A/C recharge problem (1 Viewer)

[CharlieBronson]

Hi gents,
After getting a new a/c compressor/new desiccant pack in (no more crunchy squealing- yay), I hooked up a/c manifold/pump and pulled vacuum for an hour, then let it sit for an hour (no leaks).
Hooked up the first can to the high side (with engine off) and got a little in.
Then moved to the low side/engine on-1500ish rpm/a/c on full blast.
Things were going well on the first and second cans- pressures were looking good, dropping down into a normal range as the compressor activated and pulled refrigerant into the system.
When I got to the third can, pressures starting getting really high, especially on the high pressure side. Of course these pressures were fluctuating with the compressor that would not stop turning on and off every 5-10 seconds.
At that point I stopped.

 

[LJE]

Hi gents,
After getting a new a/c compressor/new desiccant pack in (no more crunchy squealing- yay), I hooked up a/c manifold/pump and pulled vacuum for an hour (no leaks).
Hooked up the first can to the high side (with engine off) and got a little in.
Then moved to the low side/engine on-1500ish rpm/a/c on full blast.
Things were going well on the first and second cans- pressures were looking good, dropping down into a normal range as the compressor activated and pulled refrigerant into the system.
When I got to the third can, pressures starting getting really high, especially on the high pressure side. Of course these pressures were fluctuating with the compressor that would not stop turning on and off every 5-10 seconds.
At that point I stopped.

I'm no AC expert (that would be @flintknapper I believe), however, why did you replace the compressor? If it's because the old one died, it's highly likely it threw very small shards of itself throughout your AC system, and one of those is now clogging you expansion valve (TXV) at your evaporator(s).

If that's the case, the system needs to have the R134a you put in recovered back out, then dissembled and each part flushed individually - replacing the TXV valve(s) (do you have just front, or front and rear AC?) as well.

 

[CharlieBronson]

I'm no AC expert (that would be @flintknapper I believe), however, why did you replace the compressor? If it's because the old one died, it's highly likely it threw very small shards of itself throughout your AC system, and one of those is now clogging you expansion valve (TXV) at your evaporator(s).

If that's the case, the system needs to have the R134a you put in recovered back out, then dissembled and each part flushed individually - replacing the TXV valve(s) (do you have just front, or front and rear AC?) as well.

old compressor still worked/blew cold- it was just getting really noisy. once I started it up with the new a/c compressor in, everything was back to sounding normal.

old A/C compressor : ac off initially, then I turn it on at :23

 

[CharlieBronson]

bump and note:

evacuated the system, started over.
got about 2 1/2 cans in but noticed the compressor is continually running, not cycling.
low side pressure good, high side pressure continues to build past 350 and I stop.

with the compressor running constantly/not cutting off = building pressure on the high side, what about a bad pressure switch?

 

[SteveH]

I have forgotten offhand what the system capacity is, but I assume 2.5 cans is not greater than the max?

A key metric in system charging is watching the center vent temps with a good probe (not infrared) thermometer. Are you doing this?

I wonder if you are overcharging the system. What is your center vent temp while you are charging the system? A rule of thumb is to quit adding refrigerant when you get a good center vent temp (fan set on high, windows open, set to 'fresh'). If you are seeing 40-45F at the center vent, then stop. Never mind the stated system capacity.

Your low side pressures should vary with compressor cycling (though not at much as the high side). If your expansion valve is clogged, you may see too-high pressures on the high side, because the compressed refrigerant has nowhere to go.

 

[CharlieBronson]

I have forgotten offhand what the system capacity is, but I assume 2.5 cans is not greater than the max?

A key metric in system charging is watching the center vent temps with a good probe (not infrared) thermometer. Are you doing this?

I wonder if you are overcharging the system. What is your center vent temp while you are charging the system? A rule of thumb is to quit adding refrigerant when you get a good center vent temp (fan set on high, windows open, set to 'fresh'). If you are seeing 40-45F at the center vent, then stop. Never mind the stated system capacity.

Your low side pressures should vary with compressor cycling (though not at much as the high side). If your expansion valve is clogged, you may see too-high pressures on the high side, because the compressed refrigerant has nowhere to go.

I didn’t watch temps at center vent.

2 1/2 is like 30oz, I think the system holds 39.

but compressor is not cycling off, clutch is engaged the whole time

 

[SteveH]

I'm fighting a '00 4Runner with the same thing - after adding 1 can, the compressor runs continuously, but A/C is lukewarm and high side won't go over 180 psi. I suspect either a worn out compressor or a plugged expansion valve, or both. It's my daughter's car and the A/C works well enough, but it needs long-term love to fix this.

 

[GremlinMobile]

My old cruiser had that loud rattle from the AC compressor for years.. Never did quit on me. Just always rattled like a bastard. Now my GX has that rattle too. What causes it? Apparently the rattle doesn't indicate it's about to fail since mine lasted forever with it.

 

[dbleon]

I thought you were only supposed to add fridge through the low side?

 

[CharlieBronson]

just ran a hose on the condenser with everything hooked up.
the high pressure reading went down down down into normal.
zeroing in.

and although this is a '98, it appears I'm missing something here in front of the gnarly ass condenser...

so if anybody wants to weigh in- I'm guessing new condenser & add fan back in?

 

[CharlieBronson]

I thought you were only supposed to add fridge through the low side?

with the engine off you can add a little in on the high side first

 

[Moparsncruisers]

How are you measuring the amount you put in? It's kinda important so you don't overcharge the system! When doing it old school with cans and manifold charge on the low side, once the compressor clutch engages it'll suck the refrigerant in. What's your low side pressure? 350 on the high side is too high for sure! That's either a blockage (condenser, drier) or too much refrigerant.

 

[CharlieBronson]

How are you measuring the amount you put in? It's kinda important so you don't overcharge the system! When doing it old school with cans and manifold charge on the low side, once the compressor clutch engages it'll suck the refrigerant in. What's your low side pressure? 350 on the high side is too high for sure! That's either a blockage (condenser, drier) or too much refrigerant.

I've got the cans on a little food scale measuring oz's.
the low side is sitting between 25-30.