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AC Accumulators - whats the diff?

15A

15A

World's Oldest Brewery
Joined
May 7, 2004
Location
OH-MI....just like it sounds
Admiral Rebel said:
One was probably designed with R12 refrigerant in mind, and the other for R134. They serve the same purpose.
Click to expand...

Something I wondered myself.

So do you think the one labeled for 91-93 is R134, and the 86-93 is the R12?

Only major thing I see is an extra orifice/port on the one.
 
swede242 said:
Something I wondered myself.
So do you think the one labeled for 91-93 is R134, and the 86-93 is the R12?
Only major thing I see is an extra orifice/port on the one.
Click to expand...


That was my line of thought. Earlier ---> R12 (or universal?), later --> R134

That being said, the system in my 1990 740 wagon was R12. I used one of those cheapo conversion kits sold at Advance Auto parts, ensured I bought sealant and PAG oil, and recharged my system 3 years ago. Still works fantastic.
 
The late cars use an aux pusher fan and different pressure switch arrangement. They also use an orifice tube arrangement with the dryer pictured (like a GM/harrison) instead of the expansion valve setup used on 78-1990 cars (in various flavors) with the in-dash thermister style dial switch.

They achieve the same thing, but the pressure switched, orifice tube system cycles the A/C clutch according to the switch on the dryer mounted near the firewall panel. The operator just turns the single toggle "on" or "off" on the dash. Look at a pic of the engine bay of a 91-93 car if you can. 1993 is the first and only year of R134.



The old system, we have a relay triggered by the thermister dial thingy and expansion valve mounted on the passenger core support sheetmetal. You turn the dial and it cycles the a/c clutch according to how cold you want it. The manual advises that you leave it on continuously for the first bit and then turn it down to prevent icing or undue wear.

If you want a 240 series and want good reliable A/C, rip everything out of a 91-93 car if you can. Easiest is just to change out the old york compressor (on 84 and older), convert the filler to something nicer to use and enjoy the nice quiet integrated plastic reservoir 91-93 style PS pump. However, EVERYTHING is much better laid out in the late cars as far as A/C goes, and that means changing everything over...blower box, passenger firewall panel, lines, brackets, compressor, electric fan and fittings and the larger condenser used on those cars. A GM/harrison universal variable orifice tube (fits in the volvo) and some duracool make the things really work well. I personally keep the dial switch in older cars, but I am not an electrical wiz and I am a bit of an electrical minimalist.

Beware 93s...they are R134, but the biggest biatch is that some genius at volvo decided to change the thread on all the fittings. Same purpose and everything...I swear, the newer cars get, the more ways the bean counters find to screw the customer. A/C and 240 was more or less an afterthought, so I'd try to make it fit and work as best you can with careful addition of late model stuff as you deem necessary and go from there. I was fortunate enough to have a cooling technician help me out with it all and make sense of it. I can't say I am looking forward to laying it out real clean and nice and not busy in my black california 245TI. The little differences in all the A/C parts and the A/C not being so cool in the first place in most 240s except the latest ones makes it a real challenge.
 
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945ti said:
If you want a 240 series and want good reliable A/C, rip everything out of a 91-93 car if you can.
Click to expand...

Exactly what I'm doing. I pulled the entire unit from a 93 - right down to the firewall and am doing a thorough conversion in my 88. Wiring is actually quite straight forward once the 2 systems are laid side by side. One of the major differences was that the later AC units get a signal from the ECU - my guess was for an idle increase when the AC was activated. The older 2.2 boxes also have a similar "signal" that is unused. As of now I haven't tapped it in but did run a wire to the ECU area in case I do.

Its not an easy swap but IMO will be worth it. So far I have an NOS condenser, evap and compressor. I have the accumulator from the 134 93, but was contemplating needing one of the ones pictured......now I think most likely the 91-93 drier.

Thanks very much 945ti and the Admiral for the clarifications.
 
Accumulator is used with an orifice type system, such as 700/900, and late 240. It is located near the firewall,a big silver canister. The orifice tube is in the line near the frame rail on passenger side and not visible in use. A reciever/dryer is used in a TXV system (thermostatic expansion valve) ,like the early 240. TXV systems have a valve located under the dash. This valve has a copper tube and a small bulb which sits in the evaporator fins, and is connected to an adjustable switch on the lower dash. Some early systems had no adjustment. The reciever drier is a little black canister located near the condensor at the front of the car,next to the radiator. It has a sight glass on top, a little round window in the line.

The type of refrigerant is immaterial to the type of system. R12 or R134a can be used in either one. The accumulators can not be used in receiver/dryer systems and vice-versa.
 
