Steve85

I got the AC routing worked out and ended up with the compressor to condenser line (orange in above pic) going under the compressor and the compressor to accumulator line will follow the blue-to-red path. To go this route, I need to relocate the hood prop which is fine, the later model hydraulic props are much better anyway and designed to be on the driver side.Trial fit pics are terrible so I'll get better pics with final install.

The fittings are a bit different than most common crimp style, I went to 5 shops that crimp lines (mostly hydraulic) and responses were either "we can try, but no guarantee" to "they don't fit in out tooling". I had to send a bunch of unused fittings back to Nostalgic AC anyway so I sent the lines I made along with the returns for them to crimp.

What I realized is that a lot of these places sell fittings and hose that will work for AC, you just need to use the correct type of O-ring. So if you're doing custom lines (or no longer available replacements) call around to your local hose makers, I wish I would have done that first. Go in, buy a few fittings and some hose (you won't need more than 3ft of either size), mock them up on the car and bring them back to be crimped and return unused fittings without all the shipping and what not. The other thing is the hose that the aftermarket AC places sell is the same outside diameter for #8 and #10 hose and with installation space at a premium, the thinner OD #8 hose might have helped.

I should get the lines back Mon/Tues and then get going on final hose install, compressor wiring, and system charging.

Steve85

TL;DR - AC works!



The full story:

Electrical:

So I was checking all the wiring to make sure nothing was inadvertently removed during the swap. I figured I’d be OK since there was only limited connection from the body harness to the engine control harness to begin with. The only connections were really to alert the ECM that the AC was active but the ECM had no control over the AC.

I was tracking voltage and continuity and getting confused. Pretty sure it’s because the FSM has a couple of pressure switches labeled incorrectly.

According to the two diagrams below, I should get 12V to the “High Pressure Cut-Out Switch” with the control unit on Max / Norm / Bi-Level. And, that HPCO switch is on the lower evaporator line, closer to the firewall. What I observe is 12V on the one labeled as “A/C High Pressure Switch”.





I also find continuity from the AC fuse, through the control head and to the switch labeled “A/C high Pressure Switch” and then from there to the “Pressure Cycling Switch”.

It really makes sense since the two switches that are in-line to control the compressor are identical in size/shape. The other switch, meant to control the cooling fan through the ECM, is much smaller.

Now that the diagrams made sense I was able to correctly wire in the new compressor clutch pigtail by rerouting the output side of the Pressure Cycling Switch to the compressor as the 12v feed. Then simply wired the other side of the compressor pigtail to a suitable ground. I still have a few things to figure though, although none of these are preventing system operation.

1. The Pressure Cycling Switch alerted the ECM that the compressor was running, my guess is to bump the idle to compensate for the load. I’m pretty sure I don’t need that with the LS engine since it has a MAP sensor that should detect the load and adjust idle accordingly. (No MAP sensor, only MAF, on the original engine) - EDIT: Idle only drops about 150 or so RPM when clutch engages, so I'm think I'm good here.

2. The High Pressure Switch would tell the ECM to run the cooling fan if pressure on that line was between 100 and 233 PSI. Temporary solution will be connecting directly to the fan relay with a more permanent solution going through the PCM. I’ll need a programmer and someone who better understands the LS PCM capabilities better than I do for that though.

3. This compressor was designed for low RPM engines, like real low. Redline on the original TPI motor was something like 4800RPM. The recommendation is an RPM switch that will disengage the compressor clutch (if otherwise engaged) at about 4K RPM. I’d prefer to do this through the PCM but same situation as #2. Until then, it’s not like I go redline all the time, if I’m doing an autox or something where I’ll be above that for any period of time I’ll likely have the AC off anyway.

Installing the Lines and Charging the System

I got the lines back Nostalgic and they looked great, perfectly aligned with my marks and ready to install. I started to second guess whether it had actually been converted to r134 since the fittings for the manifold gauges were not 134 sized fittings and there was a mix of black and green o-rings even though the hoses that were on the car when I bought it, were clearly aftermarket and 134 compliant. I started poking around some more and found this blue orifice tube. Apparently, converted GM systems work better at lower RPMs with the blue "Ford" orifice tube, there would be no other reason to have a blue one in this car.



Feeling better, I went ahead and oiled up the o-rings and installed all the hoses and the accumulator. Since I never removed the other components from the car (condenser, evaporator) and was careful to not spill the oil out of the compressor or accumulator, I felt pretty confident I didn't need to add much oil. I added about an ounce to the suction side line (big one on top) for a little insurance though. I decided not to flush the system either since everything was removed in working order.



Get out your big boy wrenches



Looks pretty factory!



Installed the r134 fittings.



Installed and ready to be charged. I picked up some manifold gauges and an air operated vacuum pump from HF for less than the price of one hour of labor for someone else to do it. Of course if you get it wrong and nuke your compressor, gonna wish you paid someone.



The process is pretty well documented in various youtube videos. I watched a couple over and over so I could get the process down in my head. At a very high level, it's pretty straight forward, just need to make sure you're square on which valves to open and close and when. There were couple times during this process some refrigerant spit out (purging) so make sure you have gloves and eye protection!

