NH TC40A Starting problem

[Bencaruthers]

My TC40A will crank but wont start. Need some help troubleshooting. This is how far I’ve got:

Checked the fuel lines, changed the fuel filter, manually bled the the system at the injector pump bleed valve. Did not fix the prob.

Unplugged connector at Fuel Shutoff Solenoid, jumped from battery direct to solenoid, cranked right up. Checked volts to the light blue line going to the solenoid, no volts. So narrowing it down at this point.

Traced connecting line back to the #4 relay, checked for continuity with ohmmeter, good there ( surprising since mice had made a nice home in there).

Thought maybe a bad relay, so switched #4 relay with #1 relay, but no change.

Got on here, read a ton of good info. Saw where it could be the seat switch or bypass wiring.

Unplugged the seat switch and tried jumping connection with a piece of copper wire. No change, and still no power to connector at solenoid.

Heading back to the farm today to continue working on it. Any help would be greatly appreciated!

Could it be the 8amp circuit breaker on the buss bar? Possibly a problem with the ignition sending power?

Thanks in advance.
Ben

 

[dlctcg]

So, the seat switch and the parking brake switch are the ones that control the fuel solenoid to shut off. Being you already jumpered seat switch for testing... did you make sure the parking brake was set & the Dash Light was on? The lever needs to be pulled up to engage the switch...

These two switches will not stop the engine from turning over which the tractor seems to be doing...

The #4 Relay is a latching relay & sounds like to tested & even swapped it with a known good one... not sure your model is the same config as ours but check for the Neutral Start Relay & make sure its good & wires are not chewed... Relay #9 in this PDF... but this is for a TC40D so just confirm for your tractor...





If the any of the follow 3 were the issue, 8amp breaker, the neutral safety or PTO safety switch the tractor will not turn over / crank. So I think the breaker is good...

Definitely double check the wiring for chewed wires... mice are known for building nests there & messing things up... so look really good...

 

[Bencaruthers]

Thanks for the quick reply! Good info! Yes, that’s the same diagram in my owners manual.
Yes i switched the relay with one that I confirmed good.

Haven’t checked the #9 neutral start relay yet. Does that send a signal directly to the solenoid, or to the #4relay which in turns send signal to solenoid?

Ill check the #9 relay, the parking break switch, and look for chewed wires again and let you know.

thanks again!

 

[Bencaruthers]

Ok, so parking brake set and dash light is on. Assuming that means the safety switch is ok. Seat switch still jumped, and still no power to solenoid. Checked and cleaned #9 relay and wires. All looked ok. Swapped #8 and #9 relays as a check, still no power to solenoid.

Could it be the Operator Safety Module? I traced the light blue line to the #4relay with ohmmeter, looked fine. Traced the white wire to the seat switch, looked fine. Could it be a bad circuit board in that module(assuming that’s a circuit board in there)?

 

[Bencaruthers]

Alright, figured out the problem!! It is in fact the Operator Safety Module. Either the connectors, or the actual board inside. Jumped across the safety’s from the blue wire connection(to solenoid) directly to black wire connection(ground) in the module itself....turned the key and and got power to solenoid!!
Feels good to get that fixed! Thanks for the helpful tips dlctcg! That definitely helped with figuring it out.

 

[dlctcg]

Glad you could trace it down...

 

[thclimer]

And thanks for letting us know what you found so that others in the future can possibly benefit.

 

[Bencaruthers]

No problem. This forum is a great source of info!
I don’t really want to leave the Operator Safety Module jumped since it bypasses the seat safety and the parking break safety features full time(wouldn’t recommend jumping safety’s). So my only other question now is, do I buy a new OEM Operator Safety Module for $65 plus shipping....., or is there a reason I couldn’t just use a cheap Bosch relay that could basically perform the same function?

 

[DieselMonk]

There is another safety switch at the PTO lever. That’s what my old TC55DA’s problem was.

 

[greg0145]

I'm going to tag on to this thread...
My TC40D starter does not engage. When I turn the key to the start position the PTO On indicator is also illuminated. I've only had the tractor for 15 or 20 years so I don't recall if that light is supposed to be on at any time other than when the PTO is engaged. I jiggled the PTO handle and checked the parking brake and the range selector. Has anyone had a problem with the PTO switch and how do I find it? Or is there a bundle of wires under the instrument panel or behind cowling below the steering wheel that I should be checking first?