# Reversing a 12 volt starter motor



## jehan12413 (Feb 4, 2010)

I have several old 12v starter motors which I am trying to reverse for a project and have been running into some problems. I am hoping that I am just overlooking something simple and that someone will point it out to me.
First of all unlike the large motors which we are used to working with these motors do not have seperate external terminals for the field and armature and the ground is through the case. Internally they have two field windings and four brushes. Two of the brushes provide the series connection to the field and the other two are connected to the case(ground). First of all I rewired the two gnd brushes to the field and the two field ones to gnd. This did reverse the direction but caused an extremely high current draw and a low rpm with virtually no torque. Could it be a brush timing issue? I assumed that due to the low voltage and RPM that they would be neutrally timed. Any help with this issue would be greatly appreciated.


----------



## hmincr (Jan 20, 2012)

On a much smaller scale than you are probably wanting, I took a 6 cylinder Johnson Outboard motor starter and did a slight rebuild to use as a winch motor for our homebuilt sawmill. 

The winch was a worm gear style.
I had an outboard motor mechanic friend that sold me a used starter and a case for cheap. I also bought 2 sets of brushes. 

Let me be perfectly clear. I know NOTHING about electronics, so, I po'boyed this setup.

Take the end cap off the starters. You need to find a space to drill out the best end cap, and install the bakelite? insulator and stud for the second set of INSULATED brushes. Use the insulated new brush set in place of the uninsulated ground brush set. Now, you have an ungrounded starter. You may need to bolt together the new insulated brushes with a lead wire to the stud. Depends on what starter you have. If brush advance is normal setting, you may also be able to widen the notch for the brush holders and rotate it slightly to change timing. 

Our winch raised and lowered the entire band saw head, so, there was about 350 pounds of weight being raised. We wore out 2 sets of gears in that winch in the 5 years we used the mill. I bought 2 ford starter solenoids for around $7.00 each. Something else would probably work, but, I was familiar with the Ford style, from the late 70's. Auto Zone had them.

You need to cross wire the switch and I used a 40A DPDT momentary toggle switch to switch the up-down action. I used 10 gauge stranded direct burial romex house wire from the solenoids to the starter. That was donated by the local electrician. That system saw probably 300-500 switching times per day, or more, on occasion. 

Hope this is similar to what you are after. I have no idea which direction was originally used as a starter speed, and, the down part of the saw head action was actually used as a fast lowering, so, it's possible I got the correct speed for the up cycle. The starter would get warm if we did a lot of sawing bigger logs. 

Changed the brushes 1 time after about 3 years of sawing.


----------



## jehan12413 (Feb 4, 2010)

Something in your post caught my eye so I double checked the brushes and sure enough they were grounding through the brush holders. When I swapped the brushes I didn't realize the rivets which hold the the two gnd brushes are not insulated from the case. Should be an easy fix now.


----------



## hmincr (Jan 20, 2012)

Hope my info helps you. The chore of insulating the leads is not near as difficult as typing all the words to explain how to do it.


----------

