My SHURflo model 4008-101-A65 on demand water pump had been acting up. On my many trips to the bathroom in the middle of the night (old man bladder), I can hear the pump pulse intermittently after I return to bed since the pump is directly below me. This can go on for some time with just a single pulse now and then. I assumed it had a small leak somewhere and would cause the pressure to keep dropping but could never find one.
Well, the pump finally quit pumping (naturally right in the middle of a nightly visit to the pot). No more pump operation. Groan.
I decided to troubleshoot the pump. I ohmed out the control switch and indeed it was wide open. I believe this switch is somewhat underrated for the constant pulsing action that these pumps sometimes do when turned on to a low flow. After I removed the switch and exercised it a bit, I was able to measure resistive contacts which may have been causing my intermittent pulse.
The repair consisted of removing the switch block (3 screws) and popping the assembly open. I used a box cutter to pop it open. Very easy! Popped out the old switch and popped in the new one. A true no brainer.
You can order a complete switch housing assembly for twice the price but it is not needed as replacing the micro switch is a breeze.
Found a link to a repair YouTube (below) which worked great for me. For only $10 I got 2 new switches from Amazon, threw in one and kept the other. Easy peasy.
Here is a link to a YouTube repair video.
Linear Mode
