B275 problem with switch to alternator

Mon Sep 07, 2009 10:50 pm

a friend asked me for an alternator bracket for his B275 as he knew i had changed over my gas B414 over the winter. The blocks are the same on both tractors, even though the 275 is diesel, so the alternator mounts were thought to be the same. almost true, but thats another story.

switching from pos to neg ground should not be a problem with lights, glow plugs, or the starter or selenoid, or so i thought.

the starter uses a dyer(sp?) drive to manually engage the flywheel and connect a momentary switch that controls a selenoid to provide power to the starter(Lucas). a better system than a Bendix drive as it does not eat flywheel teeth. when switched to neg ground, the starter remained engaged in the flywheel after starting, causing the selenoid to smoke from the 100 percent duty cycle. replacing the old selenoid resulted in the same issue. switching back to pos gnd after alternator disconnect cured the starter engagement issue.

it doesnt make sense to me that the mechanical drive mechanism would remain engaged simply by swapping the polarity of the battery. any ideas?

Re: B275 problem with switch to alternator

Tue Sep 08, 2009 6:06 pm

artc wrote:Switching back to pos gnd after alternator disconnect cured the starter engagement issue. Any ideas?
Guessing. Electric system back feeding the solenoid. Or the solenoid's internal wiring is holding the contact closed - once energized.

Go to your autoparts store and ask to look at their "Engine Management, Illustrated Parts Guide". Then go to the solenoid schematics. There are at least 9 different internal wiring schematics for solenoids presented.

Back feeding is easy enough to check. Start engine and manually disconnect the small solenoid feed wire. Then with the engine running, ignition switch in the on position (not start position) check for voltage at the small solenoid feed wire terminal. Same check with engine not running.

Edits: Check the solenoid - some have two small terminals. One for energizing the solenoid and one for the ignition during engine start up.

A fairly common problem (mistake) when wiring in the alternator is location of the wire energizing the alternator. If this wire is installed incorrectly you can not turn a gasoline fueled engine off with the ignition key/switch. My thought is that some how you have the wire energizing the alternator connected to the start and/or the run position on the ignition switch.

Last area to check is the ignition switch itself. Possible faulty ignition switch.

Re: B275 problem with switch to alternator

Wed Sep 09, 2009 12:32 am

artc wrote:Switching back to pos gnd after ALTERNATOR DISCONNECT cured the starter engagement issue.

it doesnt make sense to me that the mechanical drive mechanism would remain engaged simply by swapping the polarity of the battery. any ideas?

Re: B275 problem with switch to alternator

Wed Sep 09, 2009 9:49 am

eugene, you got me to thinking. i didn't hook up the alternator - i stepped into this after my friend was having the problem. i did not perform one test that i should have - 12V neg ground setup, alt disconnected. i'll bet the starter circuit will perform normally, and the alternator was connected into the start circuit - keeping it alive after releasing the start lever.

i'll check it out.

Re: B275 problem with switch to alternator

Wed Sep 09, 2009 6:25 pm

Art:

You know me, I don't know squat about most things.. but I am pretty good at pointing. So by any chance would the B-275 Manuals be of use? I have all of the manuals that I could find on the B275 loaded on the server, got them for a friend, had to scan em, so figured.. might as well put em to use. Let me know if they are useful..... :?:

Re: B275 problem with switch to alternator

Wed Sep 09, 2009 7:34 pm

Thanks Rudi, i've got most all of the B414 manuals, so pretty close. i'll remember youve got those though. give my best to Em. hope you guys are all good
art

Re: B275 problem with switch to alternator

Wed Sep 09, 2009 8:14 pm

Art:

Will have to remember that about the B414's :D Shall do.. Em is great and so are the kids. Had a great weekend - missed you though at CubFest. Hope all is well with you too. Maybe we will see you next year at Cecil's :!: