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Per at Soggers has recently had an enquiry about converting from a dynamo to an alternator on a FE35.  If you haven’t allready had a look at Per’s website then Vintage Tractor Engineer would recommend it as an interesting read about his FE35 tractor.

Per Said:-

I’ve had an inquiry about converting from a Lucas dynamo to a Delco 10-SI alternator. This fellow has an FE35 which is earlier than 1959, and it presently uses positive ground. I believe older models came with positive ground whereas my own ’59 has negative ground. I don’t know if that is original or if it has been changed later.
His question is: since the new alternator needs negative ground, how do you convert the starter motor to negative ground? In order to maintain the correct direction of rotation (clockwise as seen from the transmission) do you simply reverse the plus and minus wires on the starter? I.e., do you now attach the positive battery wire to the top terminal on the solenoid and the (now negative) ground wire to the post on the end of the starter casing?
Thanks for any thoughts you or Ian may have on this.

Then before we had chance to reply, Per e-mailed us again:-

Hi Steve,

I think the problem about converting an FE35 starter motor from pos to neg ground has been solved. Here’s what an auto-electric expert wrote:
“The starter motor doesn’t care about polarity so you don’t have to change those cables. Same with switches, lights, solenoids and the like. Most ammeters will indicate backwards unless you swap the wires from one post to the other and vice versa. Swap the cables on the battery, wire the alternator like your schema shows, turn on the lights to check the ammeter shows discharge and that should be all.”

We then gave Per a few more things to consider…..

Hi Per,

It is the same starter motor on the MF135 (-ve earth) as on the MF35 (+ve earth), so I would think that it is just a case of swapping the battery leads over as you suggested.

The gentleman will need to make sure that the voltage regulator box is
disconnected and the wires made safe.

Also will need to swap the ammeter wires over.

Also consider the max output in Amps of the altenator and the corresponding size of the wire to carry this current.

Also consider the maximum capacity (Amps) of the ammeter when choosing the altenator output current.

Hope this helps.


Steve and Ian.