It’s a '92 with the efan setup already, no?
'92 740 has the more efficient style condenser in it already, but not the yellow o-rings & later hoses (it might have those tho?) and chafed or cracked compressor hoses are common as is a cracked muffler tube if equipped.
Don’t mix your PAG oil w/ r12 mineral oil…that’s a
for long term longevity.
Totally get the ‘if the next guy has to service it or just top it up with cheap abundant refrigerant from brand-x’ concern, even if it means DuPont blood money/lobby with toxic inefficient refrigerant & scare mongering about a lousy few oz. of propane/isobutane.
Just swap everything from a 93+ n/a car or condenser from a 960 in it (the hoses to & from compressor & it’s pulley from a whiteblock is a no go, obviously?)
Various things you can't really easily entirely flush all old/used oils out of include:
-compressor (which is probably clapped out & marginal 150cc displacement to push R134A idling or otherwise due to wear, anyway?)
-Accumulator (inexpensive enough GM part new, anyway?) (even tho its just an alum pot with a dip tube IIRC when I cut them open, no desicant like the receiver-drier on a TXV system...just there to boil off refrigerant & trap any stray ice (shouldn't be any, really, if it was vacuumed down properly for an hour or more?), so the compressor doesn't ingest liquid refrigerant &/or ICE or the like?
-Trace mineral oil in any used R12 hoses (probably no biggie if you get a used R134 compressor pretty clean & use POE oil otherwise
(I worry about it but the R134 cars still seemed to go strong until something else failed)
-Muffler tube (if equipped?)
'Don on the glasses & good luck finding every little rat / trace leak (or micron gauge + nitrogen pressurizer w/dye if you know the right HVAC guy or happen to have other stuff that's R134 (air-source heat pump water heater?
)?).
R134a pressures are likely to exacerbate leaks, especially if it doesn’t have the later R134 holding hoses, tho I didn’t have issues with those holding the R34A in 90+ 700s I’d flushed/converted to R134 when not chafed or damaged?
But, also, most of those cars were for someone else & got a brand new R134A compressor, accumulator & tons & tons of flushing & subsequent vaccuum & charge W/POE oil (which is less slippery/efficient than PAG, but I worry about the R12 embedded hoses dissolving into toxic acid goo & ruining other high labor time $$$ to replace components).
Technically, the R12 mineral oil is inevitably embedded the hoses, so if you use a later used R134A displacement compressor w/any R12 other parts in the system, there's some risk there...it'll have some trace PAG in it & the hoses will have some R12 mineral oil embedded in them, inevitably.
Up to you?
Some later 7/9 cars don’t have the silly muffler tube…there’s a Volvo TSB on that iirc?
That's also another bit that IDK on my confidence to flush to get 100% clean...the Volvo TSBs & dealer conversion procedure don't explicitly tell you to replace it if equipped. I haven't if it wasn't leaking (yet
)?
But I know it can be a common-enough leak point?
Expensive new from the dealer when/if available...
Condenser from a 940Turbos doesn’t fit around the n/a airbox / no-go if the car is n/a.
The Volvo dealer r134 kit came with ester (POE, but not Edgar Allen) oil & oil-less refrigerant.
It was often prudent to use a more efficient condenser (if 240 & some earlier 700s, anyway), flush as much as you could (these cars often have been running around low on refrigerant with clapped out compressors, oil compatibility aside) w/ new R134a sized orifice & (healthy non-contaminated) compressor of appropriate size for 134a to have it work pretty darn well in our r12 700s…tho idk over the hot TX or AZ extremely hot pavement…
...that’s a lot to ask, but my sister graduated college & drove it back over 100 degree eastern WA desert in the summer solstice & it brain froze her & brain froze poor Ken/RWC when some tber broke his trailing arm tool & we had to dash to the only hardware store I knew was likely to have fine thread anything in those sizes on a hot summer weekend day & I drove a stock 744Turbo that ran ok w/R134 / no fuss?
The 240 dealer conversion kit replaced the evap, but not on 700s/same iirc between R12 cars since it has a gm/Harrison CCOT system same as the late 240s (which you can find parts for under the hoods or tons of junkyard cars (accumulators or whatever?)) & large evap already.
