Compressor change in a Gen II

So, I purchased a 2005 Gen 2 Prius, UK spec, around 18 months ago with broken air con. Following the recent mini-heatwave, the time finally arrived this weekend, to fix the problem!

Symptoms... 50psi on both the HP & LP sides of the air con, with the compressor running. Some crunching noises (now stopped) and a rather unpleasant whine coming from the compressor.

Having perused PriusChat and taken some advice, (thanks John / Britprius) I purchased a vacuum pump, manifold gauge, pipe freezing kit, second hand compressor, air drier and ND-11 oil - thanks e-Bay.

Removing the compressor and replacing was straightforward enough - when the old compressor came off & was opened up the damage was very obvious - a lot of swarf & pieces of broken scroll - see pictures. I couldn't get more than a few ml of old oil out of the compressor, so as I was replacing with a used compressor from eBay, decided it was best not to add any additional oil as the right amount should be present in the replacement used compressor. For access, I took the whole of the plastic under tray off, it only takes 20 minutes & it makes the job easier.

Unfortunately I couldn't get the air drier on the condenser open - it was rusted well shut & I didn't really want to move on to replacing the condenser if I broke it, which would have involved splitting the condenser from the radiator, on fittings which were also well corroded. As the system had remained gassed up & was de-gassed & pulled hard down to a vacuum and then allowed to warm up before it was opened, I hope the old air drier will have enough life in it for the new charge... I did vac the system down for 45 mins to pull as much moisture out of the old drier as possible before letting the system sit to prove the vacuum.

To get the condenser into a workable position, the bodywork on top of the condenser / radiator was taken off and the assembly was pulled forwards to allow access from below.

On charging R134a from an artic polar pipe freezing kit was used... (oil free). John's method of drilling a hole in the LP dust cap & injecting there worked for me, a little bit of electrical tape around the inside edge of the pipe worked as a gasket. There was some leakage & although I weighed the R134a added, I used the HP & LP operating pressures to judge when the system had sufficient charge as it was impossible to judge how much was leaking & how much was going in.

All in, I brought the system up to 50psi before running the compressor, this was enough to allow the compressor to run by re-setting the low charge cut out. I then added sufficient gas with the compressor running to bring the HP side up to 200psi operating.

All in 855g of R134a were used, well over the 450g spec but quite a lot attributed to leakage owing to the filling method. Once filling was completed, the LP filling point was re-connected to the manifold gauge.

The system operated at a max pressure difference of 30psi on the LP and 240psi of the HP against a spec of 22 - 36 psi LP and 185 - 210 psi on the HP. The minimum HP pressure with the system running was 150psi.

The system was then allowed to relax & came down to 85psi HP & LP sides against an initial value of 50psi before I started work.

Overall I think the system is a little overcharged due to the inaccuracies of the filling method, but not excessively so. 240psi on the HP is a little high, but not completely outrageous & the system was blowing cold. So, my plan is to run the car like this, see how it performs & if the air con is a little ineffective, remove some of the gas to get the HP down to a mid range 200psi max.

I couldn't see any interesting effects in the sight glass.

Thanks for reading

Matt

 

Hi Patrick, I couldn't find any in the UK with no standard oil in it. John (Britprius) seems to have had this problem before, hence the pipe freezing kit & leaky filling method!

I don't know whether there is any debris in the the drier. My reckoning was that getting the drier open was going to break it & as it was a cheap eBay compressor, I'll take a chance that the swarf has stayed within the old compressor - or at least is properly trapped in the drier and won't move about.

 

Hmm, fortunately I haven't had to do any leak fixing - having run it for a week, the system has held pressure fine. I hope the dye works effectively for her.

Unfortunately my air con repair has not proved very effective, cooling performance in hot weather has been poor, so today it was time for a re think.

I hooked up my other Prius (air con undisturbed from new) to the manifold gauges & found that at an ambient temperature of 21C measured on the car, with the air con resting the pressures were HP 62psi, LP 70psi. With the air con running, the pressures became HP 160, LP30 & the ambient temperature measured held at 21. The vents blew icy cold air.

So, I then hooked up my repaired Prius, exhibiting poor cooling performance. At rest, the pressures were HP 80, LP84, ambient temperature 21.

From this I concluded that my repaired air con was over charged & reduced the standing pressures to HP 63, LP 70, ambient temperature 20. This took quite some time as removing refrigerant from the system causes a temperature change, so the system has to be allowed to warm back up, which increases the pressure, prior to settling down again.

I then ran my repaired Prius. Operating pressures were now HP 130, LP30, T20. Happily the vents now blew icy cold air.

Interestingly this one runs a little lower on the HP than the other, but the LP pressures are identical. Prior to the pressure reduction, the system also operated at LP 30, but with HP 240. I think from this we could speculate that the air con control system targets an LP pressure of 30 psi as a primary control loop with the HP side following? I don't know if anyone else who is more knowledgeably on air con control has any views on this?

Given the system now seems to be working much more effectively, I'm going to leave it like this & see how it performs.