E_S

I'm working on fixing the AC system on my '87 GTA. In the process, I'm changing over to R134a.

I know the R4 compressor has got a really bad reputation and changing to another compressor is recommended. Thing is, I live in a place where AC isn't something you MUST have (a nice summer day means 80F and summer lasts a couple weeks..), and most of the reason I fix it at all is that I can't stand having equipment that is not working correctly.

I'm thinking of sticking with the R4 compressor and just replacing the receiver/drier and all O-rings. AC will of course be used, but it is not important for it to be very "powerful".

Any very good reasons to spend several hundred $$$ on upgrading the AC compressor, or would it be okay to stick with the R4 for such "low-intensity" use?

sofakingdom

iTrader: (1)

It's not "bad"; just, kinda fragile by modern standards, and not very efficient.

It fails in strange ways. One of the oddest is, the entire outer shell of it, is a sheet metal can, that slips over the internal cast-aluminum guts; and the tabs that keep the can from sliding on too far, are welded to the can, and the spot welds crack and leak. And of course, the O-rings that seal the can to the main pump body, are like 7" dia (around 160mm or so I guess) and fail often.

If you're changing to R-134A, replace ALL the O-rings, including the seals where the line assy bolts to the back of the comp; and of course, the 2 large ones I just mentioned. Use the medium PAG oil (75 - 100), not the 50 or the 150. Use the red/orange Frod orifice tube, such as, for a 96 Crown Vic or the like. Flush everything (metal lines, evap, cond, comp crankcase) thoroughly; use lacquer thinner, MEK, acetone, or denatured alcohol. NOT brake cleaner, "paint thinner", mineral spirits. Use something that evaporates 100.000% and leaves no residue. Replace the rubber line sections and use REAL A/C hose clamps on it, NOT the little weenie "heater hose" ones. Pour about 2 floz of oil into the comp suction port and about 3 floz into the accum/dryer. Evacuate to within 1" of deep-space vacuum for at least an hour, remove the pump, let sit for another hour, if the vac fails to stay within 1" of where it was before, find and fix the leak(s) and repeat the evac process until it DOES hold. Put in 4 cans of R-134A, which is probably too much; but THIMK, more R-134A isn't gonna just materialize out of the atmosphere and add to what's in there, all it's ever gonna do is leak, so it's better to start out with slightly too much than "perfect" let alone too little. And of course make sure your cooling system is perfect, especially, your radiator fan moves LOTS of air.

Reid Fleming

iTrader: (2)

Stick with the R4. They work fine. They have the ability to run as cold as anything else out there. They're a bit noisier than new compressors. But that's about it.

You won't need to switch to the red/orange orifice tube in Norway. The stock white colour will do fine. You could switch to the blue if you wanted. But for your climate, there is not much point. White runs best on the highway (lowest hi-side pressure) It tends to lose performance at long stop lights. Blue is better in the city, slightly worse on the highway. Red/orange is best in the city, worst on the highway. It's a trade off.......But still, with Norway summers, I doubt you'd notice any difference among these.

Fast355

iTrader: (2)

I run R152a in my Express van with a 25% underdrive on the crank. The rear expansion valve is stock and the front orifice tube is a Red. Even on a 105°F day it cools well at idle around town. On the highway it can nearly freeze you to death. The GM white never cooled as well even with the factory crank pulley and R152a. I had to retrofit an adjustable cycling switch into my application because the evaporator would freeze up every 20-30 miles with the stock non adjustable unit.

1986_IROC-Z

Subscribed. The R4 in my '86 was disconnected when I bought it last year. Appears to be completely original, probably still has some R12 in there unless there's a leak. (looks like the pulley failed, lots of issues there).

Also interested in a R134a conversion, unless I can find R12 to put back in there.

Also curious to know how I'd go about flushing the system (probably needs to be done anyway after 30+ years?).

The dealer quoted me $1000+ for a new compressor, flush, conversion, so I'm tempted to figure this out myself or get to the root cause if it's something simple.

paulo57509

I've done a few conversions and a few flushings. It can turn expensive real quick to DIY. This is because there are no band-aid or half-a$$ repairs with AC systems. It's an all or nothing, do it once correctly kind of deal.

IMO, $1000 seems reasonable to have someone do this for you.

LiquidBlue

Do you still recommend medium PAG oil, everything I've read on a conversion is to use ester oil, because the mineral oil from the R4 compressor residue will react with the PAG. However, ester oil has some disadvantages in that it will absorb moister and create acid. Other than that, everything I've read is to use PAG 150. I'm thinking if one flushes the compressor (along with all other lines) you could flush out the old mineral oil maybe?????

