I know this is not on a F-car but a similar era GM AC system I am starting to work on. Since I am running into the issues that most will trying to upgrade and rebuild their older GM A/C system, just throwing this up to show how to overcome the issues for the build and get a system that performs better than new, despite not running R12. The drop-in replacement condensers for GM vehicles this age have become a total joke in fitment and capacity. I am correcting that with this setup. I am upgrading it to get ice cold a/c and already know it will perform based off prior systems I have set up. My rule of thumb is a clean, well sealed evaporator core that forces all the airflow through it, the largest parallel flow condenser that will fit, efficient compressor upgrade and an orifice tube size adjustment.

I already swapped the engine to a L31 and used its bracket setup, tossed the junky R4 compressor to the side, removed the ancient, inefficient and damaged tube and fin condenser. I pulled the blower resistor, took a peak into the evaporator core housing, jam packed with leaves. New evaporator core, new blower motor. Bought a replacement condenser that was supposed to be a drop-in for the application but ended up being made wrong and was tiny compared to the available core support opening. I know parallel flows are more efficient but they made the drop-in unit smaller than the OE tube and fin by a substantial amount.

Since I would be fabricating mounts for it anyway and new hoses made up, took some measurements of the available space. Did some research and found a condenser for a Peterbilt application that will mount easily, has the correct #8 & #6 fittings, covers nearly the entire radiator opening in the core support and will mate to the OE liquid hard line. The Peterbilt replacement condenser core is 420 sq/in vs the 312 sq/in of the "drop-in" fit replacement. I actually contacted the company selling the "drop-in unit and their head of engineering only wanted to argue that it was in fact correct despite pictures showing it was not.

I will have the hoses made up in a week or two to mate to the Vortecs HT6 style aftermarket upgrade compressor and get it working. I am going to end up using a Sanden 4261 HT6 replacement based off the SD7H15 compressor that is a common replacement used. The OE vortec compressor mounted high pressure cutout switch is also getting wired into the compressor clutches ground circuit to cut the compressor should the ac high side pressure ever reach an unsafe pressure.

I am using a Vortec 4.3L S10 fan and heavy duty fan clutch for more airflow through the cooling stack. the more airflow you can move through the condenser the better. I also use a Ford Red 0.062" orifice tube in place of the GM White 0.072" tube on everything GM I run. Since many of us own other GM products, the GMT400 trucks with condenser mounted orifice tubes can also use an early 90s Cadillac FWD car orifice tube that is condenser mounted with the same 0.062" orifice as the Ford Red. R134a and R152a actually remove more heat per unit of refrigerant boiled in the evaporator, but need the refrigerant flow reduced so that the evaporator pressure stays at a lower suction side pressure, especially at idle. With the larger GM spec orifice tube the low-side pressure will not drop enough at idle and lower vehicle speeds to provide good cooling. The orifice tube size change is even something that has worked well in my OE GM R134a systems like my 97 Express and 99 Tahoe. I love being able to get ~30F air out of the vents before the compressor cycles even on a 110F day.

Given the Express and Tahoe are running dual evaporator systems and reach those vent temps with essentially the same compressors and similar sized condensers, the single evaporator system should effortlessly reach them as well and probably even have better idle cooling. I will take more pictures as I progress, but this is where I am at with the system at the moment.

I am basically starting over fresh with new system components and upgrading inexpensively where possible. The compressor itself will always be the highest cost item, more than the rest of the components combined, so it pays off to get a good quality unit and replace the other compenents at the same time. Cleanliness is probably the most important thing. If you plan to keep the hoses and hard lines be sure to flush them multiple times and blow them out multiple times to ensure all the flush solvent is removed. The flush solvent can contaminate the system if not properly removed resulting in poor performance and/or physical damage to the system. You also want all the mineral oil left in the system removed.

I intend to cover every aspect of this rebuild, from the tear down, fitment, fabrication, installation, flushing the hard line, to the actual evacuation, charging and cycling switch adjustment to get the coldest air possible.

 

First up condenser install. Took about 1 hour taking my time. Even with the grille in place the massive condensers presence is hard to ignore.

