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A/C Chargers - Good or Bad?

T

TurboTahoe

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Hi guys,

OK, I know this isn't really 6.5 specific, but the Tahoe has a very very slow A/C leak. It takes about 2 years for it to leak down to where it needs a recharge, so I really don't worry about it that much. Last time, the dealer did the evacuate and recharge, cost about $200 (!)

Well, it was about 2 years, and sure enough, 1st warm weather today, and the A/C is just kaput. The compressor cycles on and off, but no cold air. Last time, they just did the regular service and added some ultraviolet dye to try and figure out where the leak was. They wanted me to return after 1 week for a 'checkup'. I didn't want to spend another $100 for a 'checkup', so after 1 week I took my ultraviolet lamp out there and checked all the obvious spots 2 years ago, but found nothing. It ran GREAT for 2 years, no weirdness at all. Just good old' GM A/C, nice and cold (at least that is ONE thing GM does well - the A/C system is great.)

Anyway, things are tight financially (who isn't holding their breath these days?) and I was at the auto-parts store and saw the A/C recharge system (the ones with 1 lb of refrigerant and a cheapie gauge on the top) on sale, so I sprang for the $20. Followed the instructions, and it was pretty easy to get it up to 35 lbs of charge.

Question after the fact - are these kits in any way harmful to the A/C system? I remember studying A/C systems in High School, and they are pretty simple, and I really can't think of any negatives to using this kind of el-cheapo system, other than you didn't do a proper evacuation and have less gauges, etc. The can says it has oil in it already as well as some kind of sealant in addition to the refrigerant.

Any opinions? Facts? Smart remarks? If I have done a bad thing, I suppose I can always go to the local A/C shop and have it redone professionally.

-Rob :)
 
I've used the same kit the only problem I had is with the guages I actually overfilled mine even though the guage said it was fine. It made all kinds of noises and occasionally vented some freon but finally stabalized and worked fine.
 
TurboTahoe said:
Hi guys,

OK, I know this isn't really 6.5 specific, but the Tahoe has a very very slow A/C leak. It takes about 2 years for it to leak down to where it needs a recharge, so I really don't worry about it that much. Last time, the dealer did the evacuate and recharge, cost about $200 (!)

Well, it was about 2 years, and sure enough, 1st warm weather today, and the A/C is just kaput. The compressor cycles on and off, but no cold air. Last time, they just did the regular service and added some ultraviolet dye to try and figure out where the leak was. They wanted me to return after 1 week for a 'checkup'. I didn't want to spend another $100 for a 'checkup', so after 1 week I took my ultraviolet lamp out there and checked all the obvious spots 2 years ago, but found nothing. It ran GREAT for 2 years, no weirdness at all. Just good old' GM A/C, nice and cold (at least that is ONE thing GM does well - the A/C system is great.)

Anyway, things are tight financially (who isn't holding their breath these days?) and I was at the auto-parts store and saw the A/C recharge system (the ones with 1 lb of refrigerant and a cheapie gauge on the top) on sale, so I sprang for the $20. Followed the instructions, and it was pretty easy to get it up to 35 lbs of charge.

Question after the fact - are these kits in any way harmful to the A/C system? I remember studying A/C systems in High School, and they are pretty simple, and I really can't think of any negatives to using this kind of el-cheapo system, other than you didn't do a proper evacuation and have less gauges, etc. The can says it has oil in it already as well as some kind of sealant in addition to the refrigerant.

Any opinions? Facts? Smart remarks? If I have done a bad thing, I suppose I can always go to the local A/C shop and have it redone professionally.

-Rob :)
Click to expand...

i bet it's the compressor shaft seal leakin'....had to put freon in the burb 2 to 3 times when it was hot out and would run out over the winter....got up to 75f last week and it blew just as cold as the day i changed the compressor....last fall...
 
