I researched the difference between a 1992 R-12 Aerostar and a 1997 R-134a Aerostar. This was after my compressor locked up and threw the belt. I will summarize some interesting points unique to the Aerostar's A/C system that will be useful to owners of any year:
1)The factory Ford FX-15 (motorcraft) compressor was used on all R12 Aerostars, Taurus's and Rangers is truly a piece of crap. It is the most unreliable compressor EVER made and the ONLY one on the market that can not tolerate the elevated pressures of a R134a conversion. It is no longer manufactured and has been superceded by the FS-10.
2)The Ford FS-10 (motorcraft) compressor has been used on all R134a Aerostars and it works fine with R12. It is a marginal design and a descendent the FX-15. It is sold as a new replacement by many mfrs, simply reboxed motorcraft. Unicla makes a totally different design that is a direct fit. It has almost no track record, so buyer beware.
3) Rebuilt FS-10 compressors are hopeless. The design is marginal, so rebuilt units are not capable of performing reliably. Many remans see so many warranty returns that they've chosen to sell new motorcraft compressors in their reman box. These can be a good buy.
4) A locked up FS-10 or Fx-15 will cause what's known as black death. This is a situation where the compressor superheats and blows particulate throughout the system that sticks to everything. It looks like rough carbon buildup inside an exhaust system and it spells future failure. To prevent recurring failures, you MUST replace the oricfice tube(s), condenser, accumulator and thoroughly flush all hoses and evaporators with the appropriate cleaners (Ford recommended Terpene found at Home Depot or approved A/C cleaner). If you have rear air, the rear filter tube must be replaced.
5)The job is a nightmare and parts can exceed the book value of the vehicle.
6)In 1996, Ford upgraded the condenser assy to a oval tube, high tube count unit. This was designed to lower high side pressure, improve efficiency/performance and extend compressor life. It is a good upgrade, but be forewarned it is not a direct retrofit. The manifold hose assy that bolts to the compressor was altered where it attaches to the new design condenser. The liquid hose from the condenser to the rear evaporator was altered in the same manner. In both cases, they upgraded from Ford's leaky spring couplers to a stud/bolt setup. This required me to install a different hose end on my rear liquid line where it attaches to the condenser. The line can be removed and taken ot a hydraulic hose shop by opening the motor inspection plate in the vehicle's interior above the cup holder. Both rear A/C lines are in two pieces with couplers under the carpet-covered inspection cover.
7)When you're done, you have 1996-97 style cooling (the ultimate). Was it worth the extra money and time, I dunno. My van now chills passengers when set to low at 95 degrees.
8)When Ford upgraded the Aerostar to R134a, they also added shrouding and air deflectors around the radiator and condenser. If you look, you'll notice the rad sits about 2" behind the condenser. On the R12 vehicles, there is nothing blocking air from being sucked through this gap and through the radiator. This means less flow through the condensor. The condenser efficiency rises if you seal this crack with foam on both sides and the bottom. I built a "shelf" from formica and glued 2" foam to it above the swaybar. Ford did the same thing using semi-rigid plastic.
9) In a cost comparison, the better '96-'97 condenser costs $188 or more and can only be bought thru Ford. The older round tube condensers are about $70 less. If you buy the better condenser, this forces you to get the '96-'97 compressor manifold tube assy for about $150. In addition, you must change the connector on the evaporator liquid line going to the evaporator(s) which can set you back another $50. This adds almost $300 to the rebuild for the '96-'97 configuration.
Cost summary: New Motorcraft FS-10 Compressor, $220; New Manifold Hose assy for '97, $150; New '97 style Condenser, $190; Accumulator, $75; liquid hose mod, $50; Ford rear C-pipe with integral filter, $70; O-ring and garter spring kit, $20; Castrol PAG 46 oil, $16; 30 lb bottle of R134a, $120; R134a Gauges, $100.
Christ, that's $1000 invested in my $3K van.
hope this helps someone avoid pitfalls.
Q
I have a '92 Ford Taurus SHO with 94,000 miles on it with an R12 air-conditioning system that's never been worked on. In very hot weather in stop-and-go driving, the A/C effectively stops working after some time. Recently, after 15 to 20 minutes of stop-and-go driving on the freeway, the A/C suddenly started blowing warm air. I investigated and found that the compressor clutch was cycling on and off about every 10 seconds, but after 17 minutes it cut out and the A/C got warm. I then headed out on the road and the A/C returned to normal. Is the system low on refrigerant? Has it degraded over time? Is the evaporator icing up? Or is there a problem with the pressure switch?
A
From the symptoms you describe, evaporator icing is a real possibility. When the system works so hard to cool things off on a very warm, humid day, condensation can freeze on the evaporator, eventually forming a layer of ice that prevents it from absorbing heat from the cabin area. This also can occur if the system is overcharged with refrigerant.
Have you checked coolant operating temperature with the vehicle idling? Perhaps engine temperatures are climbing to the point where the engine management system won't allow the compressor to engage until things cool down a bit.
Another possibility is a weak compressor. At low engine speeds, such as stop-and-go driving or idling at a stop, the compressor may be unable to keep up with the demand from the system. Or perhaps debris is blocking the expansion valve or orifice tube that meters refrigerant into the evaporator.
I'd suggest having an air-conditioning specialist such as Dealer Automotive Services in Hopkins check the system. For less than $50, they'll test the system to identify the problem. Then you can decide how to fix it.
If your system needs major service -- which I'm hoping it doesn't -- it's worth considering an upgrade to R134a. The cost of this upgrade, not including repairs to your existing system, is about $200. Eventually, this is the way to go because with R134a, you're dealing with refrigerant that costs about $10 per pound, professionally installed, vs. more than $50 per pound for R12.