1990 K5 A/C problems

[FwDOFFROAD01]

the system currently in the truck appears to have been converted to r134a. whether it was done correctly or half a$$ im not sure, meaning all components replaced and system completly flushed. so i had the accumulator, compressor, filter, and hoses replaced and recharged by a so called mechanic and the ac lasted for 2 days at best. my first thought was there must be a major leak in the system. i then fount the hose going to the accumulator low side came off by hand and the o-ring had been over tightened causing it to extrude and slice. thinking this was the only problem why it was leaking i went ahead and replaced and installed properly, and began evac and recharge process. wasnt able to pull a vacum due to the fittings on the pump being too small to fit the yellow aux hose of the gauges. so i just went ahead and added 3 cans at 12oz or 2lbs give or take. the compressor immediately started to short cycle and fill the system. the cycles as the pressure increased as well as freon started to become longer until the 3rd can it finally just stayed on and blew ice cold while succesfully maintaining 40psi on the low side. i had the high side off the entire time while filling and never read any readings although once finished i detatched the QC fitting and it had what seemed like maybe 100psi or more behind it. so thinking that it was fixed and ready to go i went home and called it a night. the next day, i went to add 2oz of ester oil to the system for added reassurance and began setting up. hooked all gauges back up and turned max a/c on. the compressor was short cycleing again once i turned it on. and seemed as if it wasnt going to stop. i thought S%*t!! i didnt fix the leak. so frustrated i looked at the gauges and the low side still read 40-45psi????? yet the ac was not getting cold. so any help you guys can give to get this thing going so i can beat some of this texas 100* weather would be greatly appreciated!
thanks

 

[Fordum]

Oh man, there are so many things.....
First, are you sure you are using the gauges right?
You should have been reading something on the high side.
If there is air in the system, it can cause what you are seeing.
You need to get a gauge on the high side NOW. If there is a blockage, you could blow a hose or ruin the compressor.

I hate to say it, but since we don't know what is in the system at this point, eventually you will have to pump it down and pull a vacuum on it.

But, before you do, I think we can assume is does have some Freon in it, so now is the time to do a leak test.
If you don't have an electronic leak detector, you need to borrow one. Some parts houses will rent them I think.

So, first, try to find any leaks with it switched off. Then, hook up a high side gauge, and crank it up.
If the pressure stays sane, >300# or so, then check the high side for leaks while it is under pressure.

Also watch the low side to see where the compressor is kicking on and off.

Make sure the engine fan is working right. That can cause high pressures with no cooling.

Once you have all the leaks found and fixed, then you can put on the vacuum pump and let it run for a couple of hours.
Then turn it off and see if the system will hold the vacuum. If not, then you are going to have to find that leak.

After that, you can start thinking about recharging it.

 

[TheBeast_88K5]

Fordum needs a theme song...

 

[FwDOFFROAD01]

im sure i used the gauges right when i recharged the system. meaning once i primed the aux line, opened the low side valve, and kept the high off the enitire time. if that is improper then yes i did it wrong for sure man. i didnt even think of trying to read the high side in fear it would communicate with the low side or something would happen. so first things first is to get a reading on the high?
thanks for the response fordum!!!

 

[Fordum]

If you are using a regular charging manifold, then the gauges read all the time, but the hoses are not hooked to anything other than the gauges until you open a valve on the manifold.
Anytime you are working with an air conditioner system, you really need to watch the high side.
If there is a blockage, such as in the drier, or the orifice tube, that compressor can crank up enough pressure to blow a hose off in your face, or break the crankshaft in the compressor.

Just remember, when you do open the valve on the manifold, that line is then hooked to the input line.
I saw a regular " one pound " aluminum can of freon turn into a perfectly round softball sized ball because it got tied into the high side.

I was not even working for that shop. I was fixing a piece of their equipment and was walking past the car to get a part out of my truck, when the mechanic said, " look at that".
I saw the can bulging, and tackled him to the ground, just as another guy dove in and switched off the car.
That was the only reason it didn't blow.
Those cans have a blowout port, but that hot liquid can do some serious damage anyway.

Everybody made a big deal of me knocking the guy out of the way before it blew up in his face.

I didn't have the heart to tell them he just got in my way as I was diving out of the way.

 

[Fordum]

Fordum needs a theme song...

Funny you should say that. I have considered that myself many times. Some people have suggested this.

But, I am never sure which one they think I am..........

 

[FwDOFFROAD01]

so immediately go and just hook up the high side? and take a reading? or both high and low?
thanks

 

[Fordum]

Both high and low. Make sure the valves on the charging manifold are closed, and see what kind of pressures you see when its running.
If the high side goes over about 300, shut it down.

 

[PWagon]

K5 A/C Problem...

I just round-and-round with my A/C on my 1986 K5. Let me share with you a little pearl of wisdom it took almost 5 years for me to figure out. Long story short, your A/C system will blow air to the path of least resistance. You have two possible air leaks under your hood (the 2 coolant lines going into and out of your air box). If you truck is like mine, the putty the factory installed has long been cracked and leaking. Mine was completely gone, thus dumping my cold air into my engine compartment. I spent countless hours and spent a lot of money having "professional A/C guys" to look at my system. No one ever looked to see if air was leaking out of these two places. I finally stumbled upon it. I used plumbers putty (found at Lowes / Home Depot), and bingo... my A/C now blows a lot harder. Keep in mind that this will not make the air colder, but it makes all the forced air go into the cab and not the engine compartment. I genuinely hope this helps you and/or anyone else who reads this. Good luck and stay cool this Texas summer!

 

[4xcrazy]

Check the valves, the past few I have worked on for friends have had the service valves leaking.

 

[FwDOFFROAD01]

thanks fellas for the help im going to look into all avenues to get it going.
and pwagon yes mine is dumping air as well around that black/tar looking stuff as well.