KahnBB6

iTrader: (5)

Sure thing

RXRodger

iTrader: (2)

I don't have a book so that is my term, not sure what Lexus/Toyota actually calls the part. It is the large swell in the line right under the ABS unit. I have never seen one of these on an a/c system before so I am just not familiar with it. There is a sensing line coming from the expansion valve that looks to control it, but I really haven't studied it much to see exactly what it does. This is only an assumption, but I assume it controls downstream or lowside pressure very exactly to get the most out of the system. It looks just like a pressure regulator to me. This is merely a guess, maybe somebody will come on here an explain it.

Anyway, I did this job you are doing this summer. Replaced the drier, expansion valve, oring kit on the compressor, etc. When I recharged it with 134, the head pressure ran really high, and the cooling was minimal so I think maybe there was an issue with this "regulator". Then I blew the discharge line out of the compressor, which turns out the be a very expensive replacement. So, I said screw it and stripped the car out and made a track car out of it. Unbelievable track car, but I digress.

Long story short, hopefully you won't run into the same issue, but just something to think about as you go about this job.

KahnBB6

iTrader: (5)

^^ Thanks, RX Rodger! I actually got this taken care of in early September of this year.

For those who may be searching re you sure you aren't referring to the thermal expansion valve? (TX-Valve?)

For me the main problem area was a leaking original evaporator core and a bad TX-Valve which was causing the high pressure problem I was having.

I had a new Denso OEM evaporator core and an OEM Toyota TX-Valve installed (refer to post #8 on page one for the Denso OEM version). Because the system would be apart and due to the age of some of the A/C components I went ahead and put in a new Denso OEM condenser, Denso Drier and had one of the front lines coming from the Drier cleaned of pellet contamination. I'll note that I just had my mechanic do all of this other than tearing down the dash for him prior to dropping the car off. I'm not an A/C guy.

A bit overkill but I wanted to make sure the system had a clean slate.

Also, I'd replaced my A/C compressor a couple of years prior and I put in a set of new high and low pressure lines at that time. The reman compressor wasn't bad but those lines weren't cheap even bought well below MSRP.

TXMAG

iTrader: (1)

Do you happen to have part numbers for those lines? Also, I assume that upgrading to the R134a components was just a matter of using a later model SC300 components?

KahnBB6

iTrader: (5)

Here you go. I had to dig these out of my records. So many part numbers I haven't copied into electronic files yet.

Lexus SC300 A/C Compressor lines OEM Lexus:

88712-24140 Hose, Suction
88711-24100 Hose, Discharge

Regarding how to convert an R12 SC to R134a, your guess is as good as mine. Yes, I'd assume you would just need to replace anything that was strictly R12-only with anything that supercedes to R134a-only. There may be some valve fittings for the hard service lines that get changed too along with O-rings... components you don't normally think of replacing with A/C services. The system would have to be purged of all old R12 lubricating oil before filling with R134a lubricating oil since that would harm the system while running R134a. But to the best of my knowledge you're right.

The cars were designed for both standards so it should not be that difficult. Just a bit pricey to do all at once.

TXMAG

iTrader: (1)

Yikes! Those are some expensive hoses. Probably looking at close to $1000 to completely retrofit the old R12 system to R134a using all new OEM/Denso parts and that's if you do it yourself. Guess I'll test my existing system first when I get back to the US and go from there.

Thanks again for the info Kahn.

KahnBB6

iTrader: (5)

No problem. If you're doing all of it you'll be spending quite a bit. For all the Denso stuff:

Denso SC300 Drier -- P/N #478-0107 -- Rockauto/Denso $13
Denso SC Cabin Air filter -- P/N #453-1003 -- Rockauto/Denso $25
Denso SC Evaporator Core -- P/N #476-0055 -- Rockauto/Denso $168
Denso SC Thermal Expansion Valve -- P/N #DEN475-0106 -- Rockauto/Denso $50
Denso SC Condenser -- P/N #477-0115 -- Rockauto/Denso $228

Reman R143a A/C compressor... really anywhere you trust that does a good reman. I used Driftmotion for mine.

For the Lexus specific parts (After all the Denso stuff just the pressure lines??) try Carson Toyota, Pembroke Pines Lexus, or Lexus South Atlanta. There's also Amayama but international shipping will be more with large parts. Plus the waiting time.

However you do it it's going to be a big bill. But once it's done you'll have a brand new system. Good luck, TXMAG.

RXRodger

iTrader: (2)

There is no reason to replace the lines unless they are bad. Typically just change the drier and get a good flush.

pishta

My 92 was R12, converted it to R134 with only the fittings being changed out (no O-rings, PAG or drier). My Dad was a broke-*** saint that saved a bunch of money and finally bought this car 2nd hand and loved it until he succumbed, Before that though, he wanted it converted to R134 as the R12 leaked out a bad low side valve (bubbles!) and R12 was $20 a can by then. So we bought R134 fittings and a few cans of 134 with a fill adapter and filled it up to the cheapo valve on the adapter, worked! Fast forward 10 years. My son drives the car now and the A/C hasn't worked in years, still leaked $15 a can (california) R134. I said F it, and pulled a vacuum, didnt notice a leakdown and pulled in 55psi worth of $4 Coleman camp propane out of an adapted torch head clamped to an old manifold line. the SOB started blowing COLD air again! I ran it like this for 3 years with a top off ever 3 months (My 2002 Silverado gets the same R290/propane treatment every 3 months and it blows at 43F) . I think its dead now. 120 psi on the low side whether its turned on or off. Have not looked at compressor clutch yet as hes away at college but he'll graduate soon so Ill have a chance to check it out again. I watched an RX300 change out and the entire dash had to come out. F that, Ill just straight pipe it and roll the windows down.