Automotive Air Conditioning Information Forum

The Burb is a 90 with the 5.7 (only 80k miles, sat for the last 10 years). The ac system is empty and open. My dad was in the process of changing some seals but never finished. What would be the best method/parts I would need to get the best performance. I plan to just seal off the rear ac and buy new condenser, compressor, and accumulator, hose, ect.

Thank you

Someone here will know if this vehicle is able to be converted successfully to R134a.

Original R4 compressors worked OK, had marginal lifetimes when used with rear evaporator, so blocking off the rear should help. There are conversions to use more-modern compressors in this however.

My guess biggest issue is if the threads on the front evaporator are still OK when you remove the accumulator, not a great set-up. If those are bad/galled you may need a new front evaporator too.

The correct way to do it is replace compressor, condenser, orifice, flush evap, o-rings, presser sensors, with after market R-134 system parts all you keep from the old system is your evaporator you can get a quote from ACKITS.COM. I have done this it requires custom hose's but you can get those made not that much cost little fabricating to get new condenser mounted.

The 2nd option is leave it R-12 flush and replace o-rings you can use green ones they work with 134 and 12 then vacuum close off valves and verify it holds for 24 hours and add oil if needed you can buy R-12 cans on eBay 6 cans for $85. If you go this route I would replace the compressor and accumulator add a inline filter just so you know for sure it will work and you don't have to do it again in a year unless you know for sure that compressor is good. I would pull the orifice tube look for any metal shavings if there is any replace it. This is what I did with my 1991 Toyota pickup lasted 10 years in Phoenix heat 28 Degree air that was what R-12 could do it was amazing R-12 performance I sold it still working.

I have seen shops convert R12 to R134 with just o-rings, pressure sensors, accumulator and pag oil the only one I ever saw work decent was a shop that would remove the compressor disassemble it and clean out all the mineral oil reassemble flush everything add pag oil that was in 80-90- deg summer I live in Phoenix no way it would work that well here. You can get away with this if it's not too hot with large condensers possibly it might work on your larger vehicle.

I have done both I found the best way was to just leave it R-12 it was engineered to work with that trying to convert even replacing everything but the evaporator still not going to be as good as the original R-12 system.

If you do convert to R-134 it's not that hot where you are just replacing the o-rings, and pressure sensors at minimum make sure you get the old mineral oil out because it won't circulate correctly with R134 is my understanding causes lot of problems. The biggest problem is the old school condenser is not going to cool the R-134 enough the good thing is you can flush those old R-12 condensers the tube is not that small like the new ones today also replace the accumulator. Those old duel AC systems used a lot of refrigerant I remember my old 1980 C-30 quad cab pickup had 5 lbs system.

Quick ebay search $85 6 cans 18oz each > https://www.ebay.com/itm/6-XL-CANS-R12- ... dO&vxp=mtr

http://www.ackits.com/request-after-mar ... stem-quote Request a quote for aftermarket

I didn't look at that eBay link that carefully that isn't really R-12 it's compatible with R-12 I have never seen any of those work don't buy it make sure its real R-12 refrigerant not compatible stuff some of that R-12 retrofit stuff was flammable. https://www.ebay.com/sch/i.html?_from=R ... 2&_sacat=0

kell490 wrote:I didn't look at that eBay link that carefully that isn't really R-12 it's compatible with R-12 I have never seen any of those work don't buy it make sure its real R-12 refrigerant not compatible stuff some of that R-12 retrofit stuff was flammable. https://www.ebay.com/sch/i.html?_from=R ... 2&_sacat=0

Would I need less r12 if I did seal off the rear ac? And how much cooler is r12 compared to r134. Thanks again!

Wyattgc wrote:Would I need less r12 if I did seal off the rear ac?

Absolutely !!! And likely the new R4 compressor would last a ton longer. It's lower lifetime in dual-AC vehicles has been documented due to liquid refrigerant from the rear getting back into the compressor.

Wyattgc wrote:

kell490 wrote:I didn't look at that eBay link that carefully that isn't really R-12 it's compatible with R-12 I have never seen any of those work don't buy it make sure its real R-12 refrigerant not compatible stuff some of that R-12 retrofit stuff was flammable. https://www.ebay.com/sch/i.html?_from=R ... 2&_sacat=0

Would I need less r12 if I did seal off the rear ac? And how much cooler is r12 compared to r134. Thanks again!

Your system was engineered for R-12 if you were to only change the refrigerant to R-134A it could be 10-20F difference some systems did better then others the key to that kind of conversion is get all of the old mineral oil out which means flushing really well replace the compressor it's difficult to get the oil out of the compressor unless you take it apart and clean it out on a bench. Also need to replace the orifice, o-rings, and pressure sensors so your compressor doesn't cycle incorrectly as R-12 has different pressures then R-134A.

Yes if you block off the rear AC how much less refrigerant would you use I would not know if it was me I would guess 1/2 the amount to start with take some temperature readings from the vents should get 45F air Maybe someone who has done it before.

What's your goal with this vehicle want to keep it for next 10-15 years? Most of the time when I work on auto AC I just replace everything except the evaporator which I flush really well even if I'm charging R-12 if parts are still available. I know everything is new, clean, and seals good. I don't have to touch it for years here in Phoenix it gets so hot vehicle AC has to work really hard in Summer months like June 112-118 is common cutting corners with AC doesn't last one summer.