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Old 08-20-2014, 09:22 PM
Tech II Tech II is offline
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Re: No power to AC Relay, need help!

Kind of need a scan tool to read PCM data, for diagnosis.....

Looking for three things:

One, check for an AC trouble code.....

Second is AC request from the control head......

Third is data from the pressure sensor......this will tell you if you have enough refrigerant in the system for the compressor to start.....

If you don't have access to a scan tool, then get a set of gauges to check pressure in the system....if too low, the PCM will not ground the clutch relay.....

Pressure in the system, on a cold vehicle, with the engine not running, should be close to ambient temp.......so if the air temp is 80 F, pressure should be around 80 psi.......if pressure is 40 psi or less, the PCM will not ground the relay.....
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