Automotive Air Conditioning Information Forum (Archives)

miked on Sat July 14, 2012 6:47 PM

Year: 1998
Make: chevy
Model: 1500
Engine Size: 350
Refrigerant Type: 134a
Ambient Temp: 110
Pressure Low: 90
Pressure High: 220
Country of Origin: United States

Just replaced compressor ,accumulator, high low pressure hoses , evaporator to condesoner line , condesoner , orifice tube . put 3 oz of pag oil in compressor and 4 oz in accumulator ,pulled vacuum -29 ,no leaks . used a 12 oz. can of freon containing one oz. of oil . started charging compressor cycled on and off until maybe more then half of the can was gone then stayed on , proceeded to add second can and the system didnt seem to have much suction. pretty soon the low pressure side was up over 100psi . air coming out the vents was 80 degrees , very disapointing . maybe got 24 oz in the system , checked high and low pressure with pro gauges 90 on the low side over 200 high side .the air is only cold at highway speeds but even then only 60 degrees coming out the vents . i am completely perplexed . i have two electric fans instead of an engine fan. one fan is temperature driven and the other is switched on by the ac compressor. is there a blockage somewhere , did i miss a step somewhere, am i cursed i dont know. this truck hasnt ever had really awesome air but i thought by replacing everything i could start fresh. we have a 07 avalanche and that thing is like antarctica on wheels . somebody help me please or im doomed to go to a professional and probably have to use my kids college fund to get it fixed ......

bohica2xo on Sat July 14, 2012 7:36 PM

The first question is, why was all of this replaced? What had failed?

Is this a new or remanufactured compressor?

At first glance it looks like your gauge is not depressing the valve in the low side connector properly.

B.

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"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

miked on Sat July 14, 2012 7:48 PM

the compressor failed was leaking oil . so i got a new compressor and dryer and orifice tube as part of package deal. changed all that then when i was removing the the lines to the condesoner the threads got trashed so got a new condesoner and all new pressure lines. so needless to say i spent alot to get to where i am currently at. the gauges quick connects have an open and close knob. thanks for taking the time to read my problem and respond .

mk378 on Sat July 14, 2012 8:20 PM

You need a full charge to properly evaluate performance. Works only on the highway with high pressure sitting still means that the condenser / fans are not adequate.

miked on Sat July 14, 2012 8:26 PM

so would a fan attached to the condesoner help ? i dont understand how the factory mechanical fan and shroud could be more efficient then these two fans , the engine temp. seems well regulated by the electric fans . i dont get why the gap between the radiator and the condesoner is so big , how could any fan move air thru the condesoner while sitting still. i dont want to remove the electric fans but i will if that is the problem ?

mk378 on Sat July 14, 2012 8:55 PM

It takes a lot more air for proper A/C performance than just what it takes to keep the engine at normal temperature. At the very least, wire it so both fans come on when the compressor is on. Even that is much less than the engine-driven fan does.

Also if the compressor was cycling on the low pressure switch, the low side pressure should have been down in the 20 to 40 range. While you have the valve open to charge, you're reading mostly the pressure from the refrigerant can. The valves on the manifold must be closed for the gauges to read the actual system pressure.

Edited: Sat July 14, 2012 at 8:58 PM by mk378

bohica2xo on Sat July 14, 2012 8:58 PM

You do need a full charge to evaluate. The gap between condensor & radiator is always an issue - we usually close that up with some foam weatherstrip.

Hose the condensor down, raise the engine rpm to 1500 & get the rest of the charge in.

To evaluate the ram air vs fan air question, duct tape the gauge set to the windshield & go for a drive.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

miked on Sat July 14, 2012 10:00 PM

so should i replace the electric fans with the engine fan then ? is it possible that the power flush product i used maybe loosened some gunk and could have clogged the orifice tube ? i remember the old tube had a little gunk in it . yeah 90 low side over 200 high side was at the manifold i was just trying to get readings no charging was involved .

bohica2xo on Sat July 14, 2012 10:25 PM

Any flushing agent needs to be removed before filling the system.

Are you sure there is only one orifice tube in the vehicle?

Like I said, get a full charge in it before you decide on the fans. The mechanical fan is very powerful, and may be necessary at your high ambient temps.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

miked on Sat July 14, 2012 10:39 PM

i used the power flush and then compressed air to blow it out . so at 1500 rpm will the pressure drop ? so run water over the condesoner , rev the engine up to 1500 rpm and this will create suction ??

iceman2555 on Sun July 15, 2012 9:49 PM

Several post have stated that the system must be properly charged. Forget all attempts to determine a problem until the system is properly charged. A possible reason for the excessive low side pressures is the lack of system performance. If the evap can not begin to cool, the low side pressures will be high. Get the evap cold...needs more refrigerant to accomplish this and then check the system. This vehicle requires 36 oz of refrigerant. The posted charge is too low for the system to begin to cool the system with your posted ambient temperatures. Have the system serviced by someone with the correct equipment to properly charge the system. Then complete the evaluation of the system.
Also, check the routing of your hoses, on this vehicle the discharge hose (compressor to condenser) and the liquid line (condenser to evap) can be reversed. Also, insure that the liquid side of the condenser ( look for notch for orifice tube) is on the bottom. This issue can complicate pressure issues also.

Also what type electric fans are installed on this vehicle? Most aftermarket fans (AZ, ORiellys, Advance) lack sufficient air flow for many vehicles. This vehicle needs app. 2500-2800 cfm to properly cool in high temps.

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