I'm going to be switching over my 1992 Bronco to R134a soon and have most of the parts to do the swap. I'm replacing the lines, replacing all the O-rings to R134 compliant, new drier, orifice tube(not sure on just using the Red one or going with a Variable tube yet). I may replace the Evaporator and the Condenser instead of just flushing them and I will keep the OEM compressor and flush it. The system didn't fail. I had it evacuated and it's still sealed and dry at the moment. I decided to do it because it needed a top up and I figured I will be keeping the Bronco forever(family Heirloom) ad may as well go ahead and convert it over to what all the other vehicle s have.

Now, in my readings, I've seen mention that one of the ways to "Help" the R134 work better in the old R12 system is to get a larger Condenser. I've been looking around online and really haven't found any. I noticed, though on Rock Auto that the parts between a 1992/3 and 1994-6 Bronco are the same size, specs etc.

So, does anyone know if there's a model out there that has a compatible but larger Condenser out there that I could install when I do the conversion?

Thanks

 

1994 was the first year for R-134a, so it's part # is different than that of a 1993 and earlier condenser. The 1994 was designed for R-134a, to have a larger surface area as a heat exchanger. If it has the same core size, and same mounting points as earlier, well, that's a great plus!
Core size is like a box... its the outer dimensions, but it doesn't describe the particular heat exchanger design INSIDE the box.

I don't know if the fitting size/sex/location are exactly the same or not.

Just a word on flushing a condenser... can't reliably flush any heat exchanger that has a parallel-path through it. Only true serpentine types.
Serpentine means one and only one path from input to output, like a snake bent back and forth.
Parallel-path means either:
1) A header on input end spreads out to many tubes, that go across and get collected back to one via a header at the other end (like a engine radiator). or
2) A combination of smaller serpentine paths, where serpentine paths are also in parallel with others.

 

I've been looking at the stock photos(if they are accurate) on places like Rock Auto and such and I do see the difference between the 2. It looks like there's about 27 rows on the R134 model and about 20-21 on the R12 model. THe connections, dimensions, between the 2 are listed as the same. However, the connections appear to be slightly different angles though the listed connection type is the same.


I may bite the bullet and buy both of them. they're listed for about $50-60 each so, if I save up a little extra, I won't feel too bad if I'm out a few dollars but have better A/C if the newer model can be made to work.


One thing I do see is the Dryer is different between the two styles. The R12 has the tube for the Orifice on it but the R134 model doesn't seem to show one.

 

I took a look at some of the parts on Rock Auto. I did see one pic that did not look right, visually the input and output tube sizes on the condenser were the same diameter, that would be wrong for a 1994.

Measured on my 1994 today:
- Condenser input (driver side) tubing OD is 1/2", has a 7/8" captive nut that spins free (when disconnected). Nut threads onto the HI side discharge line from the compressor, which has a threaded end with a hex to hold with a wrench.
- Condenser output (passenger side) tubing is 3/8" OD, has a 3/4" captive nut, same setup as other end, just sized smaller as the output of the condenser is liquid, whereas the input is vapor. The Liquid line attaches to the condenser output, then runs over to the input of the Evaporator.

The Orifice Tube is inserted into the wider-diameter portion of the evaporator's inlet, so it's totally hidden from view.

I looked at the 1992/93 Accumulator/Drier (A/D for short). The 1992/93 design is the style of A/D that Ford used for many years, it has the outlet of the A/D (gets hosed over to the suction port on the compressor) coming off of the bottom of the A/D, then bending upwards.
The 1994-on design has the A/D output coming out of the side, further up the cylinder, with the connection to the suction hose facing ~45 degrees back, like towards the passenger door, as a reference point.

I also saw that the 1992/93 A/D can either be bought with threaded suction line connection, or with Spring-Lock connection. So the HMA (Hose Manifold Assembly that has suction line and discharge line on a aluminum block that mounts to the compressor) and the A/D need to match fitting type, threaded or Spring-Lock.

A/D technology - The replacement A/D's that have been made for years now use a desicant that can be used with either R-12 or R-134a. The original A/D when the vehicle came from the factory with R-12 used a XH5 dessicant inside it, that was not friendly with R-134a.

So... I would use a replacement A/D that is for 1992/93, that has fitting type that matches your HMA.
So the last compatibility issue is to see if your existing condenser in and out fittings (therefore, the discharge hose fitting on the HMA, and the Liquid Line fitting), match the sizes I measured above for the 1994-on condenser. If they do, great!!!

If not... maybe look into the idea of changing the HMA and liquid line to a 1994 versions, but A/D will have to be a 1994 version, and would have to figure out mounting of A/D and if there is room for suction hose routing up over the evap box.

So I think the big ? is the 1992/93 condenser in/out fitting size and type, vs. the 1994.

Other bits:
- Will need a new CPS (Cycling Pressure Switch), which screws onto a Schrader port on the A/D, need a R-134a one (1994-on). The turn ON/OFF pressures, therefor temperature, are different between R-12 and R-134a.
- If you get all of the old mineral oil out, you can use PAG-46 oil, which is the standard R-134a compatible oil for these FS-10 compressors. If there will be some mineral oil left in the system, then POE (Poly Oil Ester) would be the oil to use, as it works for R-134a, and can tolerate some mineral oil dilution and still work properly.
- A R134a from scratch system has a HPCO (High Pressure Cut Out switch) screwed onto a Shrader valve port for it on the 1994-on HMA. The switch is wired in series with the clutch circuit. It drops out the compressor if something goes haywire and discharge pressure climbs over, say, 450 PSI. Other wise, if pressure goes over say 525 PSI, the blow-off safety valve opens up on the HMA mounting block, and recloses at some lower value. R-12 systems did not have a HPCO. Just about every R-12 to R-134a conversion does not have a HPCO.

