Electrical: Bench test a 6V starter

[Jeff_H]

Well, this is not a studebaker starter, but its a 6V starter non the less so probably the same enough that the topic has value here.

Can you expect to be able to spin the starter using a battery charger for power? Starter sitting on the bench, armature will turn by hand. Starters being series field I know they take a pretty huge current at low speed. But, w/o any load should it at least turn some?

I've never tried to bench test a starter before so not sure how much no-load current is needed. My attempt just pegged the ammeter on the charger and the shaft didn't so much as twitch. If I had some jumper cables on hand I would have used a half dead 12v battery instead.

The reason for looking at this was I pulled this out of a tractor that would turn over SO SLOOOOOOOW that I found hand cranking it to be faster. Really. Often the bendix wouldnt even spin out on the nose it was so slow. Wiring on the tractor is poor and the starter switch (direct acting, no solenoid) could be shot but since I don't think the starter has been checked out for at least 40yrs (more like 50+) it was worth looking at it. I got it apart and the brushes seemed OK for wear, bushings OK (not egged out), and armature not dragging on the fields. Unless there is a bad winding, Its probably fine. I cleaned up the commutator with some fine sandpaper, scraped out the carbon buildup out between the segments and put some fresh grease on the bushings and put it back together. But, Id still like to verify it will spin.

[whacker]

Jumpering it with a half-dead 12V battery isn't going to prove anything. A twelve volt battery will put out 12 volts, even if it isn't very powerful. You need to jump it off the 6V battery in the tractor, if that is what you want to do. Your starting problem is most likely not in the starter, but in the electrical connections, and in the 6V battery. Most batteries are only good for 5 years at best. Cheapo 6 volt tar top batteries are only good for 3, usually. How old is that battery in the tractor? 6 volt systems are very sensitive to resistance. You need to start at the battery, cleaning every connection to shiny raw metal. Baking soda dissolved in water will clean battery corrosion. Wire brush every copper or brass connection. Put the starter back in and try it again.

[Jeff_H]

Yes, I'd agree the issues are more likely in the wiring. A no load test is not going to prove it puts out full torque either. It will show I dont have a fatal fault like a shorted winding I would hope though. Tractor had not been run in about 2 yrs and the battery is about 5-6yrs old and has been sitting in the shed for at least 2yrs I'd say. Don't have it here anyway. Tractor is 200 miles from here. When I had it running a month or so ago I didn't even bother to put the battery in and just hand cranked it. I don't know how slow it was the last time started on the current battery (my late Dad had it running in 2010 I think but not sure) but a few years prior to that when either that or a prior battery was there when I personally last started the tractor it was nearly impossible to start. Half the time the bendix wouldnt spin out and engage the ring gear it was so slow. I figured it wasn't a bad idea to at least check over the starter even though the real problems are more likely poor wiring. All the wiring on this tractor is original and over 60 years old. From what I am reading, this isnt going to work unless I have a battery since the inrush current is too high for any charger or booster to work as even a bench test. I just want to make sure the thing at least will spin after having it apart before putting it back in. There isnt much to the starter circuit fortunately. I ground cable, I short cable to the direct acting push switch, and a longer one from there to the starter. My bet is most of the problem is that switch. I even found a new switch in the shed that looks like its been there for 30yrs! Dunno why it was never installed.

[njonkman]

Well I have been rebuilding starter for over 50 years. I start my 6 volt tractor with a 12 volt battery all the time. I also do the spin test on the bench with the same battery. It only needs a second to see that it spins. As to the bendix not coming out is sometimes caused by the lubricant on the shaft getting too old and sticky. Make sure you put some light lubricant on there when reassembling it.
You really need to do some continuity tests and should have growler test while apart but if it will spin with a touch of 12 volt on the terminal than it likely will do the job for you.
Nick