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.

 

A long delayed update. For the last year or so other things have taken priority so I haven't had time to do this job, but I've been gradually collecting the parts and tools necessary to do the job, and over the last two weekends I did it.

Before I started I checked pressure - the system was completely empty. I pulled vacuum and it held for about half an hour and then decayed. Disconnected the 12V battery and the service plug grip.

The first challenge was to remove the condenser. In Toyota's infinite wisdom they put aluminium condenser and radiator on top of steel brackets attached with steel screws. 18 years of salty winter roads later, what I have is a giant lump of rust. The screws have become one with the brackets, the heads strip instantly, and the fixing brackets at the bottom of the radiator assembly prevent removal of the condenser without moving the screw. About a day of drilling, bending, snapping... ensued. Eventually I had to bend the prongs on the steel lower brackets downwards and tear up the condenser in order to get it out. The aluminium fins at this point were mostly powder so this was no loss. I bought some new OEM brackets to replace these, but the current bracket is so rusted to the radiator it isn't going anywhere. The radiator looked in OK condition - I tried to drain it down to remove the rad pack but almost no coolant came out, so I decided the brackets and radiator were staying put. The steel is actually sound under all the rust.

Next I removed the compressor. A bit awkward with the car on short wheel ramps but no major problems. I could then pull out the high side pipe from the compressor to the radiator.

It took me a while to work out the clips for the HV cable loom - I couldn't work out how to open them. Turns out there's a lever on them but it doesn't open them. If you push that it'll disengage from the metal bracket the clip is attached to, and you can then pull the cable out without having to de-clip it. There's a bracket just above the compressor that's accessible only from the underside, and it would have been really handy to know how to remove the clip rather than unscrew the bracket from the engine block. Ah well.

I undid the clips holding the high and low side lines into the evaporator on the firewall: the official tool has two pins which both act on a U shaped bit of metal inside the clip. I managed to get this with a pair of picks. I pulled out the small high side pipe, but the larger low side pipe wouldn't budge. I decided against flushing the low side since any compressor/condenser debris is likely to be on the high side.

I flushed the high side from the firewall forwards, and the loose high side hose, with a Chinese AC flush cylinder and an air compressor, which worked ok. Might have been some dust in the fluid but hard to tell. I put about 2.5L of fluid through (bought 5L so why not use it?). Blew out the pipes with compressed air and left it to dry for a couple of hours.

Meanwhile I moved on to the AC compressors. The 'new' compressor was from a 2007 with 110K miles on the clock, which is fairly young for those being scrapped nowadays. I made sure to get one from a dismantler (Charles Trent) that properly plug the ports, as others sellers can just leave the compressors on the shelf for months open to the air. In my case I bought the compressor about a year ago but it was stored with plugs in.

I drained the oil from the old compressor (15ml) and new compressor (7.5ml). The next question was how much oil to add? I bought some Elke POE80 oil, marked ND11 and suitable for hybrids by the supplier (genuine ND-OIL11 is almost impossible to find in the UK and about something like £200 for 250ml). The calculation in the service manual is deeply unhelpful. Following the service manual I put 40ml in the condenser, and I decided to put 40ml in the compressor. I figured that if the system was completely dry there's be 80ml in it, which is slightly below spec but still workable. In the old system we might have accounted for 55ml of the old oil, so supposing there was 45ml in the evaporator then 45+40+40 = 125ml, again slightly out of spec but not egregiously high. So 40ml went into the compressor (low side port, it wouldn't take any in the high side port).

I changed all the O-rings. Supplier sent a set of green Chinese ones which I didn't like the look of, so I got them from Toyota (about £3 each, sigh). A pair of picks were handy to stretch them and avoid dropping them as I didn't have spares. I smeared them with a little POE oil.

• 90099-14119 (ID6.7x1.8mm): two on the firewall, one on the condenser.
• 90099-14120 (ID10.8x2.4mm): two on the pipe from condenser to compressor
• 90099-14121 (ID13.4x2.4mm): one on the low side pipe from evaporator firewall to compressor (there are another two on the firewall had I removed that)

Put the high side pipe back into the firewall and refitted the clamps to both sides.