These guys cover the different oils and discuss ester issues:
https://www.tecumseh.com/~/media/Nor...n-of-R134a.pdf

Page 7-8 POE/PAG oils - how residual R-12 chlorine effects:
https://www.jstage.jst.go.jp/article.../37_3_226/_pdf

Excellent discussion on mixing oils and what type of oils to use. Next link is actual studies performed (found that while searching for the SAE study, 3rd link)
http://acsource.net/acforum/viewtopi...179ec7be990079
http://infohouse.p2ric.org/ref/27/26070.pdf
https://www.sae.org/publications/tec...ontent/940599/

http://www.underhoodservice.com/ac-c...s-differences/
http://acprocold.com/uncategorized/pagoil/

When exposed to high levels of moisture and heat, POE (Ester) may undergo hydrolysis, causing it to revert back to its original components of acid and alcohol. (so POE is a ester according to these guys) This also discusses flushing, and say that it is not even recommended by some manufacturers.

Not all PAGs are Created Equal
The unique, patented, double “end-capped” formula of PAG provides exceptional chemical stability to the oil. Ordinary PAG is still chemically active while “end-capped” PAG is chemically inactive or stable. Even at high temperatures, the “end-capped” PAG is very tolerant of moisture and will not react to form harmful acids.
http://www.autoactech.com/issues.htm

Double End Capped PAG oil study. Bottom of 5th page, this study implies that the chlorine in CFC-12 provides lubrication that 134a does not possess, and can provide lubrication to the compressor when their are lack of oil events that can occur inside the compressor.
https://docs.lib.purdue.edu/cgi/view...0&context=icec


They are recommending PAG 150 for GM R4
http://www.autoactech.com/PagOil.htm
https://www.aa1car.com/library/pagoil.htm


Flushing discussion
http://www.autoactech.com/flushing.htm
http://www.teamec.be/cms_files/Flush...eaning(EN).pdf
https://www.hella.com/techworld/uk/T...C-system-1891/

These guys claim studies show that residual mineral oil protects rubber hoses designed for older refridgerants
https://us.bergstrominc.com/images/K...ofit_Guide.pdf

Flushing video - how the pros do it
https://www.hella.com/techworld/uk/T...-system-1891/#
https://www.robinair.com/products/power-flush-solvent

FLUSHING PRODUCTS
http://www.comstarproducts.com/produ...lushing-fluids
http://www.ecompressedair.com/compre...anerflush.aspx
https://www.qwik.com/


Make your own flushing system????

http://shurflo.com/industrial-produc...12-2088-series

Since these are non-pressurized liquids, the technician must purchase a pumping device such as a motorized chemical-acid-oil pump to circulate this chemical throughout the system. A hand oil pump can be used on small applications. While most chemical pumps do an adequate job of moving the coil flush throughout the system, the seal and diaphragm materials that come in direct contact with the coil flush must be considered. Seal and diaphragm materials such as neoprene, santoprene, nitrile, and polypropylene have a limited compatibility with some coil-flushing agents. Swelling or deterioration may occur that could cause pump failure, and/or leaks, and/or requiring the replacement of the impeller, diaphragm, O-rings, or valves.Pumps manufactured with Viton® or Teflon® appear to be the most resistant to the chemicals that make up the coil-flushing agents.
https://www.achrnews.com/articles/86...ical-for-coils

Search "Diesel Transfer Pump or Oil transfer pump". Wondering if a large fish aquarium pump would get the job done. Ya, probably toast after the job, but who cares for the price.

FLUSHING THE COMPRESSOR

nice write up on flushing your compressor with oil and bench testing your compressor
https://autoacforum.com/messageview....threadid=12050

POE oil as a solvent to remove mineral oil?
http://www.refrigeration-engineer.co...in-compressor&

ability of POE oils to be effective detergents. These oils can effectively clean the inner surface of a system, releasing debris that might be present....
https://www.achrnews.com/articles/10...es-forethought

Getting the impression PAG and POE are somewhat compatible and will mix. Thus one may be able to first flush compressor with POE, and the flush again with PAG in order to convert directly to a PAG lubricated system
http://newsgroups.derkeiler.com/Arch.../msg00948.html

Removing oil from system - page 16
http://www.rses.org/assets/serviceap...l/620-1071.pdf

Compressor cleaner flushing discussion
https://oil-services-lab.com/flushin...ting-procedure
http://www.ecompressedair.com/compre...anerflush.aspx

We’ve performed several in-house tests proving that even miniscule amounts of residual impurities can manifest into mineral acid burnouts. Service technicians are scratching their heads wondering how a newly converted HFC/POE can burn out in just several months of operation. If the old linesets were retained, residual impurities are the main suspect. Remaining lineset particulates, acid, moisture, and mineral oil can combine into a sludge that’s similar to molasses. To ensure complete removal of the flushing compound, it too, must vaporize. Therefore, any un-pressurized liquid flushing solution from a jug is totally unacceptable, since it’s just trading the oil and other non-evaporating fluids in the system with another liquid impurity that also won’t evaporate. Given the complex chemistry interactions of HFC refrigerants and synthetic oils, this is a really bad idea. Instead, only flushing compounds that vaporize should be used, which means they are packaged in a pressurized disposable cylinder or pressurized aerosol can.
https://www.contractingbusiness.com/...0a-conversions

