Air Conditioner Not Working...

[xzz0195]

Last week I added R-134A to system. Followed instructions... Turn on AC to Max, attach meter, look for proper pressure, add until pressure is in proper zone as indicated on meter... I believe that the "Green" zone topped out at 45PSI.

 

So I did this, getting it to top of "Green zone" or 45 PSI.

 

Tested truck, was as cool as I've ever felt it... Subsequently, I thought I'd recheck the pressure and it was now in the "Alert" zone, above 45psi. I attempted to relieve some of the pressure, but didn't have great success because I didn't have proper tool. I didn't understand why pressure would have risen like it did...

 

Two days later the unit doesn't cool any longer. So I hooked up meter and now it shows nothing. I tried to add more stuff, but the refill kit was now acting as if there was no way to put stuff into system. As if the inlet was not opening when attaching the tool. The can was now leaking out the hose fittings prior to entry into system. I tried tightening, no go... I cannot get any R-134A into the system... Needless to say there's no cooling...

 

What did I do wrong, how do I correct? Did I kill the compressor?

[ken1mod]

Sir,

 

With all due respect. You should not be working on equipment you don't know enough about.

 

If your unit gets cold, it is working fine. Low side pressures vary constantly in normal operation. They rise when the system is off. The best test for a/c is whether it gets cold or not. Stop messing with it.

 

I say this respectfully.

 

Ken

[xzz0195]

Sir,

 

With all due respect. You should not be working on equipment you don't know enough about.

 

If your unit gets cold, it is working fine. Low side pressures vary constantly in normal operation. They rise when the system is off. The best test for a/c is whether it gets cold or not. Stop messing with it.

 

I say this respectfully.

 

Ken

 

I agree with you... I really wasn't trying to retool the system, just add a bit of 134A per our local Napa store that sold me the kit and told me it was easy to do. I followed all the instructions, but apparently killed the unit.

[ken1mod]

I don't believe you killed the compressor. If it lost its charge, there is a leak somewhere. Sometimes the shraeder (pin) valve at the service fitting sticks and leaks some.

 

What was the original reason you wanted to add refrigerant? Original problem that caused you to go to napa.

 

Ken

[dewfpo]

When you rechecked the low side system pressure and got the high reading, was the engine running and the A/C on?

 

DEWFPO

[xzz0195]

I don't believe you killed the compressor. If it lost its charge, there is a leak somewhere. Sometimes the shraeder (pin) valve at the service fitting sticks and leaks some.

 

What was the original reason you wanted to add refrigerant? Original problem that caused you to go to napa.

 

Ken

 

 

Ken;

The orginal reason was that on really hot days the air conditioner wasn't as cool as it was in past, I thought to add more 134A as a result. Guys at Napa encouraged me to giver 'er a try.

[xzz0195]

When you rechecked the low side system pressure and got the high reading, was the engine running and the A/C on?

 

DEWFPO

 

Yes, the AC was on with engine running...

[dewfpo]

Do your remember how far above 45 psi it was on the recheck?

 

Also,

 

Disclaimer : The proper way to recharge an R134a system is to reclaim all the old R134a, pull a vacuum of ~30" on the system, see if the system can hold it for 1/2 hour or more, if it holds (likely no leaks), then add the appropriate amount of R134a by weight and any PAG oil (in ounces) as required if components were removed.

 

That being said, the following procedure has worked well for me when doing a simple recharge when the system is just a little low. You can go to Wal-Mart or any auto parts store that sells R134a. Get a can of R134a and a separate pressure gauge. You will also need a thermometer that you can stick into the center dash vent.

 

Procedure : Open your hood, start the engine, turn the A/C ON, recirc - ON, fan on it's highest setting. Attach the gauge to the low side port on the receiver/dryer. The compressor should be cycling or ON steady. The pressure readings on the low side should be between 25-45 psi. The compressor will come on at 45 psi and go off at 25 psi.

 

If the pressures are in that range, then attach the can of R134a and open the valve on the can, now go into the car and watch the thermometer (you can raise the engine rpms up a bit if you want to speed things along). When the temperature stops going down, close the R134a can and remove it from the system. You don't want to overcharge a R134a system. Your done.

 

DEWFPO

[ken1mod]

Gentlemen,

 

A high low-side reading with the engine running at fast idle indicates an overcharge. Unless the weather is extremely hot, the system is designed to cycle on and off maybe every minute or so. If the unit were correctly charged, automotive systems are not as critical as a refrigerator, the unit will cycle off to prevent the evaporator, the thing that cools the air , from freezing into a chunk of ice and blocking air flow.

 

Again, these systems are simple for a/c units but you must have a pretty good understanding of how they work before you mess with them.

 

In general, if the system starts operating poorly but still cools a bit, and the accumulator is warm with the system on at fast idle, it is ok to add perhaps half a can of refrigerant unttil the accumulator gets quite cold. Too much refrigerant will degrade performance and more will stop the compressor and maybe destroy it.

 

Ken

[xzz0195]

Gentlemen,

 

A high low-side reading with the engine running at fast idle indicates an overcharge. Unless the weather is extremely hot, the system is designed to cycle on and off maybe every minute or so. If the unit were correctly charged, automotive systems are not as critical as a refrigerator, the unit will cycle off to prevent the evaporator, the thing that cools the air , from freezing into a chunk of ice and blocking air flow.

 

Again, these systems are simple for a/c units but you must have a pretty good understanding of how they work before you mess with them.

