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Customer complained no crank, no start. I charged battery and it started and ran fine but the battery was not charging. I found the stator was outputting the 28 volts AC and I had BV between the tractor side B+ lead at the regulator and ground. I had proven good power and ground to regulator and a good circuit from the regulator to the battery, so I diagnosed a bad regulator and replaced it. It was not the problem, the battery was still not charging. 4 hours of troubleshooting later, I noticed each of the AC wires in the regulator plug had one extra wire along side it, which I have not noticed on other equipment. I followed these wires to one of three ice cube relays under the gas tank and read on the relay that the stator is shorted to itself when the key is off, but the relay creates an open between the two AC leads when in the run or start position. This relay was not opening and appeared to cause my problem. I switched around the relays as they are all the same, and the problem persisted. I checked control power on the relay, it had BV with the key on. I knew this because it clicked, but I wanted to be thorough. What I have is a relay with no function on this tractor other than to short the stator leads to each other when the machine is turned off and open them when it is on or starting. The relay is receiving good consistent power but not opening the circuit no matter which of the relays I swap in its place, yet those relays work when placed in other circuits. What I've done is cut one of the AC lines to this relay so they are never shorted to each other, and now the battery is charging 14V. The tractor starts and runs fine, and appears to have no issues, so my question; Why does that relay exist, is there any reason the two AC leads from the stator need to be shorted to each other when the tractor is turned off or am I missing something here? I have included the wiring diagram for your reference.
 

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A few thoughts... I would check that the ignition switch operates as the connection table on the schematic shows.
When the key is ON, and you occupy the drivers seat, all relays should operate. You should hear them click, or feel them when either the switch is move to ON or OFF, or the seat switch opens/closes.
If you check the switch table, the charging output is routed through the ignition switch. If the switch is worn out, it may not make good enough contact to pass the current needed to charge.
I think the second relay that shorts the charge output is to remove B+ from the ignition(so it won't run with the ignition OFF). It is not a standard 'magneto' where the ignition is grounded by the switch, so you have to remove battery power to disable the ignition.
I think I would use a bulb-style test light rather than a VOM when checking for continuity. You may have some worn contacts on the relays, or inside the ignition switch, that show 'good' with a VOM, but cannot pass the actual current needed.
tom
 
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