Long broken A/C compressor replacement

I bought a 2006 UK Prius in 2016. It was cheap because the air conditioning didn't work (not that the seller told me that...). This didn't bother me so I've been driving it ever since (now 170k miles).

Now I have reasons that I might want to fix the A/C. Last time I looked into this, in 2019, I took it to a dealer who said it was full of gas but the compressor was dead - that's also what Techstream told me. £1000 fee to fix it - perhaps not.

The guy who sold it to me had taken it to various 'fast fit' places for repairs, and my suspicion is he took it somewhere for a regas and they didn't use the proper oil. But I don't have any evidence for that.

So, supposing I want to fix this, what should I do? I'm thinking:

1. Take it somewhere to remove all the gas from the system, who support hybrids
2. Flush it. Does a regular A/C flushing service work for this, or does it need something extra to get rid of potential spurious oil? Does it matter if it's had the wrong oil for an extended period?
   
3. Install a fresh compressor. We don't have refurbished or aftermarket ones available in the UK, so it's either one from a scrap car or a 'new' one from China ('Happy Touring' brand ES18C on Aliexpress). The latter doesn't sound enticing. What should I be looking for in a scrap one? Is it meaningful to test electrical resistance to check the coils are still intact? Any other checks?
   
4. Should I ask them to plug it to keep the oil inside? Or drain it and add fresh ND-11? What happens if there's too much oil? What if I buy a compressor and don't fit it for a while, do they go 'stale' if exposed to air? (eg if the compressor was removed from a donor vehicle and has been sitting on the breakers' shelf for a while)
   
5. Once it's fitted, anything different from a standard vacuum and regas? Do a second flush?

I would likely need to find somewhere to do #1, #2 and #5. Of the limited number of places locally who support hybrids they don't seem to like doing something that's different to their usual routine, so it's useful if it's 'just a regular A/C service'.

Are there any other pitfalls in trying to fix a car with dead A/C for this long?

 

That's interesting - the link in the above thread works on the Wayback Machine with date 20190414210550 (can't post the direct link).

So I don't actually know a great deal about A/C servicing, but I was assuming that when A/C shops offer a 'regas and clean' service, that would involve flushing the refrigerant system. But maybe I'm wrong here. In particular I doubt they're going to have any specific machine (for one thing, likely not a US machine), just whatever they use on other hybrid vehicles. When changing the refrigerant (eg if it's leaked or got moisture in it) do they do a flush?

Absent one of those machines, am I looking at a full system replacement - which is what: pipes, evaporator, condenser?

Good point about the drier, that's worth doing.

 

Hmm, digging around what various chains mean by a 'clean' service, it seems like they're talking about antibacterial treatment, which sounds like they're spraying something on the cabin side of the evaporator - ie nothing to do with the refrigerant. So they aren't actually doing any kind of flush.

Anyway, I scanned it with Techstream again and I'm just getting:
B1423: Open in Pressure Sensor Circuit / Abnormal Refrigerant Pressure

but the A/C tab doesn't show pressure switch status - ie if it's high or low pressure (seems like there isn't a separate signal for that, so it doesn't know, but there's not even a line for the switch).

I pulled up a saved scan from 2019, which is about the time I took it in to the dealer, and I have:
B1421 SOLAR SENSOR CIRCUIT (PASSENGER SIDE) (I think this one doesn't matter)
B1472 A/C INVERTER HIGH VOLTAGE OUTPUT SYSTEM MALFUNCTION
B1474 A/C INVERTER

The last two are 'historic', but that might have been because I cleared codes for something else.

If I run the A/C on max cold, the compressor stays at 0 rpm. If I use the tool in Techstream where I set the compressor speed in rpm, eg 800 or 1000, it stays at 0 rpm. I think previously after I've cleared codes, if I turned on a/c it sounded like trying to spin up and then threw B147x.

So maybe there's now no gas in it, but that is masking the compressor problem? In which case, what procedure should I follow to make the system usable again?

