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One of my cottage neighbours has a Goehner’s 12VDC water pump. It had failed in service. These pumps are designed to be on at low pressure and shut off at a preset maximum pressure. Initial tests showed infinite resistance at the power connections to the unit. Quick removal of the cover over the pressure-limiting switch showed continuity there. The problem was deeper inside the unit.

This was a case where time was saved by not doing more than essential disassembly. Because the problem looked to be electrical, I did not disassemble the in-water side. Instead, I took off the circular back cover (two long bolts with Philips heads needed to be removed). That exposed the motor electrical components. The motor brushes were still in good shape and not especially worn, but the commutator contacts were signficantly oxidized, to the extent that the brushes were not making electrical contact.

I removed the circular assembly holding the brushes, to expose the commutator contacts. I cleaned those with fine sandpaper to clear the oxide layer from them. It’s helpful for a job like this to have a vacuum cleaner on hand, and on during the job to prevent copper and copper oxide dust from getting into the motor and motor bearings.

Re-assembly was somewhat challenging in that the brushes needed to be held apart in their holder to get them back in position around the commutator. This was accomplished by using some scrap copper wire bent to temporarily hold the brushes in place. I pulled the bent copper wire out after repositioning the cover over the armature and put the two long bolts back in to complete the repair. Tests with a 12VDC battery showed the pump to be working fine again. A relatively quick repair.

This was a relatively new pump, stamped with a 2024 manufacture date. One then should ask how it could have failed with such oxidation of the contacts in such a short period of use. I’m not sure, but possibly the pump has been running often during the time since installation, and possibly in high ambient summer temperatures for much of its usage, such that a high operating temperature was increasing the oxidation rate.