What does the OPC protect?

[srs]

The 5 amp fuse on my cabbed B3030 tractor blew while my wife was cutting the grass. She did not have the a/c on or the radio. The tractor is a 2008 model and I never had this issue before. She motioned to me that the tractor just died and when I went to start the tractor nothing happened as I turned the key, no clicking sound-nothing. I originally thought it was the safety switches but checked the fuse box and noticed the OPC fuse (5 amp) had blown. Any suggestions why this would have occurred? I had to tow the tractor up to the house, replaced the fuse and so far so good. Would hate to have this happen again in the middle of a blizzard. Thoughts anyone? Sorry if the pictures might be sideways. Thanks, Stanley

 

[ozzie tractor]

operator presence system (dunno what the c stands for) so its all the safety switches etc. check the wires behind the seat havent been damaged by stuff being plonked there. but occassionally a fuse will just die due to age and vibration.

 

[LD1]

Any suggestions why this would have occurred?

I have people as me all the time at work why a fuse blew or a breaker tripped.

My standard response.....it got too many passing through it.

Having a meter with a DC amp clamp is a nice thing. Any time I blow a fuse, I treat it as a fluke (unless something obvious). If second fuse blows....got issues and start tracing the circuit. But more times than not, the second fuse wont blow, at least not right away. Which gives ample time to have an amp clamp on the circuit and see what its pulling.

So in your case, if you are pulling 4-4.5a through that 5a fuse.....I think that you are on borrowed time and something is pulling more than it should. If its pulling less, then it would seem that you lost the first fuse just due to age/vibration as mentioned. But I would do the wiggle test. Wiggle all wiring associated with that OPC circuit, at all the switches and connectors. Then I would use all them as well. Sit on the seat, push clutch, etc. All while watching the meter. If it never waivers...all good. But its possible you got a bare section of wire (mice), that as driving the tractor, may have bounced into contact with the frame or something.

 

[von-mil]

My B3030 wiring diagram shows 5 safety switches controlled by this fuse.

PTO On/Off
PTO Rear/Mid/Both
HST Pedal Neutral/Non-neutral
Seat Tilted
Seat Occupied

These switches provide input to the controller - a small box found behind the lower dash panel (knee-height). The controller triggers the engine-stop relay and solenoid and also prevents the engine from being restarted depending on the state of the safety switches.

As LD1 suggested, try locating and inspecting the associated wiring and look for a possible short. Hopefully it was just a one-time blow and the new fuse is all you will need.

 

[srs]

Thanks guys. I'm hoping it's a one time thing. I'm approaching 500 hours so who knows. I'll try to see if there is a bare wire somewhere which will be a nightmare to find. The 5 amp fuse contains a very thin wire but looking at it under a magnifying glass it looks like it "blew" and not broke as there is a tiny burn mark inside the fuse indicating it may have shorted out. I HATE these electrical gremlins! I replaced the two safety switches (PTO on/off-PTO Rear/Mid/Both) when this fuse blew and noticed the safety switches were kinda wobbly for lack of better terms where they plugged into the wiring. The new switches were much tighter. I really appreciate everyone's advice. Thank you, Stanley

 

[Fallon]

I have people as me all the time at work why a fuse blew or a breaker tripped.

My standard response.....it got too many passing through it.

Having a meter with a DC amp clamp is a nice thing. Any time I blow a fuse, I treat it as a fluke (unless something obvious). If second fuse blows....got issues and start tracing the circuit. But more times than not, the second fuse wont blow, at least not right away. Which gives ample time to have an amp clamp on the circuit and see what its pulling.

So in your case, if you are pulling 4-4.5a through that 5a fuse.....I think that you are on borrowed time and something is pulling more than it should. If its pulling less, then it would seem that you lost the first fuse just due to age/vibration as mentioned. But I would do the wiggle test. Wiggle all wiring associated with that OPC circuit, at all the switches and connectors. Then I would use all them as well. Sit on the seat, push clutch, etc. All while watching the meter. If it never waivers...all good. But its possible you got a bare section of wire (mice), that as driving the tractor, may have bounced into contact with the frame or something.

Same... replace the fuse & carry on. If it blows again, there is something to debug.

NEVER REPLACE A FUSE WITH A HIGHER RATED ONE. It's working as designed & you want the fuse melting rather than the wiring harness (usually followed by the whole tractor).

 

[srs]

Fallon, thanks I appreciate the advice. Just weird that a tiny 5 amp fuse can disable the tractor like that. Summer time no big deal but like I previously said would hate to have that happen in the middle of a blizzard. Hopefully it was a one time thing. I can't really complain since this is an 8 year tractor and this is the only time this happened. I did buy extra 5 amp fuses which I'll keep in the tractor should this occur again. Of course I'll be searching for a bad wire at that point. Again thank you and to others for your valued opinion. Stanley

 

[Fallon]

Always a good idea to keep a box of assorted fuses around. They do just die from time to time. 40% of the time I'm replacing a fuse it just died. 50% of the time I'm working on something & do something dumb or make a design mistake resulting in the fuse doing its job. Only 10% of the time is there a problem that developed on its own repeatedly killing fuses.