Solenoid Diode

[Threeput]

Having worked with 48v DC relays in the Telephone Industry...there was always a diode in reverse across the coil terminals...this was to discharge the collapsing field when relay was switched off so it didn't send a high voltage low current into the system...is there something in these solenoids that discharges this collapsing field?

[scottyb]

With electronic speed controllers there should be an external diode 1a 1000v on all 36v carts and 3a 1000v on all 48v carts. some solenoids and controllers have built in diodes.

[Threeput]

OK,,,so if you are testing the continuity of a solenoid coil.. which is open for example... that has a built in diode..then polarity of the testing prods would have to match the coil polarity or you would get a reading across the diode if the testing prods were reversed,,,,name of the game I guess is "be aware"

[yurtle]

Or just remove one side.

[Threeput]

Right.. removing one side would work if you can remove it...but as Scottyb pointed out some solenoids have the diode built in...which I would think inaccessible

[radioman]

A lot of modern digital test meters will not bias a silicon diode junction in the forward direction to get a reliable indication if it is good or bad unless the diode is shorted. I use an old Simpson 260 multimeter on the RX1 scale to check diode reverse and forward functions. It takes about .7 volts to forward bias a silicon diode junction and a lot of meters don't put out that much voltage on the test probes.

[Threeput]

Good info radioman..thanks