520 ignition switch

[Woodsie 51]

New Member. Resurrecting a 1991'ish 520. 20 HP Onan. Wiring has been butchered. Just fixed the valve seats, now got it running with battery wire, hot coil wire, start wire to solenoid. when i turn to starter run position, i lose power to + side of coil. Apparently another disgusting safety feature. Any thoughts on how to allevuiate this other than older model switch, or separate toggle on power to coil??.

Any response appreciated.

[TT-(Moderator) 1,156]

:WRS:

I can't see it from here but is the ignition power wire connected to the accessory ("A") or rectifier ("R") terminal instead of the ignition ("I") terminal?

Maybe it's not even the correct switch. :confusion-shrug:

[Woodsie 51]

nope i have the right terminals. have a wiring diagram. the switch was in it. talked to original owner. same switch it came with.

[Save Old Iron 1,568]

Sounds like the wiring could be bungled up forcing the ignition switch to be powered off the "A" terminal. When the ignition switch is rotated from the RUN position to the START position, the power is removed from the "A" terminal. The "I" terminal should remain hot in both RUN and START switch positions.

Trace back the wiring from the ignition coil(+) terminal thru the 9 pin connector. It SHOULD NOT end up on the "A" circuit. That would be one explanation for the loss of coil power in the START position.

Another explanation would be a defective ignition switch loosing internal contact between the "B" and the "I" terminal when the ignition switch is in the START position.

Either way .... a multimeter check to test continuity of the wiring / ignition switch will tell the story.

[Woodsie 51]

I have a 5 lug plus ground switch. Wiring diag. also shows 5 lug. 12 o'clock "start", 3 o'clock "ignition", 5 o'clock "acc",

7 o'clock "not used", 9 o'clock "battery". i have eliminated total wiring harness. ign. to coil. start to solenoid. battery to battery.

maybe a bad switch acc and ign both cut out with key turn to start position on the bench with continuity meter from battery lug to ign. lug.

old switch i have here is 6 lug does not cut off ign. power in key start position. Thanks for help. i will have rectifier charging system questions later, i have a 3 post

rectifier. again i have eliminated all other wires going to that "engine connector" block. we're goin back to basics here. somebody redid / raped this wiring.

[Save Old Iron 1,568]

the incorrect switch has "G" and "M" terminals -

the correct style switch for coil based ignition systems will have terminals labeled "A", "B", "I", "R" and "S".

[Woodsie 51]

well my 500 series user manual from the original owner shows A, B, I, R, and S, with an additional ground lug.

5posts +grnd. It matches the actual switch. i am gonna put my old switch on and wire it accordingly. considering it a bad switch. thanks for your help.

[Save Old Iron 1,568]

good, apparently we have the right switch. the demystification guide does not show a ground but no matter.

next step is to connect an ohmmeter across the I and B terminal

turn the switch to the START position. you should see continuity from I to B

[Woodsie 51]

nope thats the problem.....turn to start, lose I to B continuity. wiring in my other switch. thanks again.