A few years ago I was curious about the compressor cycling characteristics of my Suburban's Sanden at road speed... how long on, how long off, w/ F&R air in operation.
I hooked-up a light to the compressor clutch circuit at the clutch control relay (firewall location) and used a length of wire to snake from there into the cab so as to position the light atop the dash.
I drove from IL to northern WI (Tomahawk) for the weekend. Engine RPM at 70MPH is around 2200. Compressor RPM thus about 4000RPM (200mm crank pulley, 112mm compressor pulley).
What I found was interesting, at least to me. The compressor would run for what seemed like a
long time... and I'm sorry I didn't measure it with a stopwatch, but I might guess 45s. And then it would shut off for a long time, roughly (
roughly) about the same length of time.
These ON / OFF times were longer than I was used to seeing, e.g., on my smallish 1995 S10 Blazer w/ R4 compressor and R134 (a vehicle I no longer own).
What did I learn? The Suburban's large amount of refrigerant, and the large volume of plumbing in the system (long tubes to the back acting as accumulators on both high and low sides), meant the compressor had long ON times to move large amounts of refrigerant from one large space into another and, accordingly, long OFF times as those large spaces equalized.
I would be interested to see
@Wildblue19's compressor's cycling behavior under conditions similar to mine or
@L31MaxExpress.
My Suburban's in storage so I can't run out and make measurements right now.