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cold in front /warm in back

arnea on Sat July 19, 2008 11:03 AM User is offline

Year: 1997
Make: chev
Model: suburban
Engine Size: 5.7
Refrigerant Type: R134a
Ambient Temp: 90
Pressure Low: 35
Pressure High: 220
Country of Origin: United States

I replaced the compressor/OT/dryer/ flushed system evac and added 4 lbs. Front blows 38-40 degree air. but seems to barely keep up although when your moving faster a little better. rear air blows warm air. What to do?????

Chick on Sat July 19, 2008 11:40 AM User is offlineView users profile

Did you remove the rear expansion valve when you flushed? or did you flush thru it??

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

iceman2555 on Sat July 19, 2008 5:17 PM User is offlineView users profile

From the pressures posted...and the symptoms...seems as if the system is a bit undercharged. Was the system charged using the correct recharge type equipment to facilitate a true weight or was it charged with cans and anticipation of a fully charged system with a determined pressure reading? It is expected at the given ambient temp that both pressures would be a bit higher....possibly 235-250 high and 42-46 low. An attempt to balance charge rate using pressures is best left to the pros....and that is still an inexact procedure.
Try adding a bit more refrigerant...say 2-4 oz...allow the system to stabilize and test....it often takes as much as 10-15 minutes for these larger system to fully stabilize.
One good test....max air....high blower....engine at idle....doors open...rear air blower in the off....test the inlet and outlet temps of the evap...should be equal...or within 3-5 degrees of each other...once this condition occurs....then activate the rear unit....allow to stabilize...and retest temps...post info.
Another aspect...check the rear lines for possible damage....crimps...etc...anything that would restrict refrigerant flow to the rear unit. A good test is to measure the temp between the inlet and outlet of each line and look for a major temp drop between these points.
However, from the description of the condition....and the pressures indicated....my first suspect would be an undercharge. Moving faster with a slightly undercharged system would increase the cycle points of the compressor and this would naturally reduce cooling efficiency



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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

arnea on Sat July 19, 2008 7:01 PM User is offline

I did not open the rear expansion valve assy just flushed through it. I did run for over an hour on the road with no improvement? to the rear. I did change to an after market condenser last year when it got hit. I am wondering if that could be part of the problem???? I did use a 30 lb tank with a proper scale and vacuum pump... Arne

iceman2555 on Sat July 19, 2008 8:42 PM User is offlineView users profile

Was this problem evident prior to the 'flush' job....? What is the construction material of the condenser...alum...or brass and copper?
Never been a advocate of flushing thru a TXV.....also the chance of introducing contaminants into the valve....could result in a stuck valve..either open or closed. This system is so large that it is possible for the system to absorb this problem and not indicate a problem with pressures.
If you are assured that the charge rate is up to par....did you add sufficient refrigerant to pre fill your hoses......then it is quite possible the culprit is the TXV......first would want to be absolutely sure the system is fully charged.
Access the rear TXV and check for possible frost on the valve..or check in/outlet temps of the valve itself...this will tell much about the condition of the valve.
Goof 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

Chick on Sat July 19, 2008 8:56 PM User is offlineView users profile

One point that needs to be said, if the valve wasn't removed, there is little chance that all the flush material was removed..That will degrade the new oil, and cause a compressor failure down the road..You need to recover the refrigerant, remove the rear expansion valve and then re-flush the system again properly. Change the rear expansion valve since you'll have it off..Plenty of shop air to blow the flush out and dry the system before adding back the proper amount of oil...Hope this helps..

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

iceman2555 on Sat July 19, 2008 9:06 PM User is offlineView users profile

Agreed...esp consider the type of flush solvent used!!! May even consider a change in flush chemicals...depending upon what type was used initially.


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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

HECAT on Sun July 20, 2008 9:22 AM User is offline

In addition to the fact that debris can be pushed to or into the TXV and cause problems; I will add some thoughts based on many tests we have done on the "flushing thru the TXV" issue. Flushing thru the TXV can be done (as the poster has done) but recovery of any type of flushing agent other than a refrigerant with a minus zero boiling point cannot be done. Solvents require the forced air process to remove, unless it is an oil based flush in which case forced air becomes useless. With the forced air restricted by the TXV, evaporation does not occur as desired. Trying to back blow does not eliminate this restriction and some TXV's will even throttle closed at low pressure, completely closing the path. This is only regarding recovery as flushing thru a TXV also kills any solvent velocity which is also critical to successful cleaning.

1. Oil based flush cannot be removed with forced air or vacuum.
2. Solvent based flushes can be removed with forced air but not vacuum.
3. Refrigerant cleaners can be removed with vacuum.

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FLUSHING TECHNICAL PAPER vs2.pdf 

arnea on Mon July 21, 2008 9:38 AM User is offline

Thanks for the information: I used the flush from this site. I will open the system again and also open the rear system flush again, replace the expansion valve and try again. Do you recommend empting thencompressor of it oil ???? Also should I go back to a AC Delco condense and add a fan assy??? Thanks Arne

HECAT on Thu July 24, 2008 5:25 PM User is offline

Sorry for the delayed response, I have been away for a few days.

If you have not already completed the repair...

If you got the flush from this site through the rear TXV, you probably got some into the rear evap that did not come out with the air blow. Removing the rear TXV and flushing the rear evap and blowing dry will be the plan. The same is true for the front evap, remove any restriction such as the o-tube so you can flush and dry the component. Because of this potential problem, the oil may be diluted with solvent so, yes the compressor should be oil flushed. I cannot answer about the condenser as I am not familiar with the reason you replaced the compressor and what method you have available to use the flush. If it was an explosive failure and you do not have power flushing equipment, replacement of the condenser may be in order. If it was not, then flush it again. Make sure everything is dry, dry, dry and use a blow gun to "pop" test to be sure. The fan is never a bad move, as they do wear out; use OEM.

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HECAT: www.hecatinc.com You support the Forum when you consider www.ackits.com for your a/c parts.

FLUSHING TECHNICAL PAPER vs2.pdf 

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