Nobody seems to have solved your 'latch on' conundrum.
You didn't provide quite enough information for us to be sure what you 
are doing.

Can you provide a full circuit of the relevant portion OR describe it 
fully.

How big is the base drive resistor? [[reads more ]] - OK, 1 k

When you turn it off, how do you do it - do you ground the resistor 
input via  PIC pin or  float the driving pin.

It sounds as though you may have base leakage problems BUT the 1 k 
drive should be amply low enough if you are grounding the input.

If you ground the input to the 1K resistor when the large solenoid is 
on, does it till stay on?


        Russell McMahon 

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