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Inadequate cooling in old Toyota Sienna

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    Inadequate cooling in old Toyota Sienna

    Amateur owner questions.
    Inadequate cooling in old 2001 Toyota Sienna. Manual AC. Front and rear AC with separate expansion valves and evaporators.

    Bought 1 yr ago. Subjectively good AC performance in 85 degree weather 1 yr ago. Barely adequate AC 3 months ago in 100 deg weather. July 2018 inadequate cooling in 100 deg weather. Barely cool in 75 deg weather.

    Checked pressures 2 days ago.
    Ambient temp about 90 deg F.
    Humidity not known.

    AC vent temp measured using digital meat thermometer in degrees F. Air flow to vents normal at dash and rear AC. Temps at rear AC not better than dash.
    Temp of upper and lower condenser lines measured with IR thermometer in degrees F. Do not know if this is accurate. Do not have AC temp probe.
    Used HFT manifold gauge.

    Compressor does not cycle when testing. Clutch engages when AC is on and does not disengage until manually turned off when tested at 75-95 deg F.

    Has hot water valve. Visually checked valve under hood. Valve moves from hot to cold position when hot-cold knob is turned to cold.
    Hot-cold knob at dash to hot makes vent air hot. Knob to cold makes air colder. Do not know if water valve actually shuts hot water off. Do not know how to test doors of air ducts but there is a thump when moving knob from full cold-hot-cold.

    R134 Pressures:
    Engine off
    LOW 80 psi
    HIGH 80 psi
    AC vent temp 94F

    Engine on AC on
    Engine idle 700 rpm
    LOW 30 psi
    HIGH 135
    AC vent temp 68

    Engine 1500 rpm AC on
    LOW 25
    HIGH 145
    AC vent temp 68

    Added R134 without sealant for 30 seconds. Did not weigh can. Probably less than half 12 oz can dispensed.
    Recheck pressures.

    Engine 1500 rpm AC on
    LOW 35 psi
    HIGH 190
    AC vent temp 76F. Yes, vent air felt warmer.
    Misting condenser did not improve vent temp but did not recheck pressures.

    2 days later. Ambient temp 77 deg rel humidity 65%.
    Checked temp of condenser upper and lower lines with IR thermometer. Unknown if this is accurate. Did not recheck pressures.

    Engine at Idle 700rpm.

    Upper 137deg F -145 deg F at first.
    Upper 137-140

    Lower 117-122 at first
    Lower 130
    The difference seems low to me if measurements are reasonably accurate. Difference is less if AC is run longer.

    I felt refrigerant was slightly low at first but adding some did not help performance.
    Vent air seems to get hotter if I test for 30 minutes or longer. Driving the car to get airflow helps minimally.

    Seems compresor is making pressure and refrigerant level is enough to get better cooling than I now have.
    Temp difference across condenser seems low if readings are reasonably accurate. Do not know how to check for restriction. But r134 pressures are not high so maybe is not restriction. Condenser does not appear dirtier than my other cars but have not tried to clean it beyond hosing it to mist it.

    I do not know how to check hot water valve or evaporator.
    I do not know how to check expansion valves or evaporators. Has front and rear expansion valves and front and rear evaporators according to parts web site. Both front and rear vent air are equally hot so not so likely to be evaporator or expansion valves problem as the front and rear are separate.

    In the end, maybe condenser is the problem.

    What to do next?

    Welcome jack4,
    A/C isn't DIY or "amature" friends - web BS and all this vehicle would be a high end one to deal with dual A/C more than doubles the troubles. Just static pressure you listed with engine off should suggest system is close to empty.

    This quote by you >"R134 Pressures:
    Engine off
    LOW 80 psi
    HIGH 80 psi
    AC vent temp 94F"<

    It really can't be that if general air temp around the engine and vehicle was warmer than 80F pressures have to be higher just sitting there. All credibility of your equipment the thermos now in jeopardy of being wrong. A/C doesn't tolerate guessing and being wrong.

    Absolutely no offense or discouragement to you but a suggestion that will save you endless expense if you insist on fixing A/C to work as intended and have a chance to last.

    Just find the exact right shop, certified to deal with A/C and also familiar with the exact vehicle. In one year you are not going to know with a system declining in performance and at the age now what happened all along the equipment alone would outprice this vehicle new. Experience a must and knowing how to use that equipment out of control time for just that,
    Last edited by Tom Greenleaf; 07-30-2018, 05:25 AM. Reason: Fix Typo
    MetroWest, Boston


      I would either take it to a good shop or get ready to spend some money! You will need a good vacuum pump ($100-150), a leak detector ($50 -$75) and an accurate scale ($50 - $100) to go further on your own. You may be able to rent or borrow these items from Auto Zone.
      Tight Lines!


        ? Where did you find those prices? Auto Zone rentals AYOR in my opinion for A/C - uggh! They aren't allowed to rent in some places at all and do not rent leak detectors that I know of would want to be real sure it's found and proven fixed. BTW - my electronic mid cost leak detector cost about $350 quite some time ago still works fine just one tool in the arsenal of leak finding. They don't work well or can trust them at all if too windy or will pick up wrong signals from other things in areas like if any cleaners or sprays were recently used.

        Trusting your equipment is imperative plus knowing when to doubt it,
        MetroWest, Boston


          AMAZON. My equipment works just fine. We have no "off season"; Air Conditioning is used year round here. What does AYOR mean?
          Tight Lines!


          • Tom Greenleaf
            Tom Greenleaf commented
            Editing a comment
            AYOR = At Your Own Risk.