The Volvo dealer kit For TXV 240s essentially came with the 91-93 evap used in the later 91-93 cars with GM/Harrison a/c systems, but set everything up to work with the expansion valve system otherwise (which does use less energy/adapt to changing conditions somewhat better…but expansion valve can fail or clog or have a bad temp reference ether tube mechanicals control parts & more complex or fragile txv bits that can sometimes fail…).
Technically, the switches are different pressures between R12 & r134a as is the orifice size & compressor displacement…the latter two being the larger concern…
And the stupid fittings on the condenser & accumulator are different (understandably, they don’t want us &/or clueless hacks to Mix r12 & R134a parts/oils and to make some super toxic green hulk/moster chemical goo for service guys or toxic waste…this is common across most brands except the fords where the compressor will do either in the 90s-early 00s for most of them.)
(I only know this as I’ve all-junkyard converted the following vehicles that straddle the r134a (1993 for Volvo...they’re often early in model year for safety & federal regulations compared to competitors), 1994 for everyone else, usually, r134 federal mandate line:
-gen1 Subaru Legacy (1994 is last year)
-1981- ford full size trucks/brocos
-Jeep XJ (I prefer no airbag stripper models with less to break)
-rwd redblock volvos
-Toyota hilux (last year in USA is 1994, same as 1 year only for 240)
-Toyota previa.
-odd 87-91 Camry & some corollas mixing the junk drawer
-W124 MBZ
I refuse to buy anything new or any new China crap if I can help it.
So far, so good.
Tho hose crimp tools, hoses in common sizes & good tubing bender for a pro HVAC guy would be nice (& a better idiot than me/tool-using virtuoso to apply their talents using them, but I digress), but I just don’t do custom stuff enough to justify that…inconvenient & time consuming as another trip to the junkyard or hose shop or mocking stuff up is.
I’d use / keep the R12 brown primary fan switch on the condenser (lower pressure than R134A on the hi-side).
It might run the fan slightly more, but WWD Volvos use that size/compatible fan (tho the last of the turbo P80s had slightly quieter & more powerful curved blade versions of it?) + relay & still kinda litter the junkyards, & I’d rather replace Alts & fans a little more often than contaminated ground up prematurely worn compressors & A/C parts w/all that that entails?
I prefer the clutch fan & pusher, but for a driver/stock N/A late 7/9 beater, stock efan setup is fine...
You can use the SAAB T in the lower hose?
The idea there being that even if it loses some coolant from a minor leak that goes unnoticed, the fan still kicks on (tho the ECU runs it if the coolant temp signal goes absent after warmup on the Bosch FI cars) & install the later 960 'low coolant' warning lamp in a '92 740...I did for my sister & explained what it meant. Saved throwing a cylinder head or two in the scrap or more major breakdown!
SAAB T kinda sux if you live somewhere w/salt air (mild steel, but they rarely leak/rust thru...I sold most of my spares on here, but still have a couple & lower temp NOS quality W.Germany switches from old K-jet Audi foxes/similar eurotrash (tho I think I only have one spare 77-82C of those I'm hoarding)), but lower temp made in W.Germany switch is nice on the Regina e-fan cars in a lower location to stress the cooling system less...the regina cars have a push-in switch at the top left of the radiator (good location...unless it loses 1-2" of coolant from a slow leak you don't quite catch/doesn't drip on the ground, but I haven't found a push in switch w/temp any lower than the factory Regina push-in switch (which does fail sometimes...had a few cars w/totally blown heads & heater cores due to that cheap switch!)).
A little more fan run time & black coolant cap is kinda my preference? Lower boiling point than the green cap, technically, but less pressure to pop heater cores or swell hoses etc?
Worked good on my R134A 1993 no-sunroof, manual gray cloth seats hot-weather Hell.A traffic friendly stripper Regina N/A auto-trans 945 fuel sipper Regina contractor work van to thrash & abuse?
The lower temp switch upside down (works well as the coolant drain for the rad in place in the car)) in the SAAB T, black cap & installing the 'low coolant warning lamp' sensor in a not-cracked/too yellowed or old OE reservoir sure saved my butt a few times beating the hell out of that car!