 

I have not forgotten this rebuild. Just had to wait for parts and have been out of town. Headed to Colorado this week too. However an update on this custom build, ac refresh.

New evaporator core and blower motor installed, underhood HVAC case are re-installed. Orifice tube is installed and the liquid line flushed and connected. The condenser and evaporator core ends are capped off to keep things out of the installed parts. Last week, I ordered an inexpensive hydraulic actuated bead lock barrier ac hose crimper, hoses and fittings. Tested the crimper, crimping the two fittings on the discharge and suction hoses that will connect to the condenser inlet and accumulator outlets. I will cut the hoses to the final lengths before they are crimped to the universal Four Seasons 12034 ac manifold. Red Ford 0.062" orifice, part number 38635 is installed as well.

 

I was looking at one of those crimpers. Looks like it produced a pretty good result.

 

Seems like a solid result, very quick to setup, and easy to make the crimp. For my occasional use, no need to go buy a $550 US made equivalent when the $115 Chinese version should last me through multiple projects. It was also cheaper to buy the tool than pay the local AC hose shop to make the 4 crimps. Wanted $30 a crimp plus materials for 2 minutes of work.

 

Are you planning to charge this thing with R134 or R152?

I just did a full AC system on a G20 van a few months ago, and I used R134 and a Ford .067 orifice. It got really cold.

 

Since it is mine and I am the only one that works on it, R152A. The nice thing about that, if the vehicle ever gets sold, I recover the R152a completely, vacuum it a bit to make sure 100% of it is gone, then charge with R134a. Did that with my 2012 Titan that had R152a in it and my 2011 M56S. The R152a is a drop-in for R134a with no changes to anything. It should have different fittings, but I am not worried about anybodies recovery system getting contaminated with R152a because I am the only one working on these systems and I have my own inexpensive dedicated recover system for R152a. I bought a pair of old analog Robinair recovery units from the Nissan dealer I worked out that were tossed out because they had to buy computerized machines with temperature probes to print a little printout to make warranty claims. Memory serves me correctly, I only gave ~$150 ea for the old Red Robinairs way back in 2011ish. Anybody repairing ac on a regular basis needs a recovery/recycling unit and a functional, used system is a very budget way to get one. The old analog ones just seem to keep working as long as you change the recycling filters.

The G-vans usually do pretty well on R134a, but I feel like R152a will give it a little edge on a 115F day.

 

very cool ...I was thinking about revamping the AC on my '91 G30 box truck-the cab is partitioned off from the cargo box,so small area to cool.

 

Condenser is equivalent to part number 3S010633. Liquid line screwed right in after mounting it, but the compressor discharge hose has to be custom built. I would probably ditch the R4 with a rebuild and go with a Sanden anyway. The universal sandens are cheaper. The other possibility is using a V5 or V7 for a 2.2L S10 and adapting the R4 brackets to fit.

I picked up the bulk hose by the foot and fittings here.
https://coldhose.com/

 

Years ago,i had grabbed an R4 from a '95 S-10 as a spare-thinking the "bugs"had been worked out of the design after ~19 years of R4 production...Fittings at the back are slightly different on the 95 R4 as i recall-,I have some V5s and Sandens that could get deployed too.

 

The later R4s are better than the earlier ones, once you get past all the sealing washer/spacer stuff needed to adapt it to the manifold hose. That being said they still fail in the same manner as the older ones, blowing refrigerant out of the case seals, vibrate, rattle and eat power. Adapt over a V5 or V7, put the lowest pressure control valve in it and you are getting somewhere. V7 moves more refrigerant at full stroke than the A6 does and the V5 is just behind that. With proper control valve selection can hold the evaporator temperature near freezing without having to cycle. I start with the lowest pressure valve and work backwards if the evaporator tries to freeze with the V5/V7s. Much smoother operating compressors and eat a lot less power going down the road when they de-stroke.

 

David that was a participant of the old GM EFI mailing list ran a V5 on the R4 bracket on the L03 305 TBI in his older Nova.

