The diagnosis!: 91 L2550. Starter won't engage. click/click. new Alt & Reg recently.
Pic of putting meter on RED G lug wire. and other lead on AC lug which is RUN and should be 0 ohms or short internally to pass the 12 V to keep ol' Orange running happy.
NOTE- A Day later.... New switch arrived 10am. Installed and she fired right up! ). Case closed.
Short Summary of what the write up below all means:
Basically, the TRactor was hard to start for over a month. I would turn on and off. on and off. It turns out that when you turn the key to START, it must short out 3 internal contacts to the center red 12V contact and pass the 12V to all those places. Missing even 1 contact means... no start. To test this you need a meter to test for your switch's internal shorting. You will connect to the RED wire terminal ( see pic above) and move the other lead around to the other 3 wires via the process below.
If your HEATER is bad, that switch position connects out the rear on a separate lug and a separate wire that goes over to the heater indicator. Just test on the open lug. There is no wire for the heater on that 4 wire plug.
Ok - Top Image is from the back of the manual. IT's a terminal matrix for the ignition unit. It shows the connections and what happens on each lug when you turn the key. I mean, RTMF sometimes works right. :hehe long day. I know it's blurry in the image but I can confirm I've got a bad Ignition switch. It's pulled out and I'm across the 4 contacts w/ my Meter in Ohms Mode. From the chart on the manual wiring page you can see (not in this image) which colors are used for each of the lines as (see full testing desc. below) BR BW R and RW color wires. These colors should match up w/ your harness 4 lug connector as:
BATT- Red wire and noted as G lug. (center lug folks).
G1 = solid line over to Heater indicator element. N/A for this test. uless your heater is not working.
G2 = Black White-
ST = Black Red.
AC = Red White.
Unless I'm missing something, here is the test I've done.
From the chart you can then ohm out the lines needed to short internally from BATT (G red wire lug) to the other harness lugs which travel to the places needing power.
Connect 1 meter lead to RED/BATT/G (lug in center).
To Start ohm test:
Connect other meter lead to ST/Black-Red lug. Turn Key to start. Should go to Zero ohms. Move lead from ST to G2/Black Red lug. Turn key to Start. Should go to zero ohms. Move lead to AC/Red-White lug. Turn key to start. should go to Zero ohm. These 3 zero ohm conditions are needed to start the tractor.
then back from spring loaded START to RUN...
To Run ohm test:
one lead on Red wire lug. (G) center lead. Other on AC lead (red white). should be zero ohms.
What my ignition switch does on the bench: I can get the START position to Ohm to zero on the 3 lugs but only by really twisting and pressing and playing.
- So that why it'll start when I yank and crank the key.
to Run: should be a short on BATT to AC. (red/white) wire. And no matter what in RUN selection, I cannot get it to zero out. So that's broken internally and why the tractor instantly stops when I go from START to RUN... (god Ihope)
to pull the ignition was only a few mins work. Don't hesitate if you think it's hard. It's not. Untwist the heater indicator top and press thru. There is enough slack to then pull off the cowling and disconnect the two harness connectors and your off the tractor w/ the assy. Taking the ignition switch out was just unscrewing the top cap and pushing it thought too.
So.. glad I put that on hot order overnight earlier b4 the overnight deadline.
I hope this can help someone in the future. It was no fun to get to diagnoses, but not too expensive in parts.