No need to evacuate the system if all you want to do is add charge. Those quick charge systems you get at the parts store are fine as long as your system already has R-134A in it. If your truck is old enough to be R-12 then obviously you don't want to add R-134A to that.
 
the only real issue is that you need to make sure you tell the next shop that touches it that you have a blend in there, cause it will write off their recycle tank.

other than that go for it
 
There OK, just don't use the ones with additives in them. Don't go adding oil or stop leak to it. The stop leak WILL cause problems eventually, and adding oil if it doesn't need it will result in high pressure with poor cooling. I give youy a 90% chance your leak is the high pressure port for the guage hook-up. These are a known leaker, and a crappy design to boot. Both GM and FORD used them, and they are normally the leak point for a slow hard to find leak. The new charge port isn't expensive, but if you don't have a pump to evac the air afterwards don't change it. Also always keep the charge low on those cheapo charge guages. A/C pressures are not a pre-set number like household A/C's. Every system has it's sweet spot, and it could be anywhere from 10-75 on the low side and 150-275 on the high side. R134A is also a pain to charge as it changes pressure so much with ambient air temp.

An easy way to charge an R134A system is to get the engine up to temp and run the system for about 5 minutes on MAX on a day with an ambient air temp of 80 or higher. Go out and feel the low side suction line at the compressor. It should feel cool or cold with a little condensation on it. If it's warm add some charge a little at a time until it feels cool to slightly cold at an idle. This will get you close on the charge without a guage and most of the time will be almost dead on. The goal is to get a solid vapor stream to the compressor, BUT NO LIQUID!!! You want just enough charge in the system so that by the time the refrigerant leaves the evaporator it has changed from a liquid to a gas. If the line is warm then that means there is hardly anything in the line, whereas cool to chilled will mean a good vapor to it. Ice on it will mean liquid is in the line and compressor death will soon follow.

Also make sure your engine is up to temp enough so that your fan clutch is pulling some air through the radiator and condenser. Many people undercharge an A/C because they don't get everything up to temp before charging. When the fan clutch disengages like on a cold engine after the first RPM increase, your high side pressure will skyrocket if your not moving and throw your charge off.
 
I recharge mine for about 2 years, finally, it would not charge anymore. Give up and pay somebody to change the compressor out. It is expensive but it seems to work now. Another weak point or may be aging is the switch (I am not sure what it is called) that is on the dryer. It controls the on-off cycle of the AC.
 
I'm pretty sure all auto AC systems were R-134 by 1995. Most were by 1994. At any rate, the refrigerant should be clearly labeled under the hood somewhere. If you bought a R-134 kit, and it fit your lines, then you got the right stuff. R-134 adapters are different than R-12.

You need to get a set of gauges and charge by the high side gauge. Charging by the low side gauge isn't going to do you any favors. As long as you only put in R-134 (and maybe a little oil), you should be okay. You need to charge so the inlet and outlet of the evaporator are about the same temperature (cold). ...but you need to do so without going too high on the high-pressure side. Add a little oil if you've refilled it before. If it's been evac'd and recharged and this is the first leakout, you should be okay without any oil. I'd probably add an ounce or two of oil anyway. The danger of charging by low side pressure is that you can overcharge it. If that happens, the release on the compressor will let go -- probably while you're sitting at a traffic light on a hot day. It should burp, and then close back up. I'm not sure when they started putting high pressure cutouts, but if yours has one, it will just shut off the compressor when the pressure gets too high instead of venting the overcharge to the atmosphere <sarcasm on> and releasing all that evil greenhouse gas <sarcasm off>. My old Burban just has a burp valve on it.

You should be able to see an oily residue wherever it's leaking. If you can't, you might suspect a leaky evaporator.

I had nothing but trouble with the R4 pancake compressor in my 91 Suburban. I ended up with a new one after getting 3 leaky rebuilds.
 
Last edited:
Any R-134A system should have the high pressure cut-out instead of the vent. The EPA started this when R-12 was phased out.
 
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