wed September 05, 2007 8:57 PM User is offline

The line is extremely cold. And I am getting condensation dripping from the drain line. I have turned the heat and cool selector (evaporator/heater core) and I get great heat, and then almost no ac. The cooling fan is stock engine mount (no electric fan). The customer is a good friend, so I do not think he is lying to me. The evaporator fit really sloppy in the slot of the hvac system. Am I going to have to pull the dash out again to fix this thing?

Chick on Wed September 05, 2007 9:00 PM User is offlineView users profile

If the suction line going back to the compressor is cold, the system is working and the fault is in the blend doors somewhere.. they are a real pain to remove and replace...

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

chris142 on Wed September 05, 2007 10:04 PM User is offline

Ya blend doors are a common problem on this model. Jeepsunlimited.com has a write up about it.

Did you really put a whole ounce of Dye in it?

http://www.jeepsunlimited.com/forums/showthread.php?t=840602&highlight=blend+door

http://www.jeepsunlimited.com/forums/showthread.php?t=771954&highlight=blend+door

dwvsplat on Thu September 06, 2007 8:28 AM User is offline

If it is the blend door, wouldn't it effect the heating also? I can turn it to heat and the system works fine. The selector from vent to floor to defrost works fine also. Is the electric motor in the back of the hvac (dash side behind the glove box) the control motor for the blend door?

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