 

In general, if the system starts operating poorly but still cools a bit, and the accumulator is warm with the system on at fast idle, it is ok to add perhaps half a can of refrigerant unttil the accumulator gets quite cold. Too much refrigerant will degrade performance and more will stop the compressor and maybe destroy it.

 

Ken

 

 

Thanks Gents, I will post back some comments tomorrow on this. Appreciate your input.

[ken1mod]

It is normal for a/c units to put out warmer but still nice cool air when it gets very hot and humid. Humidity is seen by the a/c the same as heat. It is actually called latent (hidden) heat.

 

If your a/c condenses lots of water dripping from under the truck and the accumulator is cold to the touch, it is working fine. A warm accumulator is the first sign of an undercharge. Add refrigerant until the accumulator is cold and no more. More is not better. Under the described conditions, we are talking about half a can or so. This assumes the unit is cooling but maybe not perfect and the accumulator is not ice cold.

 

Ken

[pm26]

There is also a possibility of the orifice tube being partially clogged.(I assume this system has one). Partial clogging of the orifice tube of the expansion valve (if the system is so equipped) will cause inefficient cooling even if the system is properly charged. Perhaps the system needs to be fully evacuated and orifice tube inspected and cleaned/replaced, the system properly evacuated and charged.

 

I had a partially clogged orifice tube on my Mazda and no matter what I did I could not get the system to work properly. After replacing the tube, it was working great.

[xzz0195]

There is also a possibility of the orifice tube being partially clogged.(I assume this system has one). Partial clogging of the orifice tube of the expansion valve (if the system is so equipped) will cause inefficient cooling even if the system is properly charged. Perhaps the system needs to be fully evacuated and orifice tube inspected and cleaned/replaced, the system properly evacuated and charged.

 

I had a partially clogged orifice tube on my Mazda and no matter what I did I could not get the system to work properly. After replacing the tube, it was working great.

 

I believe as Ken stated earlier and as you mention, that the Schrader pin, became clogged when I tested it the second time and found the pressure to be in the "Alert zone" around 55psi. When I saw this, I attempted to let some out to get it down to 45psi, I was unable to do it with the tools I had, but some did escape. I'm thinking that later (the next day) that all of it escaped because there was no cooling at all. As I mentioned when I tried to reinject coolant the second time, no coolant would flow into the unit. The back pressure caused it to leak out of the charging unit hose... I'm pretty sure this indicates the Schrader pin is "stuck"... I guess I'll need to work on that pin to see if it's the cause.

 

BTW after I had put in coolant, it was much more cool than ever before, and as mentioned when I did this the first time with engine on and AC on max, the reading was 45 PSI. I only saw the 55PSI the next day when rechecking to make sure it was still 45PSI... It stopped working after the second check, the next morning.

[ken1mod]

Mr Sierra,

 

Just be careful and wear some kind of glasses. I am not a safety freak, I never wear a bicycle helmet, one must have some pride, but the a/c can spray juice out and freeze your eyeball. Glasses are a good thing here.

 

Let us know how things work out, I still don't think you wrecked anything.

 

In charging a system, even with gauges hooked up which looks really cool when your wife walks out, you charge slowly until the accumulator gets cold to the touch. This means some liquid refrigerant is spilling over from the evaporator into the accumulator. A small amount of liquid in the accumulator indicates a perfect charge for the conditions. As mentioned earlier, fan on high, engine at a slightly fast idle, maybe 1 thousand rpm or so.

 

good luck,

ken

[xzz0195]

Mr Sierra,

 

Just be careful and wear some kind of glasses. I am not a safety freak, I never wear a bicycle helmet, one must have some pride, but the a/c can spray juice out and freeze your eyeball. Glasses are a good thing here.

 

Let us know how things work out, I still don't think you wrecked anything.

 

In charging a system, even with gauges hooked up which looks really cool when your wife walks out, you charge slowly until the accumulator gets cold to the touch. This means some liquid refrigerant is spilling over from the evaporator into the accumulator. A small amount of liquid in the accumulator indicates a perfect charge for the conditions. As mentioned earlier, fan on high, engine at a slightly fast idle, maybe 1 thousand rpm or so.

 

good luck,

ken

 

 

Solution found and Thanks Ken for your help...

 

Went down to Napa after thinking about all the replies to this question on this forum. The results of my tests indicated to me (thanks to your insight) that the problem had to be in the Schrader valve. I bought a kit from Napa for about $7.00 that contained two valves and the valve removal tool. I pulled the old one out, (didn't have to worry about back-pressure because there was none)... Put the new one in and then dumped in 2 cans of 134A+. I very closely monitored the system after dumping in one can, and could tell there was not enough coolant. I measured the pressure 4 or 5 different times to ensure I was not overfilling. Pressure was good after two cans at around 40psi.

 

Note I also discovered, that on initial start up of engine with pressure gauge attached to Air Conditioning Low side, (as was mentioned earlier), the compressor will cycle on and off about 5 to 10 times. As it cycles there's a huge variation in pressure from low of 20 to high of 80 psi. Then after this goes on for a while this cycling settles down and the pressure stays more or less constant when there's the proper amount of coolant.

 

I also discovered that if you are low or have lost all of your coolant, the compressor WILL NOT cycle. Apparently this is normal behavior. As soon as the coolant was put in, the compressor kicked off.

 

As far as the Schrader valves are concerned, they have a small plastic bushing on them. I believe it was this plastic part that was bad. It looked like it was dirty and was most likely non-pliable any longer. This explains why when this old one was in the unit, why attempts to add coolant were 100% unsuccessful, as the valve was literally stuck open...letting all the coolant out and dissallowing coolant to be put in...

 

Thanks all for your help!