 

I finished this project a while back. Even with the engine cover off, the ac gets very cold. It was about 85-90F when I charged it. With the engine at 2,000 rpm it got down to 29F out of the center vent before the compressor cycled. At idle the center vent was running about 40F and the RH vent right at the evaporator core, away from the engine heat was about 36F. System should work very well once the engine cover is on it and some weatherstrips are replaced.

 

I like the digital pressure tester....it even has a FUN button!

Great results though. 90* already down there....yikes. We were still getting snow last week.

 

Yea its getting warm down here especially in the afternoons. Snowed a couple of days while I was in Pagosa Springs last month. Was a fun trip.

Here is our forcast this week. One of the reasons I have gotten good at this ac stuff.



I cold started the van, before the engine heated up, it dropped to 36F out of the center vents at idle. Going to be plenty cold I feel. Might still be a smidge low on charge, but I will see how it does as it warms up here. Being a custom system have to charge off pressures and temperatures. I do need to pull the dash to gain access to some other stuff anyway, I will clean out the ducts and reseal them all while it is apart. The vents have a good bit of foam like material stuck to the back side of them, assuming it was the mesh behind the evaporator core that was missing that I replaced with the newer metal mesh and chunks of the duct seals. I can also feel numerous air leaks from the degraded foam seals between the ducting sections. I use closed cell foam adhesive backed weatherstrip and the high temp aluminum duct tape to seal them up. As it is probably blows 2x as hard out of the vents as my friends C10 the same year. I figure his has a dirty evaporator core and the blower motor is likely not getting good voltage. It is LS swapped but the wiring was not upgraded like this one was with a new junction block. The blower motor on this is only seeing a 0.3V voltage loss from the battery voltage.

 

My wiring no longer feeds off a 10 awg off the starter with the tiny undersized junction post typical of GMs of the era. It has a 6 awg feed off the battery and matching size charge wire off the 145a AD244 alternator. All fused with the correct gauge fuse links. Picture taken with the protective cover removed.

 

Since I finished up the engine work, wiring harness, header install and exhaust work, the engine cover went on and I have been driving it the last 2 days everywhere I go. Cools quickly and gets cold, especially cruising down the highway. It will get down to ~30F out of the center vents at highway speed. After the initial cool down, the 2nd fan speed notch is enough to stay cool in these sunny 75-80F humid days we are having. That was idling around town.

 

Fast,those are some impressive vent temperatures! Summer is already arriving here in south Texas.

I've got pretty much the same AC hose crimp tool that you have. I'm sure its made in the same china factory. It worked great for my custom fit hoses in my LS3 swapped, 1991 Foxbody Coupe. I'm getting sub 40F vent temps using R134a.

 

Is in north Texas too. Was sunny, warm and humid the other day, put 100 miles on this. I did end up having to turn the cycling switch adjustment in 1/2 turn as the evaporator was starting to freeze up with the air from the center vents reading a near constant 30*F

 

Replaced the a/c cycling switch that was malfunctioning and the fan clutch that was acting goofy with a Hayden 2786 severe duty to get proper airflow across the condenser. Checked the engine and a/c cooling. Engine is now staying under 200F even after it idled and ran for close to an hour with the ac on. It was 92F outside and 32% relative humidity. FSM chart shows at 90F and 30% R/H, should be at 51*F with R12 or 57*F with R134a and it is cooling mid 30s and no longer freezing up the evaporator core. AC is working far better than GMs minimum performance chart and I have not even hooked up the heater core control valve yet to stop the coolant flow to it using recirculate. I have never owned a vehicle that stopping the flow of coolant to the heater core did not positively effect the ac duct temps. Even with good seals on the flapper doors, the heater core is a ~200F heat source in close proximity to the ac ducting and partially re-warms the air you are working hard to cool.

