Learn me AC recharging? (Grinding noise from compressor)

So I haven't done much work with AC in the past, topped up a couple cars, took the system out of the Miata, but that's about it.

My wife complained that the minivan (2007 Odyssey, 95k-ish miles) wasn't blowing cold air any more, said it had been progressively getting more and more anemic for a while, finally wouldn't get cold at all. I figured that sounded like a slow leak of refrigerant, so I picked up a couple cans from AutoZone and grabbed my Harbor Freight gauge set.

It swallowed about 1 2/3 (12oz) cans of refrigerant before the low-side gauge got up to the 18-20C range, the whole time the compressor was only coming on for an instant before cutting off again. When the second can was mostly empty it started making a loud grinding sound when turning the compressor on -- sounded like the noise you get from a torque-limiting drill when you're using it to drive screws. That didn't sound good and it did it 2 or 3 times, so that's where I stopped.

Any suggestions on what's going on? Google suggests anything from it signifying incipient compressor death to being normal and I should ignore it. I'm fairly sure I didn't overfill the system, although the underhood label says nominal system capacity is 25oz, so if it really took over 1 2/3 cans, it must have been mostly empty. It did seem to have some pressure in it when I hooked up the gauge though.

That sound means it likely lost the compressor shaft bearing and seal thus when the 134 left the compressor took the oil with it. I bet if you wait a day there will be no 134 left.

Time for a real leak check and likely a dryer and compressor followed by a vacuum and N2 back fill and a vacuum before recharge.

Compressor is likely toast. Hopefully it didn't puke it's guts into the system. Replace the receiver/drier any time the system is open (like when replacing a compressor.) I've done it without the N2 backfill, just drawing a deep vacuum for an hour or so, then kill the pump and make sure it holds the vacuum overnight.

If you do replace the compressor, it will need the specified oil charge as well as the refrigerant.

The only time the compressor makes nasty noises is when it's failing. There's no nasty noise it can make that's considered 'normal'. Occasionally you have a worn clutch that slips and makes a nasty noise but it's not like what you're describing.

It sounds like your ac system needs an actual repair at this point. If you NEED it to work and don't want it to eat your time for the duration of however long it takes to learn all the possible pitfalls, i would just replace the compressor, drier, TXV, all o-rings, and flush everything before reassembly. If that sounds like too much work, pay someone else to do it.

Compressor is toast. It's a common failure on that gen Ody. Mine went at about 90k, replacement worked til about 230k

I agree with the bad news of a dead compressor. Get an estimate for a compressor and receiver drier. May not need to be flushed unless metal particles are found flowing through the system. Recommend at least having a shop do the recharging if you DIY the parts yourself. Like mentioned, the system needs to be pulled down to a vacuum for a long period of time to clear out any moisture that gets in the system during repair.

Yeah, I figured it was bad news for the compressor. I don't have a vacuum pump and my wife wants the AC to work soon, so it's probably going to a shop. Thanks!

If it humid when you open the system it really should get the N2 purge to dry up the moisture water can freeze in place under a vacuum. Small car systems usually not a problem but its a way to tell a good shop from a great shop as I'm sure you'll only want to do it once.