In your shoes, what I’ve done is solvent flush the evap a ton & install a healthy (used & flushed as much as possible) 220cc r134 compressor & r134 sized orifice tube and flush everything else & use POE oil & pray?
So far, so good?
Tho, I still worry if some future tech shoots it with some PAG oil & there's any trace R12 mineral oil ANYWHERE in the system...I've seen the results of that...many, many times...black goo, corroded & acid eaten parts & lousy cooling...basically almost everything goes in the trash after that!
I forget, but I think you need a new accumulator w/o R12 mineral oil in it (cheap enough new, it is on a ton of cars that use r134 GM CCOT systems) & the compressor suction hose too on a 92 740 iirc?
Iirc that car already has the same style reasonably efficient condenser as the later 940s…works?
I *think* by '92 the orifice tube is relocated to the condenser liquid line & not at the inlet to the evap anymore like -'91? 700s…
Not all the variable orifice tubes fit in that location idk (if you want one of those for 'extreme hot weather & traffic'...they do work, but only if everything is squeaky clean & you get a decent quality one (tough anymore IDK...such as brand name means anything anymore?)?
And those can stick & jam if there’s any contamination/questionable used parts, so I KISS & just use a fixed tube if it’s not my car & there are more unknowns.
I'd just run an R134A sized fixed orifice tube & remove the lines/flush & clean them/inspect for lots of shavings &/or suspicious gunk on the orifice tube screens (usually there's an aluminum flake or two or a little glob or oil snot...that's usually fine/nothings horribly ground up or eaten).
Good luck to ya, all the guys up here ripped/sawzalled/death wheeled their a/c out & scrapped it 10 years ago...waste not, want not LMAO?
That said, things are getting warmer/dustier, but for a local coastal car you don’t need it more than a couple weeks a year really, but it’s nice when it works? Even for defrosting windows/humidity control?
You guys probably really need it down there…
This all said, I've seen hacks screw the fittings on after a basic flush/orifice tube replacement on a lower mile ugly R12 700 & suck it down & hit it with some POE oil & R134?
The later 700s with the more efficient condenser (even R12) cool ok w/R12 parts compared to the 240s.
Not great, but it worked/car was 'fine' if a little marginal at idle (despite running the push fan a bit more (lower temp/pressure switches to kick it on a bit more & a tropical fan clutch)...I think the lower displacement old probably somewhat worn out R12 compressor at idle can only do so much?
Longevity was
as it was a thow-away hideous $200 '88 764 w/some IPD sways & wheels to sell (so, -$ on day 1 of ownership
), who cares? IIRC ~48?F center vents @ idle on a 100 degree day digging thru old albums...pretty tolerable, ~40?F once under way.
Hideous utterly sale-proof car with tons of electrical to break & falling headliner & obscure weird IRS & interior parts.
Seemed to work for ~the 1-2 years/summers that car needed to?
Not the 27-28?F on the highway that a 700 GM A/C system is capable of, though? *almost* too cold (& very well might be somewhere super swampy humid & hot for ice formation if not set on 'recirc'...I suspect 28F in dry highway jaunts & is fine as there's probably sufficient space for ice to form on the fins & air to warm up to ~33 even on fan speed 1 & ice to melt just enough to allow air to continue to flow over the EVAP?). I never had problems, but it's dry by august/sept...infamously if you've seen the latest fires
?
Good luck, hope your daughters brains don't get cooked, a car of that age doesn't leave her stranded & keeps her safe.
Clear as mud, rite?
This was stream of consciousness, so it needs some edits to get rid of the repetitions & make a flow chart/decision tree for what standards you wish to enact a plan for cold R134A A/C in the daughters brick...
I'll also add that the front mounted/ducted HVAC box is really only got so much power to cool a whole station wagon in a brutally hot/sunny place.
Can be fine for the driver, & the center vents mostly reach the back seats, but its a lot to ask for it to keep 5 people on a hot day totally comfortable in a wagon? Tinted windows, driving less at mid day & tan cloth interior & breathable alpaca wool skinned front seats were helpful in gradmas car in the CA sun (tho bay area...not as hot as TX).