RE: [DML] Bizarre electrical problem

["IN2TIME" <Gary@xxxx>]

Please excuse me if your troubleshooting has gone beyond what I'm about
to suggest. I'm not familiar with the specific circuit, and I haven't
followed all of the previous discussions, but I've done a lot of
troubleshooting on problems similar to this one.

You may be on the right track looking for a "sneak circuit" that's
keeping a voltage differential across the relay coil. Self-latching
relay circuits are designed to do what your relay is doing
inadvertently. You push a momentary-contact Start button, and the item
keeps running until you push the Stop button and break the coil circuit.

I think you've already determined this, but make sure you know if the
coil is normally grounded on one side and voltage is applied to actuate
it, or normally powered on one side and the other side is grounded to
actuate it. You have to know whether you're looking for power where it
shouldn't be or a ground where it shouldn't be. 

Read the voltage across the coil, and from each side of the coil to a
good ground:
- Before the relay is latched.
- While the relay is supposed to be latched.
- When the relay should be unlatching.

You may find that the voltage differential necessary to keep the relay
latched is always present, but that it is not high enough to actually
pull the relay in to the latched position. It doesn't take much to hold
it in the latched position once it gets there. 

At least you will have an indication of whether you have a full/partial
ground, minor leakage through a bad diode, partial voltage because the
sneak-circuit goes through another component, full voltage through a
shorted circuit, etc. 

Feel free to email me privately.

Gary
www.IN2TIME.com