Makita MAC700/Sunny pressure switch won't turn on
by Jay Levitt
Makita MAC700/Sunny pressure switch
Short version: The black reset/test button inside the pressure switch stays in the "off" position.
Long version: The compressor won't turn on; circuit breaker is fine, verified no power to the motor with a multimeter. The pressure switch is a Sunny SP-204/E211960/EE252248, which looks suspiciously like a Leeho LF10-4H. The "motor" terminals are not connecting to the "line" terminals; they stay open. This seems to be a purely mechanical problem in the pressure switch; it happens with no air in the tank or lines, and no power.
When I remove the cover of the pressure switch, there's a black plastic button between the motor terminals - the Leeho manual says it's a test button. When I turn the main power switch to "on", and press the black button, it pushes the switch contacts down to make contact. But when I turn the power switch "off", the black button pops back up, and the contacts spring open again and stay there.
I know pressure switches fail eventually, and the unit's 7 years old, but this is a little baffling - the only time I've touched the compressor was to borrow the air-side regulator adapter nipple (and replace it, of course). I can't imagine how that'd cause the pressure switch to start mechanically failing, and before I replace the switch, I'm wondering if there's something obvious I'm missing. I've played with the cut-in/out and the cut-out screws, I've removed and reattached the unload cable, I've tried wiggling various parts of the contact springs... any ideas?
If there is no pressure in the tank, and you plug the compressor in, power should flow through the switch to the motor circuit. If that does not happen, the pressure switch is pooched.
To my knowledge there are no user serviceable parts or repairs reasonably possible for a low cost pressure switch.
It were my compressor, I'd find a pressure switch that fits the footprint, including operating the unloader, and replace the old one.