AC Rejuvenation?

[Big T]

Alright, need to rejuvenate my AC on the '99 Burb, so where do I start?

I suspect I have a leak. So how do I check it?

I just received the following parts order:

* AC Vac Pump

* AC flusher

* AC PAG Oil with UV Dye

* UV leak detecting light

* VOV

* New accumulator/dryer (AC Delco...Made in China)

* RC 134a Gauge Kit

Need AC Flush and 134a refrigerant.

So where do I start, what do I do and how do I do it? Please describe for the simpleton.

 

[Acesneights1]

for all the money you spent on tools you could have just had someone do it..
I don't generally flush the system unless something came apart or it was left unsealed but that is me. They make ac flush . it's pricey and is the same thing as denatured alchohol. Really up to you. I'm cheap so I use the alchohol.Take the drier off and disconnect the lines from the compressor. Pull the orifice out also and flush all the lines and condensor. Make sure what ever you use you get it all out and make sure your air compressor that your using has a water separator or atleast drain the tank. Nothing like blowing out an ac system with a compressor that's full of humidity and water.
DO NOT FLUSH THE COMPRESSOR OR DRIER.
What was wrong with the ac system that you felt the need to do all this ? Just curious ? Was it working at all or was it butchered ?

 

[Big T]

for all the money you spent on tools you could have just had someone do it..
I don't generally flush the system unless something came apart or it was left unsealed but that is me. They make ac flush . it's pricey and is the same thing as denatured alchohol. Really up to you. I'm cheap so I use the alchohol.Take the drier off and disconnect the lines from the compressor. Pull the orifice out also and flush all the lines and condensor. Make sure what ever you use you get it all out and make sure your air compressor that your using has a water separator or atleast drain the tank. Nothing like blowing out an ac system with a compressor that's full of humidity and water.
DO NOT FLUSH THE COMPRESSOR OR DRIER.
What was wrong with the ac system that you felt the need to do all this ? Just curious ? Was it working at all or was it butchered ?

Yeah, but I have to do two trucks and a few cars. I've got denatured alcohol.

AC was not working at all. Compressor clutch was not cycling on until I put refrigerant in. Got compressor clutch to cycle on, but no cooling whatsoever. The dryer never got cold. So I assume I'm starting from ground zero. I need to check for leaks, etc. I'm into this for $200 of equipment, but that's not counting the last load of refrigerant. If I took it in and it needed a new compressor and all that, I'd be hosed. Plus, I am determined to do this myself. Forced learning curve you know.

 

[JMJNet]

Have you changed the low pressure switch? Easy it is the one on the Dryer with electrical connector.

I am not sure on the 99 but the compressor is usually the weak part in the system.
At least that is what I heard.

 

[Big T]

Have you changed the low pressure switch? Easy it is the one on the Dryer with electrical connector.

I am not sure on the 99 but the compressor is usually the weak part in the system.
At least that is what I heard.

No have not change the low pressure switch, but did short across the plug terminals to get the compressor to cycle on while filling it with refrigerant.

Again, I know virtually nothing about AC systems and I'm looking for the AC for Dummies guide here.

 

[JMJNet]

I don't know too much either. Last time, I put it in a shop specializing with AC. They run the ACDelco AC supply here. After changing everything, things still did not work correctly (not cycling properly), after further diagnosis, they changed the Low Pressure switch and everything is good.

Most of the time though, the compressor is gone if you don't have pressure.
I could be wrong.

 

[Big T]

I don't know too much either. Last time, I put it in a shop specializing with AC. They run the ACDelco AC supply here. After changing everything, things still did not work correctly (not cycling properly), after further diagnosis, they changed the Low Pressure switch and everything is good.

Most of the time though, the compressor is gone if you don't have pressure.
I could be wrong.

My experience was limited to the '95 with the compressor going out 3x, the last 2 dealt with under GM's lifetime warranty. In each case the compressor went out, you can hear a loud knock over and above that of the engine. I hear nothing when the compressor cycles on. I'm giving the compressor the benefit of the doubt. I will go buy a low pressure switch.

 

[Acesneights1]

Most of the time though, the compressor is gone if you don't have pressure.
I could be wrong.

Or the orifice/expansion Valve is shot. Or there could be a blockage.

 

[JMJNet]

Or the orifice/expansion Valve is shot. Or there could be a blockage.

That is a lot more difficult to change. Try the easy one first.

If that is not the case, then go to AC mechanics or go to stealership and get a lifetime warranted compressor.

 

[iamdave0887]

I'm in the process of doing this with my Blazer's R-12 system right now.

Change out the parts that are regular replacement items(Accumulator, Orifice tube). Also purchase the O-ring kit. you don't have to get one of those "200 piece o ring assortments. The kit i bought from advance auto was ~$6 and had all the o-rings i needed for my system.

Dip the O-rings in the oil you are going to use with the system before you install them. Since i'm using R-12 i'm using a mineral oil. With 134a you'll be using PAG oil.

Make sure you find out how much oil you have to add to the system. My compressor said "refrigerant oil - 10.0 oz". however only 6 of that 10 was in the compressor and the other 4 was to be distributed about the system. I poured 3 oz of oil in the evap top opening, and 1 oz of oil in the new accumulator, giving me the 10.0 of oil needed.


The accumulator is installed last as it has a desiccant in the bottom that's used to absorb moisture in the system. If you install that first and leave the system open to the air, that desiccant is going to try to absorb the moisture from the air, and it can't, so it becomes full and can no longer absorb moisture from the system once it's been closed again.