 

(For the record, my posts are being moderated as a new user, so they're showing up a day late. Once they get approved they appear in the middle of the thread)

Anyway, I went through the procedure for checking B1472, being to unplug the compressor and check resistance. That was much less trouble that I expected. It actually looks all good - 0.5-0.6 ohms on each coil.

So does that point the blame to the inverter?

 

Also, I've been digging around my old Techstream save files. I found one about 6 weeks after I bought the car, and that has (last 3 historic):

B1421 solar sensor
B1472 A/C Inverter High Voltage Output System
B1474 A/C Inverter
B1476 A/C Inverter Load System

So I'll take a todo when I have some daylight to do the B1476 test procedure (condenser fan and refrigerant check).

 

Done some more investigation. The condenser fan runs fine. B1423 returns even if I clear DTCs. The A/C pressure switch is open circuit (no continuity between any terminals), and when I run it there's nothing changing inside the sight glass (even if I tap it etc). So I suspect it's empty of gas, which is inhibiting any further investigation.

One thing I could do is jumper out the pressure switch and very slowly spin up the compressor using Techstream (to whatever the lowest speed is, 100 rpm or something?) to see if it'll spin. How much of a terrible idea is this? Am I likely to burn out a good compressor even at that speed? Really I want to confirm whether the inverter is behaving itself.

Otherwise I suppose I have two options:

1. Gas it up, see if the compressor works, if it doesn't drain it, clean, change the compressor and regas it
2. Remove the compressor, replace with a used one and regas. If I take apart the old one and find debris, either trying to clean the system or just taking a risk (used compressors are cheaper than replacing/flushing much of the system, although doing the condenser/receiver-dryer might make sense)

It seems like I can't buy R134a without a licence (only the 'substitute' highly flammable propane/isobutane mixes) so I'm wondering whether to do #2 - swap compressors and then take it somewhere for regassing, given #1 would require 3 visits to the A/C shop anyway. (I have tried to ask some about replacing compressors, but they don't answer - I suspect they don't want to get into that kind of job for hybrids).

 

It appears there's exactly one brand of R134a available to the non-licensed market, and that's £70 per pound and not recommended for hybrids. It would be cheaper for a pro to do it compared with that. There's also some slightly dubious brands of propane/isobutane mix 'R134a replacement', which could effectively be relabelled camping gas...

Anyway, I tried jumpering out the pressure switch and asking Techstream to run the compressor at 100rpm for a couple of seconds. It sounds like it's spinning up - it's loud, but I guess that's to be expected if the system has no gas in it.

So my current question is: how to distinguish if there's an inverter or compressor fault? If it is making spinning noises, does that mean the inverter is OK? Or could a faulty inverter still spin it up but throw DTCs later?

If there is a refrigerant side fault of the compressor (eg a shredded scroll) then presumably the inverter can't sense that, it can only sense that the compressor runs at an abnormal speed?

Following the service flowcharts:
B1472 says to check the compressor coil resistance (looks good 0.5ohm), if good replace inverter
B1474 doesn't have a service page, but the contents page says an inverter malfunction (on the Gen3 it's replace compressor, but that has the inverter integrated).
B1476 says check condenser fan (looks good), if good check refrigerant (low), if low refill, if level good replace compressor

On this basis we have two votes for inverter and one vote for compressor. Does this make any sense? Should I try replacing the inverter first?

Should I gas it up with the camping gas for the purpose of testing, or is that like to cause trouble? (is that stuff a bad idea for hybrids?) I can't pull vacuum, but could try to at least put some gas in it? I could just vent the propane later if needed.

 

Maybe, although the PDFs floating around don't look like prints to file, and the DTC listing links to service pages on every other DTC but has no link for B1474. However I also found a copy of the HTML GSIC for the 2008 (which I think is what you get if you subscribe?) and that doesn't admit to the existence of B1474 at all. I'm wondering whether there was an ECU change in some markets that generates this additional code - perhaps that only landed for everyone for the Gen3? I've seen 2009/2011/2012 and Lexus RX400h/GS450h have it. But of course on all of those the compressor and inverter are the same unit, so the advice is to replace it - not much clarity for me.