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Roy, import/domestic specialest
Category: Chevy
Satisfied Customers: 5600
Experience:  ASE master tech for 40 years
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I have a 2003 Tahoe with an AC issue the High and low side

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I have a 2003 Tahoe with an AC issue the High and low side pressures are near normal but the cooling is 60F at the dash vent with a 85F ambient temp outside. The low side pressure is 65psi and the high side is 225 but the pump runs and doesn't cycle. WHat am I missing ? Thanks

HI,

Can you get me the high and low side readings with ac off.

Customer: replied 11 days ago.
The high side is around 135psi with the AC off the gauge on the Low side goes into the "Retard" area.

HI,

The readings point the orifice tube being restricted which will cause a higher than normal low reading and will prevent the system from equalizing when ac is off.

Customer: replied 11 days ago.
The orifice tube looks perfectly clean no debris or damage.

The only other cause I see would be a slightly weak compressor

Customer: replied 11 days ago.
How can I verify that before I throw one at it? The compressor doesn't shut off it runs constantly but it wont get over 250 psi even bringing the engine to 2000 rpm. I just want to insure that Im making the right call before I condemn the compressor.

HI,

The pressures are what one normally uses in determining whether the compressor is good or not. Higher than normal low pressure reading is usually either restriction in the orifice tube or weak compressor on the suction side. Couple that with the high side not getting over 250psi, those do indicate a weak compressor, along with inability of the system to equalize.

Customer: replied 11 days ago.
basically my best call is to replace the compressor, dryer & orifice tube re-vacuum the system.

HI,

Yes, based on the readings and symptoms.

Customer: replied 11 days ago.
OK Thank you for the information

you are welcome

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Customer: replied 11 days ago.
Can I wait to rate it after I replace the parts to see if the recommendation works? What you have told me so far I have no issues with and agree with you. However the repair isn't make therefore I cant comment accurately on the diagnosis Is that fair?

HI,

Yes, that is fine

Customer: replied 11 days ago.
Perfect Thanks Eric

you are welcome

I noticed we have not yet resolved your concern you asked about. I would sure appreciate it if you would reply so I can offer my skills and knowledge and repair guide access to help as best I can.

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Customer: replied 1 day ago.
The changes recommended did not fix the issue the A/C will still only cool down to about 58F the low side pressure is still high with the pressures at 55-65psi and the pump runs non stop the high side sits about 225psi the ambient temperature was 89F on the day I was trying to get the thing to cool. I replaced the dryer and the compressor as suggested vacuumed for 60 min and recharged with 3.0 lbs of Freon, with a new orifice tube as well. I have never had issues like this in 20 years of doing A/C work.

this has front and rear ac in this vehicle ?

Customer: replied 1 day ago.

can i ask did you add oil to the system and how much did you add total when those parts where changed ?

Customer: replied 1 day ago.
3.0 oz per the recommendation on the new pump instructions 1.0 oz for the new dryer installed and 1.0oz to replace the possible loss from evacuating the system so a total of 5 oz

ok

can you try 2 things next

with the ac running and the truck on if you spray water on the condensor with the hose will the low side drop down and will it cool when your running water on the condensor ?

if not with it running drop out some freon until the low side reads 28 to 30 with the compressor running and will it then cool ?

Customer: replied 1 day ago.
Spraying water on the condenser doesn't change anything. If I drop out Freon to that point only the rear AC works it will cool to about 42F at that point but the front will be at aprox 60-62f

so you dropped it down to 30 on the low side and it is still not cool ?

Customer: replied 1 day ago.
Not on the front only the rear cools with it at that point

do you still need help??

Customer: replied 1 day ago.
You can read through the issue that I am having with this AC on a Tahoe ?????

read through it already

couple of questions

1. what are the pressures now with the ac off??

2. did you add all the oil to the freon system or compressor 5 oz and 2 in the freon system.

Roy

Customer: replied 1 day ago.
Im not at the barn now I am at work the system equalizes at about 90 PSI from what I can recall from last week. 3 OZ in the compressor 2oz in the system.

ok, good the static pressure should be at ambient temp and equal. ant variance indicates an issue with the orfice tube.

high sides should be 2 times outside temp plus 15%

low side should be 25-30.

inside air temp or duct temp should be 30% lees than ambient temp as well.

Roy

Customer: replied 1 day ago.
180+27=207 High Side I am at about 220 Low side @ 55-60 Psi Inside duct temp 90f - 27 (30%) = 63 I have a duct temp at idle about 60f. Driving down the road its 42f are you telling me that its normal and I don't have an issue? The low side is still to high and the compressor never kicks out and I have used 2 brand new orifice tubes same result.????

the low side is definitely high and your high side is as well.

it almost sounds like you are overcharged. did you use a ac machine to add the freon or cans???

Roy

Customer: replied 1 day ago.
Robinair AC machine the only way that I can get the low side below 30 psi is to fill it with half the recommended Freon and then the front AC doesn't cool at all its weird in 20 years of doing AC work I have never had an issue like this one.

so, you only have 1.5 lbs in the system???

Customer: replied 23 hours ago.
To get the low side pressure below 30 Psi that's correct.

did you check the rear orfice tube

the high low side is either a orfice tube or restriction in the evap

Customer: replied 23 hours ago.
I did Not Most of these that I have done have a rear expansion valve. Even if the rear was completely blocked though the lines have a tee in them and shouldn't cause this issue ( correct me if I am wrong ) Furthermore if the rear had an orifice tube blockage the rear AC wouldn't work correctly and it does. ????

what color orfice tube did you install?

was it the same color you removed???

Customer: replied 23 hours ago.
How can I prove that before making a call for the entire dash to be removed to replace an evaporator??
White and Yes

if all you say is true we have eliminated it down to this. before doing it. I would flush it first and see if there is any debris in the core

Roy

Customer: replied 23 hours ago.
Is there a good flushing agent that you would recommend ?

it has been years since I did one. I remember getting it at NAPA but dont remember the name

Customer: replied 23 hours ago.
Ok sounds good I will try it out and see if it helps. Thank You

your welcome

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Roy

Roy, import/domestic specialest
Category: Chevy
Satisfied Customers: 5600
Experience: ASE master tech for 40 years
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thank you