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George H.
George H., ASE Certified Technician
Category: Car
Satisfied Customers: 18817
Experience:  ASE Master Tech 15+ yrs, AAS Automotive Technology, Factory trained Asian specialist
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2001 hyundai xg300: green wire going to the evaporator..12 volts

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I have a 2001 hyundai xg300, when i punch the ac on switch the compressor does not come on. the ac on switch has a green wire going to the evaporator thermostatic switch.
the thermostatic switch has a light blue wire coming out of it going to the triple switch, when i apply 12 volts to the light blue wire the compressor comes on and works normal. if i apply 12 volts to the light green wire that comes form the ac on off switch the compressor does not come on. should there be 12 volts on the light green wire coming from the ac on off switch or should there be a 5 volt referance output. and how do you test the thermostatic switch?

Hello I will help you with your question,


It is common for the thermoswitch to fail It is unfortunate that the evaporator will have to be removed to replace this switch.


This is a transistor that the base is pulled low by the temperature of the evaporator core and that allows the PCM input to be connected to the 12 volts of the control head. This is a very weak signal so it can be pulled down by a faulty thermoswitch. I have had success cutting and splicing a new head on the thermoswitch so you would not have to replace the thermister just install a new connector/head


The thermister is about $75 at Hyundai and there is a TSB about relocating the sensing bulb if you do replace the entire switch


Here is the wiring diagram for this part of the system, you have done the testing that is possible



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