Wow, That's great! I didn't think that anyone else was attempting this conversion except for me. I'm converting my '84 system with a system from a '92 that's already been converted to R134 freon. I'd like to know what you figure out on the wiring on this project. I'm at that point now and I'm weak at best at these wiring diagrams in the Bentley manual. I do have one question and maybe I should start a seperate thread but there's a green wire that goes from the switch on the accumulator to the ECU in the '92 and I've stared at the wiring diagrams for the '84 and I can't figure where to run this wire to in the '84 system. I imagine it has to go to the ECU on the '84 somewhere. I don't want to just start hooking things up to the ECU and damage some part (or all) of it. Please let me know what you find out on this. Thanks, Charles
 
15A said:
Exactly what I'm doing. I pulled the entire unit from a 93 - right down to the firewall and am doing a thorough conversion in my 88. Wiring is actually quite straight forward once the 2 systems are laid side by side. One of the major differences was that the later AC units get a signal from the ECU - my guess was for an idle increase when the AC was activated. The older 2.2 boxes also have a similar "signal" that is unused. As of now I haven't tapped it in but did run a wire to the ECU area in case I do.

Its not an easy swap but IMO will be worth it. So far I have an NOS condenser, evap and compressor. I have the accumulator from the 134 93, but was contemplating needing one of the ones pictured......now I think most likely the 91-93 drier.

Thanks very much 945ti and the Admiral for the clarifications.
Click to expand...

LH2.2 has a "signal" for the idle speed with the A/C on. In the 4-pin connector in the engine wiring harness near the ECU it has 3 critical wires. A red/black which is the 12V power feed from the ignition switch and turns on 1/2 of the fuel pump relay, the yellow/blue which is the power feed to the fuel pumps (fatter wire as well), and the thin red wire which ties into the a/c/fan switch that is fed 12V with the A/C on to raise the idle speed to 900rpm. I like my H-cam 12:1 SCR flat top piston B23E clone to idle at 900 and jumper that pin (non-A/C DL). I am not certain how LH2.4 works in that regard...not sure those cars raise the idle speed with the A/C on...it isn't as obvious as the LH2.2 cars if they do.

Yeah, I've put everything minus the switch change in earlier cars. It is definitely involved. The switch and electrics look fairly straight forward. I'd need to stare at the 93 donor car, green book and maybe a 7/9 series to fully wrap my brain around changing the switch/relay setup. That, and the early stuff worked real well with the late mechanical stuff so I left it. John Lane has done the conversion on a few cars too, but I think that mostly meant just changing the compressor and PS pump for people so the system would actually work. Nice thing about early cars is that they aren't quite as gadget filled under the dash for the most part. 86-88s are my favorite to do heater fans on quickly...
 
I converted a TXV(early style) to R134a and it was ice cold. So it is not necessary to change the sytem completely. Volvo has a kit, but you don't need everything. Just get a TXV valve for R134, some new o-rings and some ester oil. The kit has a new receiver/dryer in it, but some are having good results re-using the old one. I would flush the condensor out to make sure there is no debris. Add some ester oil to the compressor(check specs). Then have your system vacuumed down and checked for leaks. Add ester oil charge to the R134a as recommended. Ester oil is important to use when upgrading, as it will mix with any residual from the original. PAG oil is also used, bu t doesn't mix as well with the old stuff.

Early on, the thought was that if upgrading, you had to replace major components like condensor and evaporator, but now, good results can be had as long as the original items are in good working order.
It is important to have the system vacuumed down to remove all traces of water vapor. and to add the correct amount of oil and R134a charge.
If done right, this conversion will blow ice cold. I had 38* air coming out of my vents.
 
The PO of my 88 was a savage.....my guess is he had a unibrow and arms that drug on the ground. The only tools in his box was a hammer and crowbar. He removed the condenser and destroyed the sheet metal surrounding it.....so I got all new (JY) from a 92 and replaced that. He/she/it also bastardized the dash wiring.....so thats all coming out anyways - and a mint 93 dash/frame, blower box, diesel sound deadening pads, etc is going back in. Will also have the heater core cleaned/pressure tested and the wiper linkage cleaned/lubed while I'm in there.

I picked up an NOS 92-93 evaporator and condenser for next to nothing, so those are ready (my 88's condenser was gone to begin with).

Whenever I redo my AC, 99% of the time I get a new refurb compressor for about $120ish from Tommy Wong in CA - so thats ready to go in as well. I do this because twice I spent the $$$ to have a shop redo my AC only to have the compressor crap out 12-18 months later and had to start all over again. Only thing "used" is the high / low pressure lines, as well as misc brackets.

But 38* AC? Wow...........my 90 765 blows 50 and I thought that was something.
 
Hey Mike Sr., What do you use to flush the condensor out with? I thought that I'd flush it as well as the lines to be sure all of the debris is out. Thanks, Charles
 
The only difference in those dryers is the schrader valve for fill/evacuate the system. On the early systems the service valve was on the back of the compressor, and at some point systems w/R12 they put it on the accumulator and moved the orifice tube to the line, instead of the firewall. To my knowledge most of the GM type systems with the valve at the compressor were found on 740's as early as '85, but few made it to a 240 since the expansion valve system was on up to ~'90.
When you convert to the later system be sure you get the accumulator and compressor that is for 91-93 and run the line from evaporator to accumulator with the overpressure valve loop, and the line from the condenser.

Also the best accumulator is one that hasn't sat on the shelf for years, or isn't in a sealed package.

I used Quick-Solve. It's a much cleaner solvent than the petrolium type solvents, and works better. I found it at an A/C supply place.
 
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