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Thread: Thermostat valve impact on AC

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    Default Thermostat valve impact on AC

    Car: Toyota Corolla 1984 (AE80)
    Engine : 2A
    Status: Engine recently overhauled, completely.

    I am stuck with a problem with AC of my car. T-stat valve was installed, fan was auto, and direct when AC is ON. Temp meter is after warming up stays at middle, and t-stat valve is not stuck. Single channel (aka single naali) radiator installed. Service the AC system, installed new cooling coil, drier, expansion valve, condenser, and all lines. Compressor was re-used.

    Cooling remains good during night, but during day it is barely noticeable. Tweaked by AC technician several times, but no result. In the end it was concluded by him that problem is due to single channel radiator. for checking this statement, he suggested to remove t-stat valve. After removal, cooling significantly improved during day.

    He is insisting to not to install t-stat valve during summers, which I don't want to do. Can replacing radiator be a solution?
    Pls suggest, as I don't want to spend money just for trying. Urgent help needed as I don't like driving without t-stat valve removed.


    Click here for SOLUTION

    Prepare for the worst, Hope for the best.

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    The hot/cold knob on the dashboard controls a valve. When you turn the knob to hot, it shuts off the valve which prevents hot coolant from reaching the heater core. If the valve is bad, hot coolant will keep flowing through the heater core, which warms up the air mix box. So that takes away some of the cooling efficiency. The second issue is with the air mix box itself, the different modes which direct air to the feet, windscreen etc works by redirecting the air using different doors in the air mix box. To create a better seal, foam backing is used on the doors. Over time, the foam can disintegrate and the doors cannot create a proper seal, which is why if you set the air mode to one vent, some air still escapes from other vents. So in effect , cold air from the evaporator mixes with hot air. The solution is to open the box and replace the foam so the doors create a better seal (been there, done that). In many cases that requires removal of the entire dashboard. To diagnose this issue, remove the valve and check if it is seals shut when closed.

    I suspect your problem is either a bad valve, an under-performing compressor, or a condensor fan problem. The thermostat valve is unrelated to the issue you are facing. If the radiator is not up to the task, it can cause your compressor to overheat and trip more often, so that is worth looking into as well.
    Never argue with an idiot, they drag you down to their level and beat you with experience.

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    Quote Originally Posted by whiteangel View Post
    The hot/cold knob on the dashboard controls a valve. When you turn the knob to hot, it shuts off the valve which prevents hot coolant from reaching the heater core. If the valve is bad, hot coolant will keep flowing through the heater core, which warms up the air mix box. So that takes away some of the cooling efficiency. The second issue is with the air mix box itself, the different modes which direct air to the feet, windscreen etc works by redirecting the air using different doors in the air mix box. To create a better seal, foam backing is used on the doors. Over time, the foam can disintegrate and the doors cannot create a proper seal, which is why if you set the air mode to one vent, some air still escapes from other vents. So in effect , cold air from the evaporator mixes with hot air. The solution is to open the box and replace the foam so the doors create a better seal (been there, done that). In many cases that requires removal of the entire dashboard. To diagnose this issue, remove the valve and check if it is seals shut when closed.

    I suspect your problem is either a bad valve, an under-performing compressor, or a condensor fan problem. The thermostat valve is unrelated to the issue you are facing. If the radiator is not up to the task, it can cause your compressor to overheat and trip more often, so that is worth looking into as well.
    Sorry for not mentioning that heater core is disconnected, foaming within heater core box is re-done. Flaps are working perfectly.
    Prepare for the worst, Hope for the best.

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    Also do a check of the fresh air lever. Problem could be caused by fresh air mixing with cold air coming from evaporator
    Never argue with an idiot, they drag you down to their level and beat you with experience.

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    Your condenser is in front of the radiator - removing the thermostat valve would have no effect in cooling down the condenser at all which is the actual place of heat rejection in the A/C

    are your fans working in good form? shrouds sealed to radiator, fan rpm normal?

    What condenser type are you using and what refrigerant are you using? The old 84 corolla has a very small evaporator coil and condenser and requires R12 unless you have modified it to fit a 100 series coil in it.
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    Quote Originally Posted by whiteangel View Post
    Also do a check of the fresh air lever. Problem could be caused by fresh air mixing with cold air coming from evaporator
    No leaks from fresh air duct
    Prepare for the worst, Hope for the best.

