The original overload is cutting out after running a while, and I've measured the compressor is only pulling 0.9 amps when running so I suspect it may be past it.
Ive read the specs off the compressor ( R 1/2 25 Volts 230 cycles 50 Amps 9.4). Either im misreading the corroded compressor plate, or 9.4amps is some form of starting peak.
When I did measure the starting peak, the DMM saw 4.5 amps, a quick flash to 14, then running consistently at 0.98 amps. Im not sure of the 14amp reading, as the meter is only specced to read 10, and with a 5 amp fuse on the whole appliance which has not blown to date, I cant see 14 being accurate. In addition the 5amp fuse is also protecting the arduino PSU, and I think the arduino itself with relay control and temp sensor must pull a few hundred ma.
Im looking into some combined start/overload devices like the Supco RCO 820, which will also tidy up the wiring. Their products are often ranged from say 1/12 HP to 1/6, So in terms of overload Im not 100% I'd be happy with a generic product. What I might do is also add a hall effect current sensor to the arduino and add my own overload control in the software as its fun and I like over-engineering
