Air Conditioning Over Charged?

[Craig]

So after many hiccups, I finally got my 1994 Yukon's A/C working. The shop charged the system and it seemed to be working fine, I just took it on short trips.

Unfortunately, it's looking like it's still not working properly. After about 10-15 minutes of driving with the air conditioning on, the clutch starts kicking in and out every 10-20 seconds. As well, there's a huge amount of condensation coming from the bottom of the heater core.

The high pressure switch went just a few weeks ago and they had to top up the system. Does it sound like they over charged it?

 

[Knuckle Dragger]

No, it sounds either under charged or the orifice has an issue allowing the evap to freeze.

 

[Craig]

Could be a tad undercharged as well. Just seems to be blowing very cold for it to be.

Orifice tube was replaced along with compressor two years ago.

 

[Knuckle Dragger]

Could be a tad undercharged as well. Just seems to be blowing very cold for it to be.

Orifice tube was replaced along with compressor two years ago.

Parts break or have issues as time goes on. Thank God because it keeps me employed. If the compressor is cycling that fast something is wrong and it isn't a "tad" wrong it's "get on it before you damage something" wrong. It sounds like the low side switch is cycling the compressor because the evap is freezing up. Honestly we can sit and guess on the internet all day. Without pressures and such that's all it is a guess. The shop that charged it should check it as a good will gesture. Anyplace I've ever worked would.

 

[98 Nitro]

Sounds like what I did when I accidentally overcharged mine which then lead to a leak.

 

[Craig]

Parts break or have issues as time goes on. Thank God because it keeps me employed. If the compressor is cycling that fast something is wrong and it isn't a "tad" wrong it's "get on it before you damage something" wrong. It sounds like the low side switch is cycling the compressor because the evap is freezing up. Honestly we can sit and guess on the internet all day. Without pressures and such that's all it is a guess. The shop that charged it should check it as a good will gesture. Anyplace I've ever worked would.

I'm quite sure now the excessive condensation on the evaporator was from the lines freezing.

I stopped into the shop today and they told me that they'd hook it up on Monday and check the pressures. They told me it was fine to use as is and there was no chance of the system being damaged as it was "self checking". Also they seemed to act as though the cycling was normal and mentioned that "these old trucks cycle 3 times as often as the new ones". It's kicking in and out every 10 seconds.

A little over a week ago they had to top up the system after the two week old high pressure switch they put in blew and sprayed oil everywhere so I think it has to be an overcharge.

 

[jdla140]

If the clutch is cycling every 10 seconds but theres still condensation and the air is still cold a few things could be happening. Most likely, an undercharge. Also possible: there isn't enough "load" on the system due to low ambient temps, a dirty evaporator, plugged intake, weak blower that is allowing low side pressures to get too low. this is usually evidenced by the lines being cold on more than just the low side of the system, for example if the suction tube to the compressor is very very cold this could be what is happening. It should be a little cold, but not freezing.

My money is on a low charge though.

 

[tom joyce]

The only way to accurately determine the amount of 134 in the system is to extract it and weight it. Any 'good' ac shop can do this for you for a reasonable price.
There is a chance that the 134 has to be (kinda) broken in. Start the system and let it run for a minute. Then 'gently' spray water over the condenser to cool it quickly for another 5 minutes. Then shut it down for an hour. It is a long shot, but may work...
My bet is that the system was charged wrong - not over charged. A vacuum was probably not held on the system long enough - causing water to possibly still be in the system. And the system was probably totally liquid charged on the low side.
Here is a pretty good article on properly charging an empty system. Notice the liquid charge on the high side - with engine off - and then the continued vapor charge on low side with engine on. This is the way I always do it, and I have never had a problem.
Hope this helps
http://www.aircondition.com/tech/questions/95/Basic-Charging-Procedures

 

[Craig]

Thank you for all of the suggestions and expertise guys.

I took it back to the shop. They checked the pressures, evacuated the system and weighed the R134A. They couldn't find anything wrong with it.

After attempting to recharge the system, it was deemed that the issue was with the compressor. They're covering a new one under warranty. Going with a new oem compressor this time. Last two were remanufactured ones and this is the third compressor put in over the last three years. My current 4seasons compressor lasted less than a month.

Still surprised, I thought for sure it was a charge issue. At least this is giving me an opportunity to put in something new rather than remanned.

 

[tom joyce]

Make sure the accumulator is changed too. When ever the system is opened up, the desiccant quickly becomes saturated with atmospheric water (condensation). The shop sounds to be pretty good, but they may say the accumulator is ok. BUT they are cheap enough to just replace for good insurance....
Any condensation in the system will cause the oil (lube) to become acidic - which destroys compressors (they call it "black death") in the auto-ac-world...lol. This may have happened to yours; and if the system has water/condensation in it, a new compressor will last a month too..
Truth be told - ac compressors will live forever as long as water/condensation is kept out of the system - and they are pretty easy to rebuild. 4 seasons compressors are pretty good for rebuilds.
Also, Pulling a vacuum does not remove the condensation/water from the accumulators desiccant. Again, accumulators are cheap enough to replace EVERY time the system is opened up - no matter for what or how long....
Sounds like you are on the way to a COOL summer!!