2014 Silverado 1500 AC Trouble

[jellis56]

Need Help with AC Problem Edit | Quote | Reply
2014 Silverado 1500 w/5.3L Ecotec engine.
Replaced the following:
Compressor
Condensor
Expansion Valve
Low side line w/two mufflers
High Pressure Switch

AC is cooling great, but having two issues:
1. whirring sound when ac is on-

When AC is running and I accelerate, I'm hearing a whirring or whining sound. It sounds like it is coming from the passenger side around where the evaporator is.

2. low side line frosting up where line comes out of expansion valve-

I have vacuumed and verified there was no leak when setting this up.

One of the things I have noticed is after the initial charge (around 25) the compressor clutch is engaged and I have not noticed the compressor cycle off and on again.

I'm learning that as a DIY, this AC fix is becoming more complicated then what I had anticipated.

I could really use some help, pointers, tips, etc.

[JohnHere]

I'm learning that as a DIY, this AC fix is becoming more complicated then what I had anticipated.

Yes, indeed...as you're discovering, it's not only complicated but also very tricky and time consuming to diagnose and repair, especially if you don't have sufficient knowledge about vehicle air conditioning systems and the proper equipment. Sometimes, it's just best to leave it to a pro.

With that, I have a few comments and questions:

The sound that you're hearing from the passenger side is most likely coming from the TXV. It could be the replacement TXV out of spec and acting strangely, or it could be a refrigerant-charge issue. Ditto for the line just past the TXV that's frosting up. If you still have the original TXV, hold onto it as you might have to reinstall it. I've found a number of aftermarket TXV's that didn't work right, requiring re-installation of the originals.

When verifying that there weren't any leaks, how did you do that? Note that just because the system holds a vacuum doesn't mean that it won't leak under pressure.

How did you charge the refrigerant? The spec I have calls for 24.7 ounces of R-134a, which must be metered in precisely by weight (not fluid ounces) using an accurate refrigerant scale.

How did you verify the oil charge? My reference specifies 7.1 ounces of PAG-46. Some new compressors come with a full oil charge and some don't. It's always good practice to drain and measure the oil in a new compressor, then refill it with the proper amount and grade of fresh oil. A new compressor with a deficient oil charge won't last very long in service.

One of the things I have noticed is after the initial charge (around 25) the compressor clutch is engaged and I have not noticed the compressor cycle off and on again.

The compressor not cycling could be normal or it could be because the refrigerant charge is "off." Modern vehicles need to have the charge "right on." With some vehicles, just an ounce or two either way can make a difference in system performance. Around 25 (ounces in weight??) plus an incorrect oil charge might not be close enough to the specs for your vehicle's A/C to continue running great over the long term.

[jellis56]

It held a vacuum for well over an hour. Vac pump off. I'm pretty sure there was no leak.

How I filled it with R134A:
With it under vacuum psi, engine off, I turned a 12oz can upside down and let it in the high side. until the gauge needles went above 0 and low side was up to 20psi or so.
then I turned engine on, clutch kicked in, and put the remainder of the can in low side. I tried using a kitchen scale in oz, weighing the hose together with the can, using the "Tare" weight setting. (Yeah, that's probably not the right way to do.) I bled the yellow hose at the valve on the manifold to purge out any air before letting in refrigerant

In total, I'm estimating I put in the one 12oz can and roughly 90% of a second 12oz can. Could I have put slightly too much in it, probably. Sticker under hood says it takes .62 Kg R134A.

When truck is sitting, start it up, drive down the road with AC on, within a minute the whirring noise which sounds like it is coming from the glovebox area starts up. Definately not a normal engine noise, it increases with acceleration. after driving it around the block I return home, pop the hood and less than a minute the whirring disappears. I've tried to probe around with a stethoscope but by the time the hood is open and I get the stethoscope on my ears and getting someone to press the gas pedal, the sound is gone.

Regarding the Pag 46 oil. I've got about 7oz of Pag oil in it. I put 3oz in the compressor and later found out the system uses 7.1oz and added the other 4 by vacuuming into the high side by opening the low side valve on the manifold and the high side hose stuck in a bottle where I put in a measured amount of Pag oil.

I still have the GM Expansion valve and the AC Delco Compressor that came out of it. I have a O'reilly's "Murray" brand new compressor installed. Comparing the Murray to the original AC Delco I noticed the AC Delco clutch spins much easier than the Murray. Makes me wonder if the GM compressor is worn out?

Backstory to why I did this AC work: bought the truck in Jan. it was 16 F outside, discovered a month ago the ac didn't work. no warranty for it. So i decided to tackle it myself. found the leaking condensor spot weld and bought a new one oneline, decided to change out the compressor, seeing it has 96k on it.

Thanks for taking your time to get some ideas to help fix this.

[jellis56]

Gauge readings I wrote down yesterday:
ambient temp 77
low" 45-50psi
high 155-200

AC temp in cab using a therm stuck in the middle vent was in the 40's