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1993 and older R12 R4 compressors vs. newer R134a R4 compressors

sctrailrider said:
I know this is a little old, but I saw you mentioned a adapter from R4 - sanden for PS compressors??? If there is such a thing, post the info, I'm changing out my AC now.....
Click to expand...

Small block V8. below. Brackets you can obtain lots of places. Hoses would have to be custom made at an AC shop that makes hoses. You could also get the 1998 belt drive system that uses a newer style of compressor as it will bolt on. Major changes to the alternator though. Never tried that.

http://www.classicindustries.com/truck/parts/346002.html
 
I'm replacing an R4 on my '95. The old compressor has a switch on the top rear, where the replacement compressor just has a blank plug.

Is this a high side cut off switch? Do I need to swap the switch over to the new compressor? I'm wondering if it's a high side cut-off, if it's redundant with the switch that goes on the new condenser?

I have the snap ring removed & not having luck so far getting the switch out of the old compressor.
 
Just got old switch out. & swapped it into the new compressor.

I replaced evap, heater core, compressor, condenser (got the slightly bigger Suburban dual air one), & new lines.

As I've got the entire front sheetmetal off for another project, I kind of wish now that I'd tried to find the '96+ accessory drive. Just fabbed a new sturdy mount to put a CS-144. Newer accessory drive would have mounted the AD-244 & the newer, better design A/C compressor. Got enough $ in new CS-144 & R4 compressor, so going forward.

But in hindsight, the newer accessory drive probably would have been a better way to go.
 
SmithvilleD said:
I'm replacing an R4 on my '95. The old compressor has a switch on the top rear, where the replacement compressor just has a blank plug.

Is this a high side cut off switch? Do I need to swap the switch over to the new compressor? I'm wondering if it's a high side cut-off, if it's redundant with the switch that goes on the new condenser?

I have the snap ring removed & not having luck so far getting the switch out of the old compressor.
Click to expand...
Yes, it's a high side cutout switch. No, its not redundant as the condenser switch actually switches the a/c to recirc once the high side pressure reaches around 325 psi. So you do need it. And the newer r6 compressor isn't any better.
 
OK, thanks. With everything new, hopefully that gives the best chance at decent service life. The new compressor is from GPD.

The compressor it replaced was getting a bit noisy at 210k miles, but looked original by the Harrison stickers, etc. Given the amount of shavings/debris the old system orifice tube had in it, guess the old compressor was shedding. If it really was the original compressor, 210k miles/15-20 years was pretty good life.
 
I've had REALLY good luck with GPD, and it's what is on my BURB right now. It's the ONLY ones I will use anymore. The chinese new ones are lucky to make it 3 months, and the mexico made remans are lucky to work out of the box, but the GPD's have been great for me so far.
 
The main issue here was hot trans oil in front of the condenser from running the oil through the air to oil cooler than radiator. This overheated the condenser and combined with a bad kick out switch on the back of the compressor kept blowing the system up. Thus that switch is critical on the compressor.
 
On my manual trans truck, I've moved the oil cooler to behind the skid plate (now ventilated) & have a thermostat controlled (or manual override switch) fan on it.

While I didn't do that specifically to avoid AC issues, suppose it should help AC performance a bit.

I have an electric fan I'd thought about using as a condenser fan, but the stack depth the DMax IC added doesn't leave enough clearance between the condenser & grill.
 
I have a SLIM electric fan on mine, and it JUST fits. Been on there for 6 years, and it's just now starting to not always work. Got a new 9" one to go back on it, but will be installing a pressure switch to control the fan this time instead of running it with the compressor.
 
Gather the pressure switch should run the fan when refrigerant temps are highest exiting the condenser so specifically when fan could do the most good? Imagine that does improve ac performance in the hottest weather when not moving, or vehicle just started to cool interior down. I'll have to see just how much clearance I have left. The fan I have is too deep, but think it's a 16" & not the slimmest design.

I held the rad to fan clutch depth to the same 1 1/2" as mine was stock - trying to keep similar dynamics in air temp thru the stack engaging fan clutch (upgraded the the spin on water pump & the medium duty clutch. The DMax IC & rad bolted together as they do. IC bottom mounted on the pins/bushing like you did. This put the condenser (moved toward passenger side like yours) touching the hood latch/horn bracket, so spaced it a couple washer depths forward.

I'm getting close to done & have considerable appreciation for how much work went into yours. Reading the threads of how others went about it help a bunch. Still lots of small details (body lift & 3500HD core support added some wrinkles & maybe benefits) that take time to sort out right.
 
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Revisiting this thread - this was a late conversion to R134A. Still seeing R12 OEM systems out there and recommend you don't convert as R12 is still available for cheaper than the "panic" years.

Regardless the Compressor clutch "diode" is 1-2' back in the wire harness on these years. The diode isn't in the clutch coil! So if you add the high side safety cut out switch (required for R134a conversions) you need to move the diode closer to the clutch or tie in after the diode. If you run the wires to the high side cut out before the diode the field collapse will arc weld the high switch shut. This was the 2nd part of my issue causing switch failures from no suppression diode and the excessive cycling from hot trans oil in front of the condenser.
 
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