AC Compressor Wire Gauge

[RMBaiada]

I have installed a new AC system in my 1974, including a Sanden AC compressor/clutch and a 12" x 14" parallel flow condenser and had a few questions.

 

1. What gauge wire should I run to from the AC compressor/clutch to the on-off switch in the console? The lead from the AC compressor/clutch looks to be 14 gauge.

2. Where is the best place to tap off power?

3. What amp fuse is needed?

4. Should I add an inline fuse or rely on the fuse box?

 

Michael

[Mike Self]

I'm a great believer in "the wire can't be too large"--within reason, of course.  The thicker the wire, the less resistance.  And the price of 12 gauge vs 14 gauge wire is negligible.  

 

You need a 16 amp fuse just to be on the safe side, and if you're installing a Behr unit, it's wired so that you can't turn on the heater blower at the same time as the A/C is on.  I believe that wiring a Behr unit instructs you to wire it through the heater wiring (you should find a Behr diagram somewhere here on the FAQ).

 

If it's Frigiking, it's not wired that way, but taking a tap off the 16 amp fuse that serves the heater would work OK; most Frigikings I've seen are wired thusly.  It's only live when the ignition is on (which you want)--and I've had both my heater blower and A/C on at the same time, and it didn't blow a fuse, so the circuit can apparently handle both.  

 

Clardy suggests using an in-line fuse, but doesn't specify where to take the power from.  You'll need to tap into a circuit that's only live when the ignition is on; if it were mine, I'd use the heater blower circuit, same as Frigiking.  Don't use the lighter fuse, as it's hot all the time.

 

Hope that helps.

 

mike