Year: 1999
Make: Chevy
Model: Tahoe
Engine Size: 5.7
Refrigerant Type: 134a
Ambient Temp: 90
Country of Origin: United States
Compressor is short cycling. Replaced low and high side switches. Freon level is good according to an "idiot light" type of recharging tool. I can feel the low side muffler and lines start cooling for the few seconds that the clutch engages and if I jump the switch and let it run.
Any ideas? Thanks in advance!
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DAMelvin
65% of mobile a/c failures are due to loss of refrigerant-- yours fits this statistic--get a good gauge- rapid cycling is telling you this-- just listen
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The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......
Thanks for the info. I did buy gauges. Not real familiar with them yet. Wasn't sure if my readings were correct because the compressor wouldn't run at all at that time(relay).
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DAMelvin
Pressures first, this will tell you if you have a bad cycling switch cutting the compressor off to soon, or if you are low on charge (Most likely) Or if the high side is shutting it down, but I doubt it, I agree with GM tech, low charge...Hope this helps..
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Chick
Email: Chick
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Freedoms just another word for nothing left to lose
Low side 24, high side 25. readings do not change whether running or not.
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DAMelvin
System is empty...
Common leak areas are the front shaft seal, most common is the seams of the compressor as the below pic shows. Hope this helps...
PS> If you have the dye on the compressor, I recommend the HT6 clones available from Ackits.com..
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Chick
Email: Chick
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Freedoms just another word for nothing left to lose
Edited: Fri June 05, 2009 at 6:39 PM by Chick
Okay... I jumped the low side switch and added freon. Noticed the line freezing right at the connector where the orifice tube is. Replaced the orifice tube and the o-ring. Vacuumed to about 21-hg. Using a compressor type vacuum pump. Thats as low as it would go after 35-40 minutes. Jumped the switch again and added 3 and about 1/2 cans of freon. I did reconnect the switch after the second can and the clutch stayed engaged much longer. Idiot light type recharge tool says "proper charge". Gauges now read -5 to - 10 low side and 45 high side. Getting as low as 60 at the vents inside.
Obviously still not cooling correctly. Book I have says 64 oz of refrigerent. I only added around 40. Stopped because "idiot light" tool I am using says so. Maybe reading wrong because vacuum wasn't as good as it should be? I am in Florida so shouldn't I be at 29.92?
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DAMelvin
You need the full amount added back, if you don't have the proper gages, at least add the full amount..If you have no restrictions it will cool once full. How did the O tube look??
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Chick
Email: Chick
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Freedoms just another word for nothing left to lose
I have the gauges, just not sure how to use them when charging. The orifice tube was black but didn't appear to be clogged. Do you think the vacuum I pulled will be enough?
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DAMelvin
You need the full amount in the system, do not run it while low. You can burn out your compressor. Your vacuum is not enough to boil off moisture, but it is better than nothing.. Your O tube was black? Thats a sign of burned oil, or ground up aluminum, etc.. It would be best if you found and fixed your leak, flush the system, add back the proper amount and type of oil and be done with it. Or you can take a chance and run it the way it is, but again, make sure you have the full system amount in there before you use it..
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Chick
Email: Chick
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Freedoms just another word for nothing left to lose
So just add the additional 24 ounces? Do you suggest the freon with the dye to find the leak? And if I add freon using the manifold will the dye harm it?
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DAMelvin
Dye will not hurt the manifold, and yes, add the proper charge to the system, you may not have much of a leak anyway, it's ten years old, might have been a normal loss..?? Charge it up and use it.. Check for leaks after a while..
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Chick
Email: Chick
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Freedoms just another word for nothing left to lose
I checked the tag under the hood (what a concept!) and found that I have added the proper amount of refrigerant. I am getting 60ð at the front vents and 50ð at the rear vents (I have rear a/c). The static pressures are: 23low and 20 high. The performance pressures are 0 low and 60 high at 1500 rpm. The low side lines are very cool but not freezing up, but the high side are very hot just before the compressor.
Thanks again for everyone's help.
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DAMelvin
"IF" those static pressures are correct, your system is empty.. If it's 90 degrees outside the static pressures should be around 90 on a cold engine, and higher on a hot engine.. I suggest you recover the refrigerant and add back the amount on the underhood sticker, and don't stop charging until it's all in there.. Or you're not hooked up to your service ports correctly..
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Chick
Email: Chick
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Freedoms just another word for nothing left to lose
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