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tkman55, Mechanic
Category: Medium and Heavy Trucks
Satisfied Customers: 139
Experience:  Diesel Truck Mechanic for over 34 years. Specialize in Thermo King and Carrier Transicold refrigerated units
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A/c 07 International 8600 evaporator inlet temperature 45

Customer Question

a/c 07 International 8600 evaporator inlet temperature 45 outlet 120 superheat. Where should I look for a blockage or is it something else?
Submitted: 2 years ago.
Category: Medium and Heavy Trucks
Expert:  tkman55 replied 2 years ago.
ok Here is how I check an AC before getting the tools out
turn it on low fan and lowest setting on cool I look to see if the clutch is engaged and how long it is staying engaged
I look at the reciver drier site glass to see if I have clear liquid flowing or bubbles I touch the suction line and the discharge line to see if one is cold and the other hot
I then go and check the air coming out of the vents if cold air is sensed ok but if hot air is coming from the vent then I most likely have a bad mix valve or heater valve that is keeping the heater on
the temps you gave indicate that the system is cooling your problem has got to be inside in the evap/heater section if there is a way to shut off coolant flow to the heater core do so and recheck to see if it is cooling then you need to locate the heater valve and see if it is closeing
Expert:  tkman55 replied 2 years ago.
paste and download the Diagnostic manual for HVAC on your unit hopefully it will be of help
your unit has motorized door to change it from heat to cool
Expert:  tkman55 replied 2 years ago.
Checking to see if you got your problem sorted out. Remember if you don't rate me then I will not get reimbursed for my time and effort
Customer: replied 2 years ago.
No replaced orifice. Reclaim and recharge to be sure right amount in ac system.
was 45 inlet and 87 outlet know. But it has no heater valve and vent door closed. I know the temp should be lower and almost the same.
Expert:  tkman55 replied 2 years ago.
were you able to download the troubleshooting manual for this truck?
there is a section on inlet and outlet temps via the thermistors and what to look for if the range is out 87 is high maybe you need to test the door actuator to insure it is closing the heat door or fresh air door tightly the instructions are in the manual
Expert:  tkman55 replied 2 years ago.
checking on your progress was the manual of any help to you? do you need more info?
remember to rate me when you are thru
Expert:  tkman55 replied 2 years ago.
rechecking on your progress?
Customer: replied 2 years ago.
Sorry out with food poisoning.
Well the temp as I was going to tell you gets up to 200+ and when I unplug the thermistor for outlet it still reads in the 200. I believe it is a short. Thanks for the diagram! Could this Be caused by the body controller? I also have the engine Fan will not shut off. I fixed a bunch of shorts a little over a year ago. Bare wires control box little black was full of water and all rusted. I never could get the fan clutch to shut down. I guess the body controller is working because it shuts down the system because it sees a super heat condition. Do you have a wiring diagram and is their a transducer in a thermister system, I am unaware of?
Expert:  tkman55 replied 2 years ago.
here is the manual for your unit ac thermistor s work on ohms so ground wire or an open wire will change the reading there are only 2 temp thermistors in your unit
Customer: replied 2 years ago.
I need the wire schematic please if you have it. Thanks
Expert:  tkman55 replied 2 years ago.
Took me a while to find it here you go
Expert:  tkman55 replied 2 years ago.
if you are still reading 200-240F then your thermistor is shorted or your wiring is shorted.
disconnect the thermistor and recheck your temp should read around 0F indicating an open circuit and telling you that you don't have a shorted harness. replace the thermistor if the reading doesn't change then your harness is shorted
Thermistor Diagnostics
Shorted Thermistor Diagnostics
For diagnostic purposes, the body controller monitors the voltage levels across the inlet thermistor and the
outlet thermistor to determine if either thermistor circuit is open or shorted to ground (or zero volt reference).
Because the body controller does not detect the full range of voltage values it cannot directly detect an open or
shorted circuit. If the body controller reads a thermistor voltage value at the low end of its range of possible
values it assumes that the thermistor circuit is shorted to ground, because this value (which corresponds to
240°F) does not reßect a normal reading.
The body controller will set a fault indicating that the particular thermistor is shorted to ground. In addition,
the body controller will inhibit A/C compressor operation until the short is no longer detected, AND at least 8
seconds have elapsed since the A/C compressor clutch was de-energized.
Customer: replied 2 years ago.
I still am reading over 200 and i disconnected the wires all have a perfect signal. We had originally
repaired and replace both thermistors and wire connectors. If you unplug the thermistor it reads the same it dose not go to 0. I tried to get your info from dropbox but it always says error page. I fit to be tied over this one.
Expert:  tkman55 replied 2 years ago.
safe to say that the wiring is shorted but it will be Tuesday before I can put the AC diagnostic manual back in my dropbox for you

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