There are many in the automotive HVAC community that will not use a variable orifice tube, having had bad experiences with them. They go with the standard Red R-134a orifice. I use Red.

 

Thank You VERY Much. I really appreciate the info and what you did.


I have a brand new(still capped) A/D waiting to go in when I replace everything. My new 92 style Hi/Lo side hoses came in yesterday and I looked at them and noticed they had what looked like the newer green seals at the connections. I'm thinking, at this point, I'll go ahead and get the new evaporator and condenser(94 model) and still plan to use the original compressor. I'll buy some more Dura flush and make absolutely certain the compressor is clean before putting all new parts back into the system.


I bought the A/D about a year ago from NAPA so I'm going to assume it has the newer style desiccant in it. I really don't know how to verify it, I'll take it out of the box and look it over when I get home to see if it lists it, but I don't recall seeing anything in the box or on the can saying what it was.


Thanks for the bit about the cycling switch. I'd meant to ask about that in the past and forgot about it. I'll get one ordered when I order the new Evap and Condenser.

 

One other thing.


Any idea what torque specs there are for the connections? I haven't heavily studied my Hanyes and Chiltons yet but a quick browse didn't turn up anything. Google wasn't much help either.

 

You're welcome!

I think it's safe to say that it has a compatible dessicant in it. But I would check to be sure that all openings on it are securely plugged. If one or more plugs are missing/fell off, then the dessicant inside has been trying to dry out the atmosphere for the last year, and will be tapped-out for further AC-system drying work
The CPS port on the A/D has a Schrader on it, so its probably OK without a cap in storage.

I would not try to flush a compressor with a solvent. There are a lot of places in the compressor where lubrication occurs: 5 double-acting pistons and their bores, front and rear bearings, 10 "shoes" (2 per piston) that ride on the swash plate to convert rotary motion to reciprocating motion.
I would tilt the compressor to pour all the old oil out of the compressor, turn shaft CW with a wrench while doing so, 20 turns or so will do it, Stand it up, pour in new oil, turn shaft, add some more, turn shaft, tilt, and turn shaft to empty oil again. Repeat oil flush routine again.
Do a final flush when you are ready to button it all up, as PAG oils absorb moisture from the air. Think of it as handling brake fluid, both are hygroscopic.

Torque specs from 1994 FSM:
Suction line to A/D 25-32 Ft/Lbs (irrelevant if yours is Spring Lock connection there).
Compressor discharge line to Condenser 15 - 20 Ft/Lbs
Liquid line at Condenser 15 - 20 Ft/Lbs

I never have found the torque for the big nut that couples the A/D input to the Evap's output. I have to use an open-end wrench there, and give it a good tighten, I'd guess at least 30 ft/Lbs by uncalibrated arm.
BTW... the O-ring in this particular connection is the biggest PIA in fitting things. If your replacement evap doesn't come with the O-ring (I have never got one), then you have to use the old O-ring to try to match it up out of the O-ring collection ($10 or so at Rockauto for semi-specific make/model). Knowing that the old O-ring will be squished, but yet, don't want to put a too-fat one in, and have it tear. Put a too-thin one in, it won't seal properly. On auto A/C systems, I think I can handle about anything... except trying to size that stupid O-ring! A lot of self-doubt when trying to match it up.

No torque value for bolt that holds the Manifold Hose Assembly to the compressor. Enough, but don't overdue it, it's not that large of a bolt, and it's threading into aluminum. O-rings are doing the sealing, but needs to be tight enough that engine movement can't work it around over time with the hoses attached and pulling on it.

Oh, and the 1994 FSM shows 7 Oz. of oil for total system oil charge, and that is what I used. It's PAG 46, but they show a motorcraft # instead, of course.

 

Great advice. Thank you for that. I'll pick up a couple more bottles of the PAG oil so I have plenty to flush through like that.

Checked the A/D when I got home, there was nothing listed on it anywhere. Went back to NAPA sight and the unit: TEM 208337 shows it compatible with R134a and R12 using the XH9 Desiccant so I'm good there. Still capped on all ports. I never opened it when I got it other than to look at it through the plastic bag. My Retro kit has LOTS of green O-rings and seals including a few spring clips but I think my system is all screw connect.

Thanks for the Torque specs. I couldn't find them anywhere in my books. I have the 2 different Haynes books, the older paperback Chilton and the old Green Library Chilton service book and none of them had it in there.

As a safe gaurd, when I first bought the majority of the parts, I also invested in a leak detector system and will put a little die in there when I put everything back together and refill it.

 

I converted my 89 to r134a, cools well with the stock condenser, used ester oil, it'll cool to 39 degree inside air temp on recirculate at 90 degrees ambient air temp. Does have a minor leak that it has to have a little added once a year. Put uv dye in, but haven't found the leak yet.

 

Good to know. Thanks for the info. Did you change the pressure switch on the setup or did you just evacuate the old and install the new refrigerant and oil to your system?

 

The pressure switch has an adjustment screw, it needs to be adjusted( search it, I've forgotten) but can be reused. My old compressor ran low on oil, it was replaced, system flushed, new accumulator, added oil, vacuumed down, added freon. Just had a refrigerant cylinder, don't know of a good way to measure, so we watched the pressures and slowly added until the temperature stopped dropping with the a/c on. If one knows of a more precise way to fill at home, I'm all ears.