I decided to upgrade my R4 compressor to a Sanden 508 compressor. I used adapter brackets, made custom hoses using short drop fittings to provide hood clearance, replaced the accumulator, a new cycling switch calibrated for R134 and a variable Orifice Tube and finally a slightly longer serpentine belt (Gatorback now made by Continental). I had a local AC shop evacuate and charge the system. My AC blows colder than it ever has even when it was charged with R12. This was on my 89 S14 Jimmy 2WD with 4.3L

 

I was expecting this to be an OBA setup!

 

I had to look up OBA as I was not familiar with the acronym. OBA=On Board Air. My Navy Background has OBA=Oxygen Breathing Apparatus. My 2000 GMC Jimmy Diamond Edition has a factory rear Air Compressor for keeping the air shocks at the right ride height but it also has an connection for an Air Hose to use to fill up tires and inflatables.

 

Sandens are indestructible. Had one on my '72 El Camino - was an aftermarket under-dash system built specifically for that car, some time in the late 70's to mid 80's. Was a TXV system, so that compressor ran non-stop anytime the A/C was on.

Ran that thing for 11 years - several trips back and forth from Phoenix to Livermore, CA, the Grand Canyon, Nogales, MX, and a trip cross-country to MA, then several years of commuting. Was still dead silent and pumping perfectly when I sold it in '11.

I had rebuilt that compressor in '00, and installed a parallel-flow condenser as big as I could squeeze in. Ran Freeze-12 in it, as it was designed an r12 system. Wanted the lower pressure stuff, since every hose was held on by hose clamps (never had an issue with them). Stuff worked great - had mid-30° vent temps in 110° Phoenix heat. System was amazing! Had such a high heat demand, with all the engine heat that used to flow straight into the cab as if there were no firewall. You'd never know it with it turned on.

Just when I thought that system couldn't get any better, I charged it up with propane out of my grill one day. Thing blew air so cold, I had to manually cycle it to remove the ice from the evaporator in 90° super-humid air. Like sitting in a freezer in a supermarket in the summer. Pressures are super-high with that stuff, so I went back to Freeze-12 when I had the dough.

Great choice in compressors!

 

So is this upgrade a major undertaking?

 

If you source the parts needed individually, no. I purchased a kit for a V8 truck and it bit me in the A$$. I thought I would just need to make up hoses. You would need:
1. Compressor, 2. Mounting Brackets, 3. Accumulator, 4. R134 Changeover Kit (O-rings and Service Ports), 5. R134 Cycling Switch. 6. R134 Variable Orifice Tube. 7. AC Beadlock Fittings, barrier hoses for suction and discharge hoses. (I used short drop fittings for the compressor side for hood clearance.) I would buy and install all items except the hoses and let an AC shop crimp the fittings on to the hoses and evacuate and charge the system. (Rock Auto, EBAY and Internet (R4 to Sanden Brackets). ROCK AUTO for Accumulator, Orifice Tube and Cycling Switch. Ebay for AC Fittings and Change over kit. Internet search for A4 to Sanden brackets

 

Arizona Mobile Air, Inc. | Automotive Air Conditioning Parts & Equipment is one of the best places on the planet for A/C parts. They're spendy, especially if you're on the East coast, but they stand behind all their products. That said, they don't have everything, especially when it comes to hoses on older vehicles. They also have THE BEST forum on the PLANET - Automotive AC Information Forum - ACKITS.COM - , especially if you're just starting out, or, have a really difficult problem to solve. The guys on there know their stuff. I've been dealing with them for 16 years. I trust their compressors more than ones from the local auto parts store.

I recently did a complete overhaul of the A/C system on our '86 Grand Marquis. New EVERYTHING, then charged up with R12 / mineral oil - the way the system was designed. This system blows ice cubes, and the pressures on the high side never get above 170psi on the hottest of days. Used Nylog on all the o-rings. Should be set for at least 10 years, since all the hoses are the modern barrier type. I got some of the hoses at ackits.com, and some at RockAuto.

I'm now in the process of planning out the restoration of the A/C system in our '93 Volvo 940. I'll be doing that one R12 as well. That one is proving much more difficult to find replacement hoses for.

 

Update: It is starting to heat up in Southern MS and my AC is blowing colder and more efficient than ever and I am the original owner of my 89 S15 Jimmy. The Sanden upgraded consisted of: Compressor, Receiver Drier, Variable Orfice Tube, Cycling Switch Calibrated for R134 and new barrier hoses and fittings. The engine does not bog down at all when the Compressor kicks in. It blows cold very quickly at start up. I did have to put a slightly longer belt as well. A++++++ on the upgrade.

 

Thank you for the info and images for the Sanden Compressor Upgrade. I have long wanted to change from the factory R4 and after my 3rd leaking R4 unit in 5 years I decided to switch.. The images and info were very helpful, sorting out the mounting system and Serpentine Belt alignment are time consuming. My system was converted to R134 about 5 years ago. My S10 Blazer is a little different from yours, has a 4.3L Vortec and 4WD. On the Vortec V6 the area behind the compressor is a little different, must navigate a molded heater hose from the front passenger side of the intake to the heater box and also a molded PCV Line. I almost purchased a Sanden 4864 compressor (FLX7 Series) and believe that I could make it work with the Dingo Bracket but decided not to because of the greater length. I think this model (4864) does include a Flyback Diode for the clutch and I may add that if necessary to the 4711 I ordered. It also includes a pressure relief valve that I would like to have on the 4711. I am hoping to get a little better gas mileage with the Sanden, the R4 can cost me 3mpg on the highway. I am considering changing the Pressure Cycling Switch to optomize for R134a, may get one of the older adjustable switches and set it where it works best for R134a.

I expect to get the parts and make the conversion in the next 10 days or so. That would be just before labor day 2022.

 

It seems like the easiest way to convert yours would be with the accessory brackets and related parts from a later model 4.3 that already has the upgraded compressor. I'm pretty sure the junkyards are full of them.