[TR] Overdrive solenoid

[terryrs at comcast.net]

Yet another Randall e-mail that I've printed out and stuck in my file of tricks.

Have installed the 5 amp American standard blow.  (Now there's a phrase I confess I've never used before!)

Thank you Randall.

Terry

> > What did I do wrong? My guess is this thing was drawing the 
> > 15 amps all the time, instead of the brief moment to actuate. 
> 
> There are several things that can happen. One of the most commonly 
> overlooked is the "drop" when the solenoid is de-activated. It only has a 
> limited range, and if the plunger drops too far, the solenoid won't pick it 
> back up again. As you know, there is a contact in the top of the solenoid 
> that opens when the plunger reaches the upper end of it's travel, and 
> reduces the current from 15-20 amps down to 1 amp. 
> Some solenoid mounts have an adjustment for 'drop' (which may be missing or 
> misadjusted). Others had only a rubber stop, which may have fallen out or 
> distorted until it lets the solenoid drop too far. If you have the latter 
> type, I suggest you modify it to be adjustable. 
> 
> Another possibility (since the TR lacks a cover over the lever arm) is that 
> grit or a small rock got into the solenoid and blocked the plunger from 
> opening the pull-in contacts. 
> 
> Or, your solenoid may have simply been defective. There's a little plastic 
> button that pushes against the contacts, and it seems that some of them are 
> made of thermoplastic that gets soft and distorts when it gets hot. Or 
> maybe they just aren't hard enough to withstand the repeated pounding from 
> the plunger, I don't know. But I've taken one out of a burned solenoid that 
> was simply too short to open the contacts. 
> 
> My suggestion is to add a fuse to the OD solenoid circuit, sized so that it 
> will blow if the cutout contacts don't open quickly. That won't fix the 
> problem obviously, but at least it will only cost you a 50 cent fuse instead 
> of a $150 solenoid to learn you have a problem. I used a MDL 8 fuse (which 
> is an 8 amp slow-blow), just because I had a case of them on hand; but I 
> believe even a 5 amp (American) standard blow would work. I also added a 
> diode across the relay contacts, which seems to make them last longer. 
> 
> Randall