Compressor oil change out procedure
http://chevron.novacomportal.com/pro...2_20160420.pdf

According to this Mobil Rarus 800 can be used to flush old mineral oil:

Hit download button to open document.
https://www.mobil.com/en/industrial/...ir-compressors

https://www.petroliance.com/sites/de...0%20Series.pdf

https://www.mobil.com/English-RU/Ind...rus-800-Series

Various flushing procedures are provided by the compressor fluid suppliers. For example, when switching from a PAG/POE to PAO, or vice versa, use a diester to flush the system and then fill with the new fluid.
https://www.efficientplantmag.com/20...r-compressors/

Ultraclean claims to flush mineral oil:
http://pdf.ultracheminc.com/ULTRACLEAN_GUIDE.pdf
http://ultracheminc.com/cleaners-chemicals/

Patents on system like Ultraclean
https://patents.google.com/patent/US5452586

MISC

Blurb about Harrison R4 compressor from Hemmings
https://www.hemmings.com/magazine/hm...s/3703521.html

Nice write-up on 3rd Gen Firebird r134 switch over - amounts to complete A/C system change - handy guide even for flushing
https://www.hotrod.com/articles/how-...vaporator-case

Good discussion on Pressure switch - I'm leaning towards leaving stock in place until all other avenues exhausted, as the R4 was likely designed for a certain pressure range.
https://www.thirdgen.org/forums/cool...-pressure.html

Discussion on 25% of all warranties due to wrong oil used by garage and how much oil is in each system component
http://www.denso-am.com/products/aut...ompressor-oil/

Excellent overview of how automotive A/C system functions, diagnosis, repair and maintenance
https://www.omega-usa.com/client/ima...%20HVAC101.pdf

A/C Training manual
https://www.macsw.org/WEB/images/Mac...anual%20LR.pdf

Demonstration on why not to use mineral oil

ULTM8Z

Agreed. Unless you have the equipment and know how to use it, it'll get expensive and frustrating.

I helped a friend restore his A/C system earlier on. But I had all the equipment from when I bought it used during my aftermarket A/C retrofit on my 2nd gen, so I already kinda knew what I was doing. You can rent these types of tools from Autozone though... vacuum pump, A/C manifold gauges and hose, flush kit, etc. But I had him go to the local shop for flushing and charging (I didn't want to take a chance on his car with doing it myself).

Changing the parts isn't that tough... new hoses, orifice, compressor, o-rings, etc... It all just "bolts together" for the most part. It's the rest of the process that is crticial.

You just have to get the flushing right, since if there's debris left over from potentially an earlier compressor failure, you'll ruin the new compressor (hence the expensive part). When I flushed my own system last year after my compressor failed, I literally dismantled the entire system, ran the entire gallon A/C flushing fluid through the hoses, evaporator, and condenser, and then followed it up with generous flush of acetone to ensure zero residue. Then let it all sit out for a couple of days to ensure no solvents were left over before reassembling everything. Also bought a new drier (which is must since you cannot flush them) before putting the new compressor on. Also need to get the right amount of correct oil for the compressor (underfilling can ruin the compressor, whereas overfilling can reduce system efficiency by taking up volume that would ordinarily be filled with refrigerant).

Then the charging part... drawing down a vacuum, ensuring no leaks, etc... don't want to screw up here since refrigerant is expensive if you have iterate. Then getting the right system pressures (I wouldn't trust those "built-in" gauges on the cans of refrigerant you get at the local auto parts store). You need to monitor both the low and high side pressures.

I don't know... if you don't mind learning (potentially by trial and error), and you're mechanically inclined, you could attempt the job on your own. But if you're just looking to get it done the first time, $1000 may be worth it.

R4's are ok. I ran one initially since I have a GM serpentine belt drive on my 2nd gen, but then stumbled across a thread on this site on how to convert to a Sanden FLX5 or FLX7 compressor (which is what my system is meant to run with). The R4 did ok and blew cold air (~42°F, which is pertty good). Though the Sanden doesn't rob as much power off the engine, is quieter (you can't even tell when its running) and now blows 36-37°F air, clearly the system was designed to run with the Sanden. But sounds like for what you're doing, the R4 is more than adequate.

If the hottest day over there is 80F, a properly running R4 system should freeze you out of the car.

tom86iroc

iTrader: (1)

i put my system together with all new orings and oil and had my ac shop do the rest best 100 bucks i spent to swap over worked for over 15 years till the compressor seal in the front let go