I started the front flooring today to cover the bare metal left from removing the nasty old carpet. Started with a layer of sound deadener insulation. The whole front floor pan is now covered with the material even under where the swivel seat bases mount. Then jute and it will have a thick vinyl mat over the top. The rear will have a solid deck of plywood and covered with layer of thin foam backing for the laminate flooring that is going in the back. After that the rotted old headlining is coming out. I have already discovered very little insulation to the roof and will be addressing that as well. The final step will be limo tint on all the side and rear glass to help shed the sun load. Hard to cool something adequately in the summer sun that is not well insulated over the engine compartment, firewall and roof as well as has enough glass to be a greenhouse. Properly insulating heat out of the cabin and reducing sun load through the glass makes a HUGE difference in interior comfort. I recently found a heat rejecting film that is not tinted and thus suitable for windshields as well. Will probably add that when the new windshield goes in as well.

 

Now that it has gotten full blown summer in Texas I added a GMT400 truck 11" electric condenser fan with its control relay tied into the orange high blower relay signal so that it runs when the a/c blower is moved to the highest speed setting and ended up optimizing the charge in 105F a few days ago. Ended up adding about 8 oz more refrigerant to get the superheat at the accumulator outlet where I wanted it. Retested the ac again today in 101F and a swampy 40% relative humidity. Driving around DFW it was blowing low 30s and would peak at 29F before the compressor cycled as long as the engine was over 1,500 rpm and about 44-46F at idle.




Video clip I made testing it out. It is blowing COLD. So much for the people claiming one needs R12 in a R12 era vehicle to stay cool. This system would honestly blow colder at idle if it were not for the limited capacity of the SD7H15 even with the 4.25" pulley and 8" Vortec crank pulley. It is a 155cc displacement compressor. My 97 Express has a Four Seasons 88947 10 cylinder HT6 with 210cc displacement and a 4.2x" pulley. It moves a lot more refrigerant. The 10 cylinder 210cc compressor holds pressures equal to or better than the Sanden pulling a dual evaporator system where this is a single evaporator system.

 

Ended up swapping out the JUNK Sanden SD7H15 for a Denso 10S20F. Went back to a GM White 0.072" orifice tube with the 200cc compressor. Performs much better at idle speeds and plenty cold running down the road. Was 98F and 65% relative humidity when I was testing it this afternoon. During the test drive it was dropping to high 20s center vent on high blower, recirculate and saw as low as 26F before the compressor cycled during a 2,000 rpm performance test after the interior cooled down. The evaporator core was draining water off it like crazy, looked like a coolant leak rather than condensation drraining.

10S20F for a 2003-06 4.3L/Duramax uses the same bolt pattern as the Vortec 350 HT6 style 4261 Sanden replacement compressor I was running. It has the same guts as the low mount 10S20F LS truck compressor. Definitely a good compressor to retain doing a LS swap rather than a POS Sanden. Uses off the shelf and inexpensive LS compressor hose adapters. The 10S20F is quieter, smoother, seems to suck less power, and moves a lot more refrigerant especially at idle (10 cylinders with 45cc more displacement than the Sanden). I was holding about 36-40F at idle rather than 45-50F that the Sanden was doing before even with the smaller orifice tube.




Installed with new fittings from Cold Hose. The high side has a 10mm switch port. Using a 20051 Four Seasons pressure switch now for fan control but will be a GM trinary pressure transducer later on to feed a LS PCM.


Pressures at idle, Flexalite 4,600 cfm fans running at 60%. I still have the 11" pusher fan that runs with high blower speed selected. I removed the relay to test and it still benifits the setup with the Flexalites.


Pressures at 1,500 rpm. During this test, the coolant climbed to 210F and the Flexalites were screaming at 100%.



This was holding 2,000 rpm after my ~10 mile test drive. A F-car even a T-Top or Convertible or C10 would be a meat locker with this setup. This one really needs a rear evaporator to help cool the interior volume although it gets very comfortable up front even with only the front dash ac.



https://youtube.com/shorts/HuM5zCOVnyY?si=3ykD4kxC87GrX11h

 

Fast, this is very interesting information. There's so much info there that I'm going to have to read it several times to absorb it all.

You post has my mind is spinning because I ***thought**** that the genuine Sanden compressors were THE compressors to use. Here in the Houston area, I need all the AC cooling that I can get.

