'97 Suburban - Dual A/C Question

My 1997 Suburban with dual A/C blows cold in the rear but not in the front, and because nobody has ever touched or charged the A/C system since 1997, I suspect that the system finally needs some refrigerant..

Additional symptom:
Compressor cycles ON/OFF every 5 seconds or so, which I interpret as an indication of low refrigerant level. I have turned the air OFF immediately as I saw that fast cycling of the compressor.

The main question is:
Looking at the picture below, which port do I use to charge the FRONT system?
I see 2 ports, marked [1] and [2] in the picture. I want to be 100% certain that I am using the correct port for charging.

Thank you in advance!

http://www.market-place.com/intake/ac.jpg

I think the hose will only fit one of the adapters/ports, which I think is number 1. I had the same problem with my 96 suburban last year the rear was colder than the front so I put 2 cans in and it fixed it. Someone will chime in and confirm it I'm sure.

Interesting. I haven't even opened and looked under the two black caps to see if the two adapters look the same or not. I guess I'll have to look. Until now, I thought they were identical.

The caps are the same size (same internal thread) - the port ODs are different- the one you will attch to is the one on the right (#2) as it is the smaller of the two ports- and is the low side suction port that comes from the accumulator- just outside of the evaporator- Yes you need refrigerant- due to a leak- number one leak location on your system is the compressor belly- look under it- is it oily/greasy- if so you may consider a pump change- depending on th esize of your leak....also the rear lines can corrode at each grommet- under the truck along the frame rails......Again- watch for oil/greasy build-up on those-- I assume yours is a factory rear air system-- most aftermarket systems are strictly rubber hoses that run to the rear.....

Those symptoms are typical of a system a little low in R134a refrigerant. In 12 years, one would expect some loss; it's designed to leak a little, out the compressor seal, to keep the seal lubricated. I personally caution about just adding refrigerant with a single hose- and NEVER (NEVER means NEVER) - use refrigerant that contains additives like leak sealers or seal restorers: junk. R134a refrigerant only, only other accepted thing to add would be a little UV dye). I would use a traditional gauge set up so you can monitor both low and high side pressures (follow instructions), the fittings are different sizes so you can't screw them up. You may need 1 to 1.5 cans, but you really need to monitor the gauge pressures to get it right, unless a shop pulls out all the refrigerant and re-adds the correct amount by weight. Generally, you want high side pressures about 250 psi, low side about 30 to 40.

I always love it when people say it is designed to leak a little-- try telling that to your automotive platform customer!!! GM, Ford, Honda, Toyota, etc don't won't to hear that!!! They will go to someone who can make a compressor that doesn't leak..

The leaking shaft seal theory by design may have worked 25 years ago with the old ceramic/carbon seals (circa 1984 and prior)-besides no one purposely designs a leaky seal- they fight them all their life... and many a mechanic has gotten away with a simple recharge by claiming the leak is normal. But with the advent of the double lip teflon and rubber seals- the seals are self- lubricating and no leaks are to be expected.. my two year study of shaft seals revealed that the old wive's tale of "it leaks by design to lubricate the seal" no longer applies.

I would bet the OP's shaft seal (double lip OEM design) is good- just he has a belly leaker in the making......or a rear line corrosion leak....seen a bunch like that.

First thing do not even think about one of the Walmart one hose one gauge death kits.

Only recharge with the proper ac recharge gauge sets and pure R-134a.

As said look for leaks but leak off over 10-12 years is not bad.
A lot of systems will seap off in winter or have cold weater seaps.
There is a R-134a fitting on the low side line for adding r-134a.
But first you need one of these type gauges to check your low and high side pressure readings.
http://www.ackits.com/merchant.mvc?Screen=PROD&Store_Code=01&Product_Code=66773&Category_Code=RefrigerantGaugeSets


http://www.ackits.com/merchant.mvc?S...erantGaugeSets

Do not even think about one of the Wal mart one hose death kits.
Check your low and high side pressure readings at idle and at 2K rpm and post back pressure readings.
And remember if it is low or you have a leak you need to fix the leak first.
The newer systems it is very hard jst to add freon and get it right.
The system should be pumped down with a vacuum pump and the set R134-a charge added

http://www.ackits.com/merchant.mvc?Screen=PROD&Store_Code=01&Product_Code=66773&Category_Code=RefrigerantGaugeSets


A link on ac sealer crap.
http://www.autoacforum.com/messageview.cfm?catid=2&threadid=15719


Walmart deat kits are a no no.
You cannot properly and safely recharge an air condition system with them.

