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Old May 14th, 2019, 9:26 PM
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Default Hvac systems

03 tahoe z71 .
I have checked everything threw out my whole ac system have found out im not getting power to my ac clutch relay whats my next step ? Where are the wires that run to it ?
Old May 15th, 2019, 12:29 AM
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the ac relay is turned on by the pcm….the pcm provides grd on relay pin 85. this closes the relay to engage the compressor clutch. if you jumper grd to the wire or pin on 85 and the compressor clutch engages...the pcm is inhibiting ac operation

there is a low pressure switch that is an input to the pcm...if the switch is open. the pcm won't turn on the relay. have you checked the switch, is the system charged with refrigerant?
Old May 15th, 2019, 8:53 AM
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Originally Posted by Colden Moore
threw out my whole ac system
I'm assuming that the system is not really in the trash !!!


OK, like posted previously: get a real set of R134a service gauges and read the static pressure - if any - of your system. Could be that the systems are simply doing their job of protecting the system.

Do NOT "add refrigerant" blindly, and NEVER add any sealers or refrigerant containing sealers !!!
Old May 19th, 2019, 5:47 AM
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Originally Posted by tech2
the ac relay is turned on by the pcm….the pcm provides grd on relay pin 85. this closes the relay to engage the compressor clutch. if you jumper grd to the wire or pin on 85 and the compressor clutch engages...the pcm is inhibiting ac operation

there is a low pressure switch that is an input to the pcm...if the switch is open. the pcm won't turn on the relay. have you checked the switch, is the system charged with refrigerant?
Where is the low pressure switch located? And yes its charged
Old May 22nd, 2019, 3:37 PM
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Originally Posted by Colden Moore
Where is the low pressure switch located? And yes its charged

on the low side....usually around the ac accumulator (the soda can looking thing)




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