My A/C runs for 20 minutes, then quits blowing in the interior. Popped the hood and the low side lines and accumulator are frosted up / frozen. I let it thaw and ran it, it's good at idle, but give it some throttle and it starts frosting up. I let it run 15 min, noticed the clutch never cycles. Any ideas? I don't have much experience on air cond.

 

Get the pressures checked. Sounds like it’s low on refrigerant.

 

i was thinking the other way...over charged...flooding the evaporator causing the change of state to occur in the accumulator. Was it just filled and what method was used to charge it? If the high and low side pressures are high...have the system recovered and filled.

low charge would cause short cycling.

 

It will sit there idling and gets cold, nothing freezing up working great. Give it some throttle and it all goes downhill rather quickly. Anyone know if this is a cycling system or not? You'd think after driving this truck all these years I'd know this, but never noticed. But that there is no cycling kinda of makes me wonder if I have a switch issue.

I'll work on getting some gauges on it.

 

post the model year, engine size and i'll check the build

 

I'm out of town, but did get some gauges on it before I left. Static charge - 70 psi. at idle - 35/155. raise rpm's and low side drops accordingly, I saw 17 - 20 psi low side, and suction line immediately started frosting. I don't remember what the high side did.

This system has not been touched in my 10 years of ownership. The fact that it cools the cab nicely at idle, suction line sweating and all tells me it's not low. Tried searching this out online, no help. I'll take it to a shop when I get back in town if I don't figure something out.

 

So I went ahead and bought a kit containing new compressor, accumulator, and liquid line w/built in orifice. The compressor says filled with oil.

I will be flushing the condenser and evaporator. Will I need to add oil? If so how much and where do I add it?

 

yes, the condenser, accumulator and evaporator all will have oil residing in them. oil will need to be added to the system for proper oil balancing. Can't help you without know model year and engine.



are there any specific instructions for oil balancing the compressor that came with the compressor?

 

It's a 2005 4.7L, I've got to research it. the instructions tell you how to add oil to the compressor, but the compressor has a sticker saying prefilled with oil

The little bit I looked online is that prefilled compressors have oil to compensate for a clean system.

It may be safer to drain this thing and refill with the correct amount just to be safe. once i figure out how to do that. I'm not tackling this job for a couple weeks, so just trying to get a game plan together.

 

The factory compressors i have changed have tags on them will instructions that differ from the factory information. They instruct you to drain the old compressor and remove that amount from the new compressor. If nothing comes out of the old compressor....you take nothing out of the new compressor.

here is some confusing factory service info.
total system fill is 6oz
3 residues in the accumulator
2 in the evap
1 in the condensor
compressor.....drain the old and new compressor and add the volume that came out of the old compressor...add the equal amount to the new compressor.