[TR] Overdrive Solenoids aftermarket

[TERRY SMITH]

Yep.  Bought an aftermarket solenoid and pulled the tranny tunnel.  Inspection of the old solenoid found the switch actuated by the plunger wasn't operational.  New solenoid has relieved all problems.


Thank you again.  It's soooooo nice flipping the OD switch and having something happen other than a popped fuse!


Terry

> On March 10, 2017 at 5:48 PM Randall <TR3driver at ca.rr.com> wrote:
> 
> 
>     > Thank you, Randall.  Maybe that's the problem.  I had added a modern two
> 
>     > prong mini 10 amp fuse.  Don't remember why, but I thought the amp was in
> 
>     > the 3 to 5 range, but that must not be for pull in.  I'll try switching to
> 
>     > a slo-blo fuse at 8 amp too and see what happens.
> 
>      
> 
>     No point, IMO.  From your description, I do think you have a problem.  Might be an internal short in the "holding" coil (which should draw only about 1 amp), but my guess is that the pull-in contacts are not opening for some reason, or are closing back up again when things get hot.
> 
>      
> 
>     Just so we're on the same page, the A-type solenoid has two windings internally.  When the relay first closes, current passes through both windings, producing a big strong jolt of magnetism to move the solenoid plunger.  Once the plunger has reached the end of it's travel (against the inside of the housing), it is supposed to press on a small button that pushes open the contacts under the housing outside, and cuts the current through the high current "pull-in" coil.  This should happen very quickly, normally too fast to blow a 10 amp fuse.  The pull-in coil draws somewhere around 15-20 amps, while the holding coil is only about 1 amp.
> 
>      
> 
>     Here's a photo where you can kind of see the black button under the contact lever.  https://goo.gl/W5Q23V
> 
>     (Ignore the diode, it was a mistake.)
> 
>      
> 
>     I only used the MDL-8 fuse because I had a box of them on hand (scrounged from the trash when a previous employer shut down a production line).  Your 10 amp mini fuse should work just fine.
> 
>      
> 
>     Anything that blocks the solenoid plunger from rising all the way can cause the fuse to blow.  In my case, it appeared to be a bit of gravel that found its way inside and jammed the plunger.  But misadjustment of the linkage can do it too, or even losing the stop that controls how far the plunger can drop out of the solenoid.  (On some A-types, there is supposed to be a little rubber bumper mounted on the stop arm.  Mine was missing, so I replaced it with a bolt.
> 
>     http://s258.photobucket.com/user/TR3driver/media/A-type%20OD/DSCF0055.jpg.html
> 
>      
> 
>     Randall
> 


 

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