Upgrading Kubota T1400 safeties

[38racing]

My neighbour gave me his T1400H. By design you can't get off seat with blades PTO engaged (lever). You can get off if pto is off. Maybe it is because of older safety features or because the hydro drive by pedal should seek neutral if no operator. I want it so you can only leave seat if pto is off and brake is on. It's being a bit of a challenge. The safety switches all pass 12v to a relay pack (relays not accessible) rather than grounding the kill circuit directly. The seat switch is single pole and no easy way to replace with double pole or add additional switch. Brake was single pole but I was able to add a second switch. The part that's complicating it is that the PTO switch circuit enters the relay pack to control 2 relays. However it exits the pack to feed the carb solenoid on the same connector that's inputting to the pack and feeding carb from the seat switch. There's an internal diode to prevent seat input affecting crank circuit. The effect is that if I try to use the seat +ve feed it's in parallel with PTO. So if PTO is off it's also like saying your are on the seat. Despite the schematic showing this I still tried first 1 relay , then 2 in the feed to the carb solenoid . I'm thinking now that if I put a diode in the right place in the feed from seat to relay pack then I can isolate the feed to my new relay from the seat and have no signal to it from the PTO, while still having the seat feed the relay pact and the carb solenoid.
I'm assuming that a diode from a briggs dual charging setup should handle this. I notice that the relay pack schematic shows diodes across the relay coil connections. How important is that to have on the relays I'm adding?

[KE4AVB]

A basic AND gate operation. Fairly straight forward wiring.

The new brake switch either needs to be a double pole or two of them that are normally open.

Once you have the correct switch(s) run 12vdc from the ignition switch run terminal (IE switched 12vdc) to the new brake switch. This so the relay will only receive power with in run and start positions. From there run a lead to the relay coil and ground the other terminal. This get the relay to operate when the clutch/brake pedal is fully depressed. Now break the lead between the relay pack and the PTO switch. Now connect this break to the relay terminal that are close when power is applied. Now with this setup both the clutch switch and PTO switch must be closed in order for power to be applied to the relay pack. This leaves the switch operational while mowing in case the operator is knocked off the seat. It also ensures that when the PTO is off (switch closed) that power is applied via the relay pack so the starter will work when the clutch pedal is fully depressed activating both circuits.

Caution don't try this with a single pole switch clutch/brake switch or the starter will operate continuously when the pedal is depressed fully. It requires either a double pole switch or two separate switches.

The diodes across are there just to prevent relay chatter as inductive kick occurs as the coil magnetic field collapses. Not totally necessary but is recommended as I have seen relays to latch up because of this. One of the diodes in the relay pack is just a steering diode to prevent the starter relay from being active when the PTO is in use.

Does this make sense?

[38racing]

Going to study what you propose. I have 2 switches for the brake but only can have 1 for pto and and seat. Had not thought about pulling pto lead from pack and having it connected to a relay to keep the cranking circuit. Although somehow pto might still have feed the coil kill circuit relay and that's where it feeds back out.

[KE4AVB]

Maybe the following diagram will help. Sorry for the hand drawing, I haven't figured out how the scan directly into Openoffice Draw yet.

Kubota T1400 wiring mod

[38racing]

Well, before getting back here I put the diode in and everything sees to work the way I want but boy your idea is simpler. Basically it's using the 2nd brake switch to make it look like the pto is on if the brake is out. That means if you get off seat with brake out it's like getting off seat with pto on and existing safety circuit shuts it down With brake on the PTO circuit is back to normal path and needs to be off for cranking and of course brake is already on to allow cranking through the original safety switch.