Once your certain that the rest of the system is all intact, install the new accumulator, making sure you use new O-rings with it. My ACDelco accumulator came with new o-rings but i used the ones that were in the o-ring kit as they looked to be better quality.

Now that the system has been sealed up, it's time to use your vac pump and gauges. Does your set of manifold gauges have a vacuum reading on the low side gauge? I know the old set I'm using does, and i'd figure most good quality ones will, but the cheapie's they sell at the auto parts chains do not.

Hook up the manifold gauges low gauge hose(blue hose) to the low side service port. Hook the yellow hose to the vac pump. Follow the procedures to start the vac pump after you check and make sure the oil(if it uses any) in the vac pump is full. Some you can just plug in and it's running. The one i'm using is oil-less so it's just plug in and go. Once the vac pump is running, open the low side gauge to the yellow hose by turning the hand wheel near the low side gauge. This will open the system to that yellow charging hose, and you should see the gauge start to read vacuum immediately. Mine dropped to 10 In of Hg instantly and continued to head towards 30 in of Hg. Once the gauge stops moving, close the hand wheel to isolate the A/C system again, and shut down the vac pump. Let it sit for 5 to 10 minutes while listening for leaks. If you've got a leak, the vacuum in the system will drop, and you'll see that on the gauge. If the needle doesn't drop after 10 or so minutes, re start the vac pump and re-open the hand wheel and let the vac pump run for at least 30 minutes. I let it run for about 45 and then let the vacuum sit in the system overnight to make sure it's not leaking at all, since R12 is not something you waste anymore considering how expensive it is.

Once you've run the vacuum for at least 30 minutes, close the system off again at the hand wheel, and shut down disconnect the vac pump. Your done with the vac pump so move it out of your way.

At this point you can start to charge the system. You can hook up the high side(red hose) if you haven't already, but do not open the hand wheel. The pressure in the high side line when the compressor is running(during charging) will cause the can to burst. You'll be using the high side gauge just to check for pressure in the system.

Hook up a can of refrigerant to the can tap but make sure the pin is all the way up into the can tap first. Tighten the can tap by hand. install the yellow hose onto the can tap. Now you'll want to pierce the can with the can tap once all the connections are tight. Rotate the can tap all the way until it's bottomed out. The can is pierced, and you cannot remove the can tap from it until the can is empty or the contents will be released to the air.

Open the low side hand wheel once again and then rotate the can tap so it's all the way up. Follow the instructions on the can for charging. Most can's say to rotate between 12 and 3 o clock while shaking the can. I just tend to rock the can back and forth from 12 to 3 and that works. Once the can feels empty most will say to hold it upside down for 1 minute to make sure it's empty. Once that's been done, close the low side hand wheel, close and remove the can tap from the yellow charging hose. remove the can tap from the now empty refrigerant can. you'll still get a slight hiss from any "empty" can, so don't worry about it.

Repeat the portion in blue above until you've installed the correct amount of refrigerant(go by weight listed somewhere on the system) and the pressures, both low and high, are in the correct zones.

 

[Missy Good Wench]

With a system that is leaking, I like to shoot in enough 134 to get the thing to cycle, then with the system shut off, use an electronic sniffer and search for leaks.

Two very common places are the hose crimps (where the aluminum tube connects to the hoses) and the high pressure safety switch. (can leak where the wires plug in)

The UV light/dye system will not show small leaks of gas only. The UV dye only shows of there is oil escaping.

Replacing the accumulator is a great idea while the system is apart.
Replace the orifice tube just to be sure its not damaged or the screen plugged.

Add about 4 oz of oil to the new accumulator (big solver can over in the corner) before you install it.

The desicant material inside the can absorbs quite a bit of the oil.

Check the compressor clutch area well with the sniffer, especially if there is any oily residue around the clutch area.

Carefully sniff the area near the floor vents inside the truck.

These can indicate a false positive if there is moisture in the evaporator.

Another spot that can and does have leak issues is the connection couplers for the low and high sides of the system.
The schrader valves go south and will leak. Soap solution applied to the area with the little plastic caps off will show any leaks.

These connectors have a hex on one end and can be removed with a 6 sided socket.

My gut feeling is a leak in the hose harness, a schrader valve or compressor seal.

Once you find and repair the leak, evacuate the system to 29"hg for 30 minutes or so to remove any moisture.

Close the lowside valve as well as the highside valve on the gauge set.

Unhook the vacuum pump, connect the pail of 134A AND OPEN ITS VALVE.

Now before you open the low side valve on the gauge set, carefully unscrew the feed hose from the paol of 134 until it just HISSES. This will purge any air from the line.

Now open the LOW SIDE VALVE only and allow 134 to flow into the system.
Start the engine and set the AC system on max air with blower on full.

Let the system cycle and watch the gauges. Once the cycling settles down to a slow pace and not ON OF< ON OFF real quick you will be getting close.

The High side pressure should be around 155-200 PSI and the low side (with gauge valve off) should drop to around 40 possibly a tad lower when compressor is running.

Air temp at the vents on a warm day (80 or so) will fall to around 45F .

Long periods of idling will see the temps rise some. Have a helper run the RPM to around 1500 and keep it steady.

This will allow the fan to get enough air through the condenser and to maintain good refrigerant flow.

Once the cycle times are reasonable and the air at the vents is cold, stop filling as from that point you can easily overfil the system and cause it to STALL due to liquid refrigerant reaching the compressor.

Having a good acurate scale to weigh the bottle and then add just the prescribed amount is the proper way but, I have never owned a scale so just always fly by the seat of my pants.

Always works well for me.

Good luck and keep us posted.

Missy