Wall of text process I followed:

1. Connect hi (red) and low (blue) side fittings to car, open valves.
2. Connect vac pump to yellow gauge line
3. Open valves on manifold
4. Connect air line to vac pump to begin evacuation
5. Recommendation is 30 minutes, I did 15 since I didn't flush and my air compressor was running constantly to run the vac pump.
6. Low side gauge should hit 28-29" of vacuum pretty easily indicating a leak free system.
7. Close hi and low valves at the manifold and turn off pump.
8. Monitor low side gauge for about 15-30 minutes, there should be almost no loss of vacuum, it definitely should not be dropping steadily.

If all good with holding vacuum, continue:

1. Leaving all valves as is, remove vac pump from yellow line and connect to a freon can. (You'll need a valve that goes on the can that pierces the top and has a connector to the yellow line)
2. With the can pierced and the valve on the can open, slowly loosen the yellow line at the manifold to purge the line of any air.
3. Start car and set to max AC. (I think this typically engages the cooling fan and/or condensor fan to maximize air through the condensor and keeps the system working it's hardest. If you have a mechanical fan or the max AC feature is not wired up yet, use some other fan pointed at the grill, I used my "Blue Blower". It was interesting that the vent temps where 5 degrees cooler at idle when the my blower was running so it definitely has an impact!)
4. SLOWLY open the blue valve at the manifold, freon will begin to flow into the system. (My compressor started cycling on but for very short stints, as more freon got in the system, it stayed engaged longer and longer. The pressure on the low side will cycle at like 45 to 55, and as freon is added the range drops)
5. It may be necessary to slowly turn the can horizontal on occasion to get the freon to flow into the system. Not a good idea to turn it upside down quickly and flood the system though. Help it, don't force it.

To switch cans -

1. Close blue valve at manifold
2. Slowly disconnect yellow line from can valve (I covered with a rag to prevent any residual spray)
3. Put the can valve on a new can
4. Connect to the yellow line
5. Open the can valve
6. Purge the yellow line at the manifold again
7. To resume charging the system, slowly open the blue valve at the manifold.
8. Repeat until you have added the proper amount of freon (for a conversion, you use 80% of the recommended R12. My car calls for 44oz of R12, I put 34oz of r143. It should take 35.2, but I went with 2 11oz cans and a 12 oz can for a close enough. I already had 3 11oz cans, which is why I didn't do 2x12 +11)
9. Monitor vent temps and low side pressures. (novice advice here, my high side gauge stayed at 0, not sure why but the system was operating so it had to be something with my valve positions. I was so worried about "DON'T OPEN THE HIGH SIDE" that I didn't mess with it. Also, all those recharge kits in the store ignore the high side.)
10. Vent temps should down in the low 40s
11. Low side pressure should cycle 30ish to 45ish (Exact pressures depend on a lot of factors but almost every video I've seen and my own experience, is in this range)

To stop charging -

1. Close the valve on the freon can
2. Close the valves at the fittings attached to the car
3. Close the manifold valves
4. Disconnect the valves from the car
5. Remove the can from the yellow line (might be some leakage here, use caution)
6. Open all the valves on the gauges to purge everything (I really didn't get much, if anything, coming out)

That was about it!

Some tidbits I learned along the way:

• r134 hates being overcharged, too much in the system will reduce performance
• A blue orifice valve is a good idea for a GM system converted from r12 to r134, especially if performance is poor at idle/slow speeds.
• It's just a process like anything else, not sure why I waited so long.
• If rewiring the compressor, it definitely needs a solid ground. Also, confirm circuit flow through the pressure switches.
• The amount of air being pulled across the condenser has a big impact on system performance. If you've installed a smaller fan, an underdrive pulley (mechanical fan) or anything that would reduce this airflow, it will impact the temps you get from the vents.
• I used the same PAG 150 oil that the previous owner did since it was already in the system and apparently OK. I did see some caution around using PAG in a conversion that it can react with left over chlorine in an old r12 system. My system was open so long and previously converted so I went with PAG 150 with UV dye. If you're doing a conversion on a GM car, safest bet is a GM oil designed specifically for this. It's discontinued but still available through Amazon.
• If the compressor exploded and spewed it's guts through the system, then flushing is a must! If you don't know why the AC was removed, probably a good idea to flush and see if you get metal particulate. If so, you need a new accumulator and orifice tube at a minimum. Try to flush the heck out of the evaporator and condenser because the freon will just pull it all back to the compressor and explode the new one. A new condenser if fairly cheap, might be advisable insurance.

Pics
Gauges showing a good seal after 30 minutes


blower set up



Vent temp progress as I was adding freon







YEEEEESSSS!



sweatin it out



Low side pressure cycling

https://vimeo.com/356191363
To do yet:
Compressor is juuuust hitting hood support, so need to cut some of that away I cut a small relief in the hood framing, maybe something like a 3"x3" hole and will clean up the repair
Clean up compressor wiring
Wire max AC setting to cooling fan

Very happy with what I learned along the way, how it turned out so far, and looking forward to driving it whenever.

Pwnage1337

This is an awesome ******* post.

Gonna use this when I get the AC setup on my car.

Thanks!!!

Bad Karma

I don't suppose you kept a part number for the orifice tube you use?

Steve85

Welcome! It's long but I wanted it to be helpful!


I don't have the part# on the tube since it was already in there but these things are pretty standard across manufacturers. You can google "blue orifice tube" and options at Advance / AutoZone and others will come up.