Here's what I found out.
My pump:
MODEL* 4008-101-A65* * s/n 289729* * 12 VDC* *3 GPM* 7.5 amps* *Manuf date: /31/2018shut off pressure* *55 PSI
The bypass / check valve is easily accessible from the front so I'll just replace it, $13.00.
Here's some text from the operating manual:
OPERATION This pump is designed for intermittent duty only. The pump operates normally up to about 40-psi, where a spring-loaded by-pass valve opens, allowing flowback from the output side to the input side, providing smooth, steady flow with virtually no cycling, all the way down to a trickle. As a faucet is opened backup, the pressure will drop, the by-pass will close and full flow is again obtained. This allows good flow, even with today’s restrictive showers and pullout sprayer faucets. Performance will vary, of course, depending on the voltage to the pump; lower voltage = lower flow, higher voltage = higher flow. Remember your electrical safety: It is always best to shut power to the pump
ABOUT THE BY-PASS
NOTE: By-pass adjustment should only
be performed by a professional technician with proper gauges and equipment.**The by-pass is a spring loaded diaphragm that opens up allowing water*from the discharge side back to the inlet*side. The by-pass is set to begin opening*at about 40 psi and creating full by-pass*at about 62 psi (lower pressure pumps*will vary depending on the by-pass and*pressure shut-off settings). The pressure switch on the pump is set to shut
off at 55 psi. If the switch or by-pass*are adjusted too much, the by-pass and*switch shut-off can overlap and THE PUMP WILL NOT SHUT OFF.*
here's the manual
https://www.pentair.com/content/dam/...v/911-1008.pdf
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Dustin and Doris
2018 Crossroads, Sunset Trail 33CK,
38', 7600 lbs empty, 8300 lbs loaded.
2016 Tundra: 5.7L with towing package with added "Roadmaster Active Suspension"