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93 Toyota Pickup Recharge Challenge (converted from R12 to R134A)

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  • 93 Toyota Pickup Recharge Challenge (converted from R12 to R134A)

    Hi forum friends,
    New user and my first post. Thanks in advance for your help on this project...
    93 Toyota Pickup 2WD 22RE engine. It was converted to R-134A maybe 10 years ago and has worked well ever since, until recently when the AC belt started squealing and smoking, so I pulled over and cut it off (glad it's a separate belt so I could keep driving!). I figured the compressor seized up since I could not turn the pulley, so I bought a new kit (Four Seasons, complete with a new receiver/dryer, TXV, and o-rings, and PAG 46 oil). I even bought a separate OEM TXV valve since I read a bunch of negative reviews about the Four Seasons TXV).
    Turns out the compressor was not seized up!.. I could still turn the center part/clutch but the outer pulley was what locked up, I'm guessing it was a bearing? Anyway I'd already dismantled the system when I realized this, so just FYI.
    I got an AC flush kit, manifold gauge set, and vacuum pump/oil from AutoZone (had to get special flush solvent from Napa Auto since AutoZone didn't have it). Got a couple 12 oz. cans of DuPont 134a on Amazon as well as some UV dye.
    When dismantling, the old compressor SEEMED to have hardly any oil in it (darker, assume it was still original mineral oil?, FYI). All cleaned out nice and it sat for a few days so I think any solvent should have evaporated. New compressor, R/D, TXV and even a new OEM thermistor since the old one didn't show good ohm readings per the giant 2-book-size Toyota repair manual. I seriously believe I got the last thermistor ($9) in the COUNTRY! Anyway...
    Per conversion specs 7 oz. PAG 46 oil and ready with 22 oz. of R134A...
    I draw a good vacuum (1 hour) and it holds overnight so I'm happy and go to charge the system.
    I took good notes because this was my SECOND attempt to charge the system. (before I replaced the TXV and thermistor, also cleaned the evaporator which was full of pine needles).
    So here's what happens when I go to charge the system. (gauges= L: -29, H:0). Can attached, yellow hose primed/purged and ready.
    I start the engine, turn on AC inside and blowers at second to highest force, and open low side on manifold gauge.
    L-side jumps to 70 while H-side stays at 0.
    After 10 minutes, clutch engages, L:55, H:50. Clutch remains engaged through steps below. There was no cycling on/off of the clutch.
    After 20 minutes, L:57, H:70
    After 30 minutes, L:72, H:90
    After 40 minutes, L:75, H:100
    After 50 minutes, L:76, H:115
    After 60 minutes, L:76, H:115
    I'm not sure how long an AC recharge is supposed to take but I figure it should be much faster than one hour?!
    Note that during this one hour "recharge" the can is on a scale and apparently the system only took about 6 oz. of R134a in that entire time.
    I shook can regularly and it felt cold.
    So after the hour with head-scratching results I decided to call it quits.
    With engine still running I close the LOW side on manifold (H has been closed the entire time), the low side drops instantly to L:0 (strange?), high still H:115
    then when I shut off the engine, both low/high sides quickly stabilize at about 65
    What the heck do I do now?
    Thanks so much for your expertise and advice!

  • #2
    Sounds like you are having trouble getting the 134a to flow into the system, either your quick connect isn't connecting properly or someone left the valve cores in the R12 ports when the put the 134a retrofit adaptors on.
    I hate to have to tell you, and I'm sure you realized it by now, but rather than throw parts at it, had you first checked for the exact problem, the hub bearing, you could have replace just that and not opened the system!


    • MMC
      MMC commented
      Editing a comment
      How do I check the valve cores?... they hold pressure and if I press the "shrader valve" air enters (if under vacuum) or air (or R134a) comes out if evacuating, so thinking the valve cores should still be fine. Is there some other test for them?
      Is there a test for the manifold gauge set? Similarly when it's connected obviously I can draw a vacuum so air can go OUT of the valve.
      It took SOME R134a into the system so "air" can go in at least slowly. I heard something about a "pressure test" (opposite of vacuum test?) perhaps I should used compressed air to pressurize the system to see if it holds? Hmmm. Thanks.

  • #3
    1st don't comment on a post, use the reply box below it. If you comment, it doesn't show as a new post on the thread, so unless I look back I will not see that you replied. If you use the reply, the title gets highlighted and I know there is new material.
    NEVER use compressed air to test, it has moisture and oil that can cause problems, dry nitrogen is used for pressure testing in A/C work.
    No real good way to check for double valve cores but to remove them and look, Sometimes a double core will pass a little as the stem from the outer core might reach the inner enough to crack it off it seat.
    Because your low side stays high until you close the hand wheel on the manifold, then drops to vacuum, that tells me the restriction is between the manifold and the low (suction) line on the vehicle. That leave the hoses from the manifold, their connectors and the service ports on the system, to be the only places that would give the symptoms you describe.