Installed the new compressor underneath. This was a bit of a pain as it's heavy and awkward to position. Broke a screw torquing it up so had to remove and refit (not sure I trust the 18 year old screws to be strong enough, so I've not entirely obeyed the torque settings of things, aside from doing them up with an electric ratchet). Installed the pipes into the compressor, and fished them and the HV cable through to the top. Connected up the HV cable.

Next I installed the new condenser (which includes receiver dryer), having put in 40ml of oil. Having bent the support brackets every which way to get the old condenser and screws out, it was a job to bend them back into the correct shape and get new screws to fit. Finally did it and screwed in new condenser. Connected up hoses.

Hooked up my cheap Chinese manifold gauges and pulled vacuum. First time around I pulled vacuum for about half an hour, then I was poking about elsewhere in the engine bay, there was a click and more vapour started coming out the vacuum pump - seems like the bayonet connector wasn't activating correctly and the high side hadn't opened. Pulled vacuum for about another half hour. Closed off the valves, removed the pump and left it for an hour - still good vacuum. So far so good.

Next up was to introduce some refrigerant. In the UK there's exactly one brand of R134a available to consumers - it's called 'AC Pro' and is about £60 for 510g once you get the cylinder deposit back. What I hadn't realised is there's only 425g of refrigerant and 85g of 'stuff' - dye, leak stop and so on. It says it's good for hybrids and EVs... I don't have any other option, so let's give it a go. The cylinder has a recloseable Schrader style valve on it, and the manifold gauges came with a screw tap intended to puncture a can, but can also push down on the Schrader pin. Everything screwed together ok. The full 425g is a bit lower than expected but just about in spec, so the whole can needs to go in.

Opened up high side and low side and let some gas in - got up to about 95psi on both sides. I turned the car on and could hear the compressor spin up, so there was obviously gas in it, but the cylinder was nowhere near empty. Whatever I did I couldn't it to shift from 95psi - and on both sides means the compressor isn't working. Quite a puzzler. What made it worse was the tap on the refrigerant cylinder appeared to be jammed open, so I couldn't release the cylinder without leaking refrigerant. (later analysis indicated the pin on the tap had bent, jamming the cylinder valve open)

Put the car into max cold, high fan, windows open. Closed up the high side - I realised that having both sides open was a short circuit across the compressor through the manifold, so no surprises there was no pressure differential high to low. Still couldn't get it to budge from 95psi each side, still warm air coming out the vents. Had a play with Techstream trying to spin up and down the compressor, no dice.

Then a bit of wiggling told me that the valve on the low side of the manifold gauges wasn't reliable - with the knob in the open position, it was possible to set it at a slight angle which closed the valve - then we were just seeing trapped pressure and not from the system. With the valve properly open, the low side pressure started to decrease. At this point I could invert the cylinder and gradually feed in refrigerant in batches, watching as the low side pressure came down and then rose when I fed in more.

Once the cylinder was empty, time to test. Max cold, windows closed...

AND. IT. WORKS.

It was the hottest day of the year so far - 32C. At the time I tested it was 28C, and the air coming out the vents got down to 6.9C. That's actually colder than the refrigerator I stole the thermometer from.

We'll see whether it holds up long term, but it's looking good... and now that the compressor is fixed I can take it to regular AC shops for regassing if needed.

So my take home message is don't buy cheap Chinese manifold gauges or taps, they're rubbish and make the job harder (and higher risk, had the cylinder valve actually failed).

Would I do it again? Depends. In 2019 I got a quote for £1000 for Toyota to replace the compressor, but I see just the part alone now is £1400 according to the local dealer. I definitely saved over that. A not-very-local independent quoted about £530, but I don't remember what's included with that - just the compressor, no condenser? Maybe that was just labour cost, parts extra (would they source a used compressor? It certainly wouldn't have been a new one). Given the state of rust it may well have been a bigger job than even that quote included, although that would have been on them.

I haven't added up the outlay on parts, tools and consumables, but at least I now have various tools some of which will come in handy in future (I didn't actually want to buy a shop air compressor but can think of several uses for it now). So what I saved on labour I get back in additions to my tool collection.

Anyway, that was a bit longer than expected but hopefully covers a few things that are mentioned piecemeal in other threads, for anyone who has to do this in future.