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A/C Expansion Valve - Where is it and how do you change it??

Discussion in '80-Series Tech' started by Nstig8r, Apr 25, 2009.

  1. Nstig8r

    Nstig8r New Member

    As the title says, I have diagnosed it as being bad, but cannot find where this is or how difficult it is to change. Is there a writup anywhere?? I have been unsuccessful searching for one...

    Does the evaporator have to come out of the car and if so, how big of a job is it??

  2. dragr1

    dragr1 New Member

    Auburn, AL
    I can't help you Tom, but I can reply and bump you back to the top!:D
  3. john_eckels

    john_eckels SILVER Star

    Columbus, OH
    I think it's in the dash with the evaporator. For the cooling unit, the FSM says to remove the glove box. I did a quick search of the FSM and did not see any pictures showing the location of the expansion valve. I think I remember reading a thread that says you need to tear the dash apart in order to get to it.
    Last edited: Apr 25, 2009
  4. Kalawang

    Kalawang New Member

    Starting at the compressor, touch the pipe and follow the cold. The expansion valve, if it is the culprit, will be between the hot and the cold. Of course, the air con has to be running for this to work.

    I'd like to give you more explicit directions but they put those things in different places, some of them very hard to get to. If it were on a table where you could get at all the nuts and bolts it would be easy. Unfortunately it's normally tucked up and out of the way making it difficult to even reach. I hope you are patient, flexible and capable of working in very odd and uncomfortable positions.

  5. 1972FJ55

    1972FJ55 New Member

    Tucson, AZ
    Is the system going into a vaccuum? That's the standard to look for when diagnosing a bad expansion valve. I think it's using an expansion block, which is attached to the evaporator. That mean extricating it from the dash, to replace it. Alas, since I don't have an 80, I don't know what's involved in taking the case out. I'd replace the drier at the same time, since it could be the cause of a malfunctioning expansion block. At least the parts are reasonable. I can get more information on Monday, if you need it.
    Good luck,

    Attached Files:

  6. Nstig8r

    Nstig8r New Member

    My A/C would work intermittendly, probably 90% of the time, so I thought my 'Cruiser was just low on 134a. We dumped the system, and after about an hour of vacuuming, we got it down to almost 24lb's of vacuum.

    Now, the sticker on the radiator support says 2.5lbs of 134a (40 oz), so we added three full 12oz cans. When we got halfway through the fourth can, the low side was still in vacuum, and the high side was almost 150. Could not figure out why both sides were still low, so I looked on here and found someone posting from a factory manual that it takes 60oz, +/- 2.

    So we finished the fourth can and added the fifth. Once we got to closer to 60oz, the low side was still low (almost vacuum), and the high side spiked, and spiked HIGH. Enough to where we were standing back waiting for a line to blow (almost 450 on the high side). Only thing that can do that is a bad expansion valve...

    So, I guess I was hoping someone had a writeup about the replacement online...
  7. jjfj80

    jjfj80 SILVER Star

    Oklahoma City
    In the FSM for a "91 FJ80, the drawings/instructions are in pages
    AC 26 through AC29. I can't figger out how to link the drawings,
    but it appears you just have to remove the glove box to get to the expansion valve.

  8. TX Cruiser

    TX Cruiser New Member

    Austin, TX
    Try back flushing it before you change it. Remove the lines at the fire wall and flush from the low side back to the high. In laymans terms, that would be from where the fat hose was connected to through the evap and back out where the skinny hose was connected. Use your finger to cover the hole and release every second or so when the pressure builds up. You will need an air compressor and some solvent to do this. You will also want a rag or towel b/c the solvent burns when it gets in your eyes.

    Let me go check my 91, but I'm pretty sure the expansion valve block is right at the firewall where the lines connect.
  9. TX Cruiser

    TX Cruiser New Member

    Austin, TX
    What year is your cruiser? The '91 FJ80 is max 2.09lbs of R12. That's 33.44 oz., cans are 12 ounces, most of the time. When using 134 in a R12 system, the rule of thumb is 80% of the rec for R12 or roughly 27 oz. That guy put way too much freon in, and I'd be a little hesitant to take it back to him, he was about to blow something up. Actually, I wouldn't take it back, period. He's probably right about the expansion valve though.

    The '94 is max 1.98lbs of 134. It came from the factory with 134, and the difference in capacity is probably due to the relocation of the dryer. The systems are nearly identical otherwise. The expansion valve is in the same location on both the FJ and the FZJ.

    I'm just going by what I see when looking under the hood in the drive way. The freon charge is the real deal, no lies, Nippondenso factory sticker, and I do a/c work.

    It looks as if you can separate the evaporator from the truck without having to remove the dash, but it (evap) has to come out in order to change the valve. Try back flushing first.
  10. cruiserdan

    cruiserdan SupportingVendor Emeritus Moderator Supporting Vendor

    The evaporator assembly has to come out of the truck and then it gets split in half to get to the expansion valve.

    The glove box and lower brace have to come out. The sytem needs to be evacuated and the buklhead connections at the outside of the firewall need to be disconnected. The evaporator then gets unbolted and the wiring disconnected and it comes out toward the passenger seat.

    Do be careful because a new evaporator assembly is about 1,400 bucks..........:eek:
  11. Scamper

    Scamper New Member

    Somewhere in NJ
    Like Dan said...the expansion valve is in the evap assembly. I belive Toyota refers to this as a "cooling box". The entire cooling box is removed from behind the glove box after disconnecting the high and low side at the firewall.

    The expansion valve itself is attached to the evaporator in the cooling box. Just held on by one or two bolts IIRC. The cooling box has to be opened, which is done by removing a few screws and clips. Pretty easy to do, though do be careful. A good time to clean out the evaporator too since a bunch of debris is often accumulated in there.

    But I noticed that you said you were only able to evacuate to -24 inches. The system should be evacuated easily to at least 30 inches unless you have a leak in the system somewhere (or your vacuum pump is no good). And like Tx said, that AC guy put WAY too much refrigerant in the system; my '97 takes only two and a half of those 12 oz. cans to fill (840 gm). If he put 4 cans in there, he may have damaged the compressor.

  12. khoopes

    khoopes Regular Member

    I have been having intermittent cooling probems on my 93' FZJ80. It was inop whem I bought it with a high side hose blown. I fixed the hose and vacuumed the system down. Refilled it with R12. I did not have an adapter for the little fitting on the high side but filled it till I was running about 32 lbs on the low side at about 1800rpm.

    Since then it works intermittently, i.e, it cools a little all the time but sometimes it cools really well. When it is not working right the Duct temp is about 70 degrees, and then for no apparent reason sometimes it will begin blowing about 40 degrees and keep us comfy.

    I have had some fuse block problems, does anyone know of any electrical components that can keep the system from properly cooling? The A/C compressor runs all the time whether cooling poorly or good. I have suspected the expension valve for a few weeks but the replacfment procedure is daunting when you consider I have to lose my $70 worth of R12 I just put in.. :-(

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