High pressure blowing fuses

[chaz]

Markvii self serv plant. When selecting any high pressure function….glass fuse blows. Motor works fine when manually pushing contactor. We assume the transformer is ok as low pressure functions are fine. We have switched doors at bay and problem stays at original bay. We have tightened all wires. We suspect the contactor may be an issue? Too busy a day to switch other stuff till late tonight. Any other things to check. We did swap out Phoenix relays

 

[Fatboy769]

I would unhook the motor starter wire at the starter, turn on a high pressure function and see if fuse blows. If it does, you got a short in the motor starter wire, if not, probably a shorted coil on the starter. Should be able to unhook wire from A1 and A2 on the starter and see if you get continuity between them.

 

[chaz]

Thanks …. Issue was the diode (bridge) . upon closer examination this proprietary markvii part had swollen a bit, it’s basically diode with leads sealed in plastic. Now just to figure out if it just aged out or if there’s a root cause.