Skip to main content

Reply to "overheating solenoid"

@dkdkrd posted:

Talk about commiseration!....

Some time ago I sought help (OP of thread) on renovating an old Lionel No.80 semaphore I got in a purchase of....stuff.  Needed help on it....from my wife's perseverance in online searching.

The second item...rewinding the solenoid coil...I never found an answer to... How many coils of wire should be on the solenoid?  There were 30 coils (3/8" total length on a 1" armature) and lot of witness of additional coils on the underlying tape wrap.  One posting said that these old standard gauge accessories were very over-designed, so I surmised that a full wrap of the number 28awg wire for the 1" length (approx. 80 coils) would be a good try. 

I found a local electric motor repair shop that rewinds armatures.  He gave me 50' of 28awg enameled wire, no charge!  I wound the solenoid, taped it with high-temp 3M No.27 electrical glass tape with thermsetting adhesive.  Jury-rigged a set up with the core plunger suspended above on a rubber band.  Applied 12v to the coil, and BAM!!.....worked like spring-loaded mousetrap!  Sez I, 'I'm home free!'

Assembled it into  the semaphore, wired per the Lionel instructions my wife found, applied the same 12v from the same old MRC O27 Dual powerpack (80VA) I had used for all my workbench repairs and the test of the newly wrapped coil, and....immediately got an 'overload' on the powerpack! 

Applied power to the light bulb leads......OK.

Applied power to the solenoid leads, mounted in the semaphore base,....Overload!

Both solenoid coil leads are free.  VOM confirms the coil is not shorted to the coil armature.

The mechanical actuation of the semaphore arm is clean, aligned, and works smoothly/freely with finger pressure.  

I do not often give up on something electro-mechanically simple like this accessory, but I'm on the brink.

Any ideas?  I'm beyond give me the 'Duh!'...if there is one.


Any wire left? Measure resistance for about 10' of it.

Esitimate length on the coil.

Now measure the coil añd compare actual Ohm value to the test length measurement.

You might be able to find a large enough difference to detect a short in the coil as ohms will be too low if it is shorted. 

OGR Publishing, Inc., 1310 Eastside Centre Ct, Suite 6, Mountain Home, AR 72653