Mechanical Relay Board for VacuMaid / AstroVac P125, SR42 & MK-X Central Vacuums

Central vacuum power units built by VacuMaid and sold under the AstroVac name switch their high-voltage motor circuit through a mechanical relay rather than a solid-state board, and this is the replacement relay for that circuit. It reads the low-voltage start signal coming from a wall inlet or the hose handle and closes the relay contacts to run the motor.

This relay board fits the P125 power unit, the MK-X series, and the SR42, and parts listings match it across the wider SR family as well: SR-40, SR-41, SR-43, SR-82, and SR-88. VacuMaid sells it as its 120V transformer and relay assembly, so the transformer that steps household current down to the control side rides on the same board. Dual-motor units in this family need one board per motor, so check the wiring inside your canister, or count the boards already installed, before deciding how many to order. Mechanical relays wear differently than solid-state switching components; their contacts arc slightly with every cycle, and over thousands of on/off cycles that arcing pits the contact surface until it either fails to close reliably or welds itself shut under load.

A power unit that will not start, one that runs continuously once plugged in, or one that has stopped responding to the wall switches often points to a relay that has worn out or welded its contacts shut. Replacing the relay board is a straightforward fix that avoids swapping the entire power unit, and it is usually the first thing worth checking on an older unit before assuming the motor itself has failed.

Disconnect the power unit before opening the canister, and inspect the relay contacts for pitting or discoloration as a visual confirmation of the failure before installing the replacement.

• Part: P12595A
• Power units: VacuMaid and AstroVac P125, MK-X, and the SR family: SR-40, SR-41, SR-42, SR-43, SR-82, SR-88
• Type: mechanical relay board
• Function: low-voltage signal switches the high-voltage motor circuit