A/C & Cooling Fan Connections
05-02-2007, 02:36 PM
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A/C & Cooling Fan Connections Hello,
I have read the "sticky" on the fan wiring diagrams. This was very helpful. I also posted a question, but I am not sure anyone will see it since the post is so old.
My question is, what is recommended for aftermarket A/C systems like Vintage air? Also, what is the difference in the PCM between Low and High? Are the two set points in the computer? Are both programmable?
If I have the PCM controlling the fans as diagramed, should I tie the A/C into the PCM or just start the fan directly? Should I start one fan or both fans?
What does Red 17 and Red 43 on the PCM do?
Thanks.
Phillip
I have read the "sticky" on the fan wiring diagrams. This was very helpful. I also posted a question, but I am not sure anyone will see it since the post is so old.
My question is, what is recommended for aftermarket A/C systems like Vintage air? Also, what is the difference in the PCM between Low and High? Are the two set points in the computer? Are both programmable?
If I have the PCM controlling the fans as diagramed, should I tie the A/C into the PCM or just start the fan directly? Should I start one fan or both fans?
What does Red 17 and Red 43 on the PCM do?
Thanks.
Phillip
05-02-2007, 05:04 PM
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I believe Red 17 asks the PCM to turn on the AC compressor, and Red 43 turns on the relay that actually powers the AC compressor clutch. The PCM monitors AC pressure, throttle position, and RPM to enable and disable the AC clutch, and it tweaks the spark timing momentarily when enabling and disabling the AC clutch. I think the PCM also controls the fans based on AC pressure (if AC is requested via Red 17), but I can't find any reference to that at the moment (isn't jumping out at me in HPTuners).