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    Quote Originally Posted by Xulfiqar View Post
    Your condenser is in front of the radiator - removing the thermostat valve would have no effect in cooling down the condenser at all which is the actual place of heat rejection in the A/C

    are your fans working in good form? shrouds sealed to radiator, fan rpm normal?

    What condenser type are you using and what refrigerant are you using? The old 84 corolla has a very small evaporator coil and condenser and requires R12 unless you have modified it to fit a 100 series coil in it.
    You are right that t-stat will not cool down condenser. But AC wala said "with t-stat, compressor is heating up too much"

    Fans are speedy and blade edges are fine, shrouds sealed, extra foam packing also done between radiator and compressor to avoid air escapes.

    Yes u r right the system has been modified to 134 system. Condenser is not multi flow, as per AC wala the space for condenser cannot accommodate multi flow thing.
    Prepare for the worst, Hope for the best.

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    how about stacking two small condensers or a refrigerated dryer if you are adamant to use R134 in your system, With R134 - you only have to use 80% of the weight charge of R12 otherwise the system fails to work.

    It might be that your system is overloading and the A/C technician does not know this. He is trying to mask the heat load and not solving the problem.

    Use R12 in the system and retest - also use a genuine expansion valve.
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    Quote Originally Posted by Xulfiqar View Post
    how about stacking two small condensers or a refrigerated dryer if you are adamant to use R134 in your system, With R134 - you only have to use 80% of the weight charge of R12 otherwise the system fails to work.

    It might be that your system is overloading and the A/C technician does not know this. He is trying to mask the heat load and not solving the problem.

    Use R12 in the system and retest - also use a genuine expansion valve.
    Xulfiqar bhai, pls explain system overloading. And getting R12 is an issue itself.
    Prepare for the worst, Hope for the best.

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    System overloading = system incapable of rejecting or absorbing heat at the required rate, This is 80% of cases which are running R12 hardware with R134 gas - R134 systems have very large area condensers and evaporators because R134 is a very stubborn gas.

    R12 could freeze you with even smallish hardware like your corolla has.
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    Xulfiqar, thank for your reply and all details.
    Condenser presently in use is almost of width of front grill. So what's the conclusion? Should I move to R12? or should I change the radiator to dual channel one?
    Went to too many AC walas, and they say they cant source R12.
    Prepare for the worst, Hope for the best.

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    R12 can be sourced easily if you know where to look. What are the run pressures in your system?
    ZRS - Zulfiqar Racing Systems ..... - professionals at work - at crackwheels.com

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    Quote Originally Posted by Xulfiqar View Post
    R12 can be sourced easily if you know where to look. What are the run pressures in your system?
    wont it need replacing compressor as well? at present compressor is sanden (507 if I remember rightly). For pressures, I didn't looked into them while he was filling. Don't have the guage as well.
    Prepare for the worst, Hope for the best.

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    @Xulfiqar,
    Update:
    Finally after reading your replies on other posts as well, made few changes.
    1- Replaced both fans with speedy ones. Blade edges sharp and not de-shaped.
    2- Made sure that condenser and radiator take maximum air, sealing spaces in between and other places with foam.
    3- Changed radiator to two-channel one.


    Results:
    Cooling is improved, infact very improved in day times. It was barely noticeable in day time, when these changes were not done. But it is comfortable now.


    Thank you Xulfiqar bhai for your valuable suggestions and advices. These advices and suggestions doesn't gets digested by our Ustaad jees, but pays off if done rightly.


    Now, as I still want to install AUTO RADIATOR FAN + THERMOSTAT, and so I did. Cooling was same.
    But, few other problems showed up.

    1- At cold engine, RPMs stable.
    2- Once reaching its required temperature, Idle goes high up to 1.5k RPMs. Brake servo loose brake assist and gets hard.
    3- Engine changes its sound, like running under load.
    4- Car pickup significantly decreases.


    Pls suggest what to do.
    Prepare for the worst, Hope for the best.

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    adjust the carby when the engine is at normal temperature.

    Thankyou for your appreciation.
    ZRS - Zulfiqar Racing Systems ..... - professionals at work - at crackwheels.com

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    Salam , zulfiqar bhai, required your expert opinion about my Honda city 2008 AC..

    month ago i've cleaned them everything like AC servicing and condenser was changed and got new one, the colling was fine even at 42c day time.. but all of a sudden i felt that fro the last week colling of my city isnt that good as it use to be month ago..AC gas was toped up when service done..i asked some one they said clean your radiator and than see if it would help..

    before i can do anything i need to ask expert ppl here.
    whatw would be the reason why..

    Thanks

    waiting for your reply

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