The one side stop and go gauge does not tell you what your system is doing or is over charged or undercharged.
A overcharged or malfunction air condition system can reach over 500 lbs of pressure.
Enough to blow up that can or system and freeze you at first and the burn you or blind you and if any propane /butane in there blow and light you up.

The stop leak crap and who knows what kind of oil in the kits there will stop your system for sure.
Just like pouring super glue in it.
And some kits even contain freon with a butane mixer.
Good for a big blast.

If you are going to do it do it right and safe.
Here is what you need to start with.
http://www.ackits.com/merchant.mvc?Screen=CTGY&Store_Code=01&Category_Code=RefrigerantGaugeSets

In the older days you could just throw in a can and go.
But over the years just adding freon is getting harder to do.
Newer systems have to have the correct amount of freon down to the ounces.
Most will need pumped down and vacuumed down and the right and amount of oil and a set amount freon charge installed to get the air to cool right and the system to last.
If an air condition is low there is usually a leak that needs fixed and also a lose of lubricating oil from system.
Also air and moisture enters a low system
If you are going to try to do it get the proper type air condition gauge set with the low and high side gauges.
Hook up the gauges and get a reading with compressor running at idle and at 2000 rpm on the high and low side.
Post back pressure reading and we can help you.
MT

Thank you all for this great input!

Honestly, I have heard this "leaking is normal over such a long period of time" before, and whether it does apply to my 97 Suburban or not, there is still the fact that my system is low on refrigerant, no doubt about that. I am still super-proud of my Suburban making it this long with the original charge, really! There could be a plethora of reasons why ..or why not.., but I think the heaviest one on my list may be the fact that I have moved to Canada from Florida two winters ago. Who knows, maybe two winters did something to it, maybe I haven't used the A/C as I used to use it in Florida, and maybe because I left the vehicle sit one whole winter outside in a parking lot while living in an apartment?!? All speculations, I guess. Yes, everything but the stereo system on this truck is factory original equipment.

Thank you for the advice NOT to use the one-hose fill gauges from WM, and specifically MT-2500 for providing these great ackits.com links. As anal as I am about doing it right the first time, I will take my time and definitely do it right with the right stuff. This forum has helped me before with my intake manifold gasket repair, I totally trust your opinion. I will order me one of these double gauge "toys". I am not that much of a pro to go digital, but the cheaper analog will do just fine. It is still cold in Ontario, it just snowed for two days.. no need to hurry with the A/C, and I am a very, very patient fellow :smokin:

I'll keep you posted and as soon as I get the right equipment I will post some numbers.

Again, many thanks to all in this thread!!!

Just to add to your post. It cost me $114 to evacuate and charge my '98 Sub A/C system professionally with a dye that can detect leaks. I am a gear head but I won't mess with the A/C system on my own.

You are welcome and let us know how it goes.
Good luck

Check your compressor first before recharging it. The OEM compressors are known as "belly leakers" due to a design problem. Suggest you Google "HT6 Belly Leaker" to find out more.

I replaced the OEM compressor in my Suburban and Tahoe with a Sanden HT6 bought from "alaskaflorida" on eBay for ~$200

If you are going to replace the compressor, make sure you replace the orifice and the dryer at the same time,

I've dealt with both ACkits.com and ACSource.net in person, as they're in my city, very dependable. Again: I'd get an R134a gauge set first, read the pressures once it gets warmer outside. You live in Canada, not here in Arizona, so your system gets tons less use than those here, and your parts should last longer. You may find that all you need is some R134a. The point is: you need to check the pressures, anything else is working blind. Now, if you end up swapping out a compressor because of a slight leak there, but the system still hold pressure, you may not really need to swap out the orifice tube and the accumulator (what someone terms a drier); they don't cost that much, but sometimes the metal threads on connections on these Suburbans can gall after all those years and cause their own problems with dis-assembly/assembly.