At my wits end with my a/c!

[4xcrazy]

Your return will create some frost on it, all ac systems I have ever seen working good always do that and just because the compressor isn't cycling doesn't mean it's overcharged, it can mean the system is stabilized enough to use what's in there to be adequately charged and pressurized to MAINTAIN normal operation.

The one in our Avalanche hardly cycles when it's up on high, it will when down lower though. normal.

You should have left it alone before bleeding off the extra you thought you had, sounds to me like it was working fine at that point.

 

[SouthernYank]

You'll have some frost, it's not uncommon. As far as the pressures in that system, I couldn't tell you I'm sure someone on here knows though. That seems to be a decent temperature split 66/40.

Roll with it like that for a bit and see how does.

 

[Blue85]

So I went and purchased the proper clutch cycle switch and installed it. It cycled on and off accordingly, but too frequently.

the return line to the compressor was freezing up and the switch didn't cycle off. ... Still making 40 degree air at center vent. It did not appear to freeze up the return line. Who knows what the 134a charge is at this point!

This sounds a lot better. The line should be cold all the way to the compressor. That's actually one way to set your charge - keep adding until it's cold all the way through. It's normal for the compressor to run near 100% when the vehicle is sitting. It's once you're driving around that you get enough refrigerant flow and air flow to cycle it off. Typically a lot of cycling at idle means refrigerant is low.

Oh yeah, the stock pressure cycling switch is adjustable! You can use the gauges to set it just above freezing.

If the coolant temp keeps getting high, it is probably an issue with the cooling system, not the A/C.

 

[elyon]

Ok, one last question and then I'll quit. Condensation forms on the return line and freezes up right before the compressor. Not at the accumulator or any place prior to the rubber section of line. Only at the compressor. Not always either. Is this ok? I am so gun shy at this point. Could it just be cooling air from the fan causing it to freeze up? There is no air flow over the section of line that does not freeze up. I don't want liquid freon to enter the compressor and destroy it.

 

[Blue85]

The whole low side should be cold while running, which is everything from the orifice tube to the compressor. Sometimes the receiver/dryer does get cold, but that depends on a lot of factors. There is liquid refrigerant moving through there, but the pressure may be high enough to keep it from boiling. It's the boiling of refrigerant that "makes the cold". The compression of it "makes the hot".

 

[elyon]

Let me rephrase my question. Will frost forming on the suction line just prior to the compressor cause liquid freon to enter the compressor.

 

[blazer74]

Let me rephrase my question. Will frost forming on the suction line just prior to the compressor cause liquid freon to enter the compressor.

If your low side pressures are good thats your indicator. If you had a blockage or restriction in your low side , low side pressure will go up .
How much 134 do you have in there and What are your pressures?
What is your cycle switch set at?
What are your outlet temps

A/C kits.Com has good info and a forum.

 

[elyon]

Last reading was 30/151 70 degrees 66% humidity making 40 degree air in cab. Honestly, I messed with the charge enough that I am not sure how much any more.

 

[y5mgisi]

Good a/c tech! Subscribed!

 

[blazer74]

Your fine for now, leave it alone till it gets hotter out and see how it does, your not over charged. Usually if your outlet pipes from evap are the same temp as the inlet pipes or slightly colder your good.

Overcharged you'll loose cooling and high high side pressures.
Undercharged poor cooling O tube or exp valve will frost up prior to evap and low pressures.

 

[blazer74]

 

[SouthernYank]

blazer74 has some good info, I agree your pressures look good and you'll know once it heats up if there are any issues with the amount of charge. These systems usually show their bad side once things heat up real good.

I've worked on mini splits here in AFG for a while (not so much anymore) but they all seem fine when ambient is in the 60-70 range. Then it gets up around 117+ ambient and all hell breaks loose...... litterally!

 

[Fordum]

Let me rephrase my question. Will frost forming on the suction line just prior to the compressor cause liquid freon to enter the compressor.

Its not uncommon for the return line to sweat all the way back to the compressor.
BUT, frost at the compressor is dangerous. Frost is almost always boiling freon, which means there is still some liquid there.

I personally never like to see frost close to the compressor. On a cool day, frost at the output of the evaporator and even some on the accumulator if your truck has one is not bad.
It will go away on warm days.
If you have frost almost to the compressor, it would be best to either adjust the pressure switch to have it cut off quicker, or remove a small amount of freon.
Otherwise you might hear a sudden squealing one cool morning when the belt starts slipping on a seized compressor.

A good rule of thumb for home ACs is a 20 degree differential between air into the system and air out of the system.
This gives good cooling and lets the system take a lot of the moisture out of the air.
In a house, you want the air to pass through the system more than once per cycle so that it takes more humidity out.

Auto ACs can go a little more, because the air volume is less. But, I would shoot for about 20.
Remember its the air going into the system that you compare the output with.
If the truck is on recirculate, you measure the temp going into the evaporator and compare it to the air coming out.

 

[blazer74]

A stand alone cold spot could indicate a blockage acting like a second o tube. If that was the case it should cause the low side pressures to be higher. Set your cycling switch to 21-22 psi.
If your not comfortable take it back apart and check it the inlet to compressor for debree.
If your not sure how much juice is in there and not comfortable start over and recheck all including O tube.