InternetRoadkill

I'm trying to get my A/C working again on my 88 4Runner. Long story short, Many years ago I had converted the system to 134A (oil change, purge, recharge, new TVX, etc.) and it sorta worked. But it never cooled very well and leaked. So I'm removing the R134 and PAG oil and using an R12 substitute this time around. Everything is going well except I need to replace the schrader valve cores inside the charging ports. The new valve cores fit just fine in the high-side port. But attempting to fit a new core in the low-side doesn't fit. It turns about a 1/2 a thread and won't go any further. Unfortunately, the original valve core was missing from the low-side so I can't compare them. I did try the old high-side core in the low-side and it doesn't fit either. I don't see anything wrong with the threads. It seems the low-side port uses a different size/thread valve core from the high side. Has anyone run into this before?

aztoyman

It should be the same. Is it in the original port or do you have adapters on the original ports? I've had adapters that required you to remove the original Schrader and the adapter had it's own, And I had adapters that used the Schrader in both the adapter and the old port.

I've even used tire valves in a pinch. Since the tire valves are the same, maybe find a tap that fits a tire stem. Once you know it's the correct tap try to clean up the threads on your compressor port. Or use a tire valve AS the thread cleanup tool.

I wonder why your R134 conversion didn't work well. I converted a bunch of the 80's trucks and they cool great. I found mine cooled the best with LESS refrigerant than the conversion called for. I just did a1990 pickup last summer. I even used the original evap, condenser and compressor. Cooled great. New TXV, drier, O-rings, flush and oil. I used Ester100 oil though. The oil type shouldn't make a difference on the cooling. Unless too much oil in the system.

Good luck with it. Let us know what you find out.

InternetRoadkill

I had the adapters on there to allow 134A charging. I'm thinking the adapter may have distorted the port since the ports are just cast aluminum. I'm going to pick up a 4-way valve core tool to chase the threads tomorrow. If all else fails, I can just put the adapters back on. I was able to verify that the valve cores should be the same on both ports. If anyone cares the Toyota part number for the cores is 88374-20020. Hopefully, the seat in the port is not damaged.

I tried adjusting the amount of 134A charge in the system to get better performance, but it was still no match for 90+ degree days in the sun. It tried to cool, but took forever. From what I've read it seems that 134A requires a larger condenser compared to R12 which degrades the performance when converting. Also R134 has a lower heat capacity than R12 which doesn't help.

I've pulled the entire AC system out of the truck for cleaning and inspection. The evaporator and condenser are going to get flushed and cleaned. They're in good shape. I already replaced the TXV when I did the previous conversion. I'll just wash the old oil out of it. I'll replace all the o-rings again and I'm making a new set of hoses maybe tomorrow. I'm still waiting for the crimp tool to arrive. I already got a new compressor since the old one seemed to be leaking as evidenced by the UV dye. Unfortunately, I discovered the clutch was toast. I had intended to re-use the clutch from the old compressor. But it looked pretty bad. So I had to order a new one. They are getting hard to find and they are ridiculously expensive now. Hopefully, it will get here early next week. I'm looking forward to having a functioning AC again.

aztoyman

I understand. I'm in AZ and I gotta have it too. I've been lucky. So far never HAD to upgrade the condenser. It would definitely help to have a more modern efficient one though. I'm building an 86 Xtra Cab right now. I'm probably going to put a universal condenser from Vintage Air on this one. I used one on a system I built for my 52 Ford pickup and it works well.

Sucks about your clutch. Good luck with it. I hope it's ice cold for you. Thanks for posting up what you found and the part numbers. Dead end threads suck.

InternetRoadkill

A quick follow up: I bought a 4-way valve core tool from WallyWorld and chased the threads on the service port. It seems the first 2 or 3 threads were damaged. After that, the valve core would start and get stuck after a couple of turns. A little extra push got it past the bad spot and it went in just fine after that. Standard valves cores fit the service valve. But I'm not sure if they are compatible with the refrigerant and oil, so I ordered some replacements from Toyota. They're a $1 each.

aztoyman

Thanks for following up. Helps others down the road to find an answer, not a dead end thread.

I completely forgot about the 4 way valve stem tools. I have two sizes sitting in my tool box.

No the tire Schrader valves are not 'supposed" to be used on A/C. I have though. All I had for a field fix. Never had to replace it. I thought you might be able to sacrifice some to fix your threads.

Sounds like you're on your way to A/C goodness.