For my current LS7 swap IROC, I was planning on using ICT Billet front accessory brackets.. These brackets are for the Sanden compressors. I'd be willing to use a Denso 10S20F but I have no idea if it would bolt up to the ICT brackets.

 

The Sanden SD7H15 is 155cc displacement and mine had the small pulley they list for use with the Express van application rather than the larger pulley listed for GMT400 trucks and SUVs. The LS truck compressor is 170cc for front air only or 200cc with rear air. I have the L31 Vortec brackets on this so the newer 03+ 4.3L and Duramax used the same compressor mounting style. Just drove around town, stopped at Sonic, ordered a burger, and ate it with the engine idling and the ac blowing. The sun is beating down, it is over 100F and about 38% humidity at the moment. Driving down the road even at 35-40 mph, I saw the center vents dip into the lower 30s. At idle it stabilized around 40F. My previous testing with the Sanden was with a clutch fan. The 4,600 cfm Flexalite electric fans do not move as much airflow as the clutch fan even idling. Idling my coolant temps crept up over 215F today where they never ran over 203F with the clutch fan. If I still had the clutch fan on it the ac would cool even better with more airflow across the condenser.

 

I had someone say there was no way I was getting vent temps like I am. So I checked and calibrated both of my mechanical thermometers to 32F. They were both pretty close, within 2-3°F. Easy to check, let a cup of ice water stand ~10 minutes, shake it around a bit until it is a consistent temp throughout, hold the hex on the back, turn the face until the dial points to 32F with the temp probe in the ice water. The calibration on my cheap digital IR meter is not adjustable unfortunately.

 

This has been a good thread. Been following it the whole time. I have made fun of Fast355 before for his van obsession, but I actually think this is a pretty cool van and the build info is useful to anyone looking to improve an old system. Thanks for sharing.

 

Anyone who makes fun of @Fast355 because of his vans is a ****ing idiot. That guy has done a **** TON of engineering exercises on his vans, which have the same drivetrain and components as the F-Bodies. And GMT400s. And a bunch of other GM cars.

He's very scientific with his methods, and he gives detailed explanations about everything he does. He thinks outside of the box.

 

Can't even give people a compliment anymore without triggering some snowflake. Legitimately thought people would appreciate me giving Fast355 some kudos. Oh well.
But at the risk of triggering someone else I'll say it again: nice A/C work Fast355.

EDIT: And cool van, too. Thanks for sharing.

 

Thanks!

It is actually pretty fun to drive too. I enjoy being back in a G-van at times. I have had all kinds of vehicles over the last 20 years and it is good to be back in a something GM with a basic old small block which both this G20 and my 97 Express have. The 383 in my 97 has a bit of a twist to it which this 87 will also soon have. I traded off some EFI Connection 24X parts including the brackets for D585 coils that they no longer make. My buddy is dropping an 8100 in his 95 GMT400 and pulling the small block that stuff is on. I have a deal worked with him to get that stuff back after he drops the 8100 in.

My 97


My buddies 95. I am also getting back my first Mercruiser MPI dual plane manifold. I plan to throw a 4L80E in it in place of the TH400 at the same time it is down for the 24x swap and perhaps the Comp 218/228 on a 108 LSA cam I had in the 383 in my 97.

 

I think you both are saying the same thing, lol. I did not read any hate toward this project just toward others hating it.

 

After doing a lot of online research yesterday evening, I think that I figured out that Sanden has two different mounts: DIRECT and EAR. It appears that I want/need the ear mount as I think that's what most of the aftermarket brackets are designed for.

Fast, the Denso compressor you posted a picture of in post #22 shows what Sanden would call the "direct mount." That would be difficult for me to mount to my engine unless I had the actual brackets L31 Vortec brackets which I do not have. Not only that, but my engine is an LS7 and not a SBC.

I think that I'm going to have to stick with a Sanden. Unlike my LS3 swapped Foxbody, I'm going to use a parallel flow condenser for my IROC. That should give me better efficiency vs the 1991, OEM Ford, R12 condenser that I used in my Foxbody (R134a.)