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01 Tahoe AC WOE and puzzlement
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comnavguy
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Jul 9, 2011, 12:30 PM
Post #1 of 9
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01 Tahoe AC WOE and puzzlement
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The owner of this vehicle with dual AC had the hose from the compressor to the top of the condenser replaced. The system was vacuumed and recharged but it did not cool at all. I do not know why the other mechanic quit.
When I put my gauges on, the high side was 125 PSI. The low side was 70 to 75 with slight fluctuation. Increasing RPM would bring down the low to 60/65 and my sight glass showed a little freon being added but with no change in the high side pressure.
NOTE: The high side is separated by one joint and the orifice tube from the low service port.
I replaced the DIRTY, half-clogged orifice tube, re-vacuumed the system, which held vacuum for over 30 minutes. I then attempted to re-charge. Low side would never get below 60 PSI and high would never go above 125 - 130 with no cooling whatsoever.
I have never seen the high service port and the low service port in the same line separated by only an orifice tube.
I need some 'splaining and help. The book calls for 4 lbs of freon. I can't see how it would be possible to add any more freon than the approximately 1 lb I've charged so far.
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Hammer Time
Ultimate Carjunky
/ Moderator
Jul 9, 2011, 1:07 PM
Post #2 of 9
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Re: 01 Tahoe AC WOE and puzzlement
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Ther orifice tube is what changes it from high to low so that works fine. It sounds like you have a bad compressor but have someone else start the truck and turn the A/C on while you feel the temp of the liquid line on the high side. You should feel a warmth, not hot almost immediately and it should remain that way. If it never warms up or changes to room temp, then you could have a blockage but that is rare on a CCOT system.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Tom Greenleaf
Ultimate Carjunky
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Jul 9, 2011, 2:11 PM
Post #3 of 9
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Re: 01 Tahoe AC WOE and puzzlement
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Did I see that you only have 1 of 4 lbs in there? Are you forcing the compressor with that low of a charge? That and I can't see how you couldn't get more into non running system just into the vacuum. Bet compressor is fried from lack of oil as that low a charge isn't going to carry enough oil if so,
T
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comnavguy
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Jul 11, 2011, 7:01 AM
Post #4 of 9
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Re: 01 Tahoe AC WOE and puzzlement
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No, no, no. I Never force a compressor to run. I vacuumed the system and then charged one 12 oz can with the truck off. Then, I started a 2nd can and about half way through no freon was moving through the sight glass with the low side at about 70 PSI. I had the owner start the truck. The compressor clutch engaged immediately.
The high side went to about 100 and the low was around 60 - 65. It took a little more freon from the second can and then the flow stopped. The high side was about 125 with the low side hovering close to 70.
I can not understand how much more freon could be charged with such a small differential pressure between the charging port and the pressure in the can of freon.
I even tried a second set of gauges just in case my first set low gauge was off.
Any other suggestions or help will be greatly appreciated.
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Hammer Time
Ultimate Carjunky
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Jul 11, 2011, 8:05 AM
Post #5 of 9
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Re: 01 Tahoe AC WOE and puzzlement
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Did you do the feel test I suggested?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jul 11, 2011, 8:11 AM
Post #6 of 9
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Re: 01 Tahoe AC WOE and puzzlement
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Quote">>No, no, no. I Never force a compressor to run. I vacuumed the system and then charged one 12 oz can with the truck off.<<"
Good! I bought out a place dumping the stuff so cheap by the 12oz cans (same stuff) I couldn't resist. Like $1 buck a can! OK - they get cold quickly vs a 30 pounder so need to be shaken and warmed by your hands or warm water. The shaking of the can you get spits of liquid in which is faster and warm water handy in a pan helps. Easy on liquid charge after first can and when port is close to compressor you can gag one with a rush of liquid - that isn't good causing hydraulic lock is too effective getting it in so upright can (vapor) is safer but can still be quick.
This and other gasses that condense are very temp/pressure related. Ex: at about 70 PSI and 70F pressures are equal so nothing is going anywhere.
If you know the temperature you know the pressure. There's a chart here as to exactly what that is once locked at the top of this section but I unlocked it as it's annoying to have too many locked posts at least to me. Did lock "Charging Procedures" which is full of good info and probably could just add that chart to the end so would be one spot.
Had to get an infrared thermo to measure pressure as more and more cars/vehicles don't come with a high side port at all! Azzholes try to save a buck anywhere but it's useful info to know high side of course,
T
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Discretesignals
Ultimate Carjunky
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Jul 11, 2011, 9:49 PM
Post #7 of 9
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Re: 01 Tahoe AC WOE and puzzlement
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Just curious. What was the orifice tube plugged up with? desiccant or pieces of the compressor? If the orifice tube screen was plugged up with garbage I am sure the expansion valve in the rear evaporator isn't much better. If the expansion valve is plugged up, your going to have a hard time getting 4 lbs of refrigerant in there.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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comnavguy
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Jul 11, 2011, 10:16 PM
Post #8 of 9
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Re: 01 Tahoe AC WOE and puzzlement
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The truck was being driven by the owner all day. I didn't have a chance to do the hand test. That last post was elaboration of the first post, explaining that I had not forced the compressor on.
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comnavguy
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Jul 11, 2011, 11:43 PM
Post #9 of 9
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Re: 01 Tahoe AC WOE and puzzlement
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The first two screens were about 30 Percent clogged with graphite-like greasy residue that had tensy tiny flakes of metal. I've seen'em far worse with all screens clogged more than 30 percent with the same greasy substance and still working - not great but working.
Before I opened the line to replace the orifice tube, I had 125 high; 65 - 70 low. I replaced the O tube and with only about 1 pound of freon, I got 125 high; 65 - 70 low.
According to a couple of manuals, this vehicle's low side should be 34 to 37; high, 228
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