jinman
Rest in Peace
- Joined
- Feb 23, 2001
- Messages
- 20,387
- Location
- Texas - Wise County - Sunset
- Tractor
- NHTC45D, NH LB75B, Ford Jubilee
</font><font color="blue" class="small">( Are the Starter and the Glow Plugs on the same fuse in the Class III? )</font>
Chris, as in most starters, there is no protection between the battery and the solenoid. The positive lead from the battery goes directly to the solenoid and then power is distributed from that point to all other accessories through the 40 amp main fuse. When the starter solenoid closes, the starter motor's load is connected directly to the battery. Because there may be such a wide variation in current required for different starting conditions, this circuit is most often not fused (Some on TBN have even used their starters to move the tractor when the engine will not start). /forums/images/graemlins/smirk.gif If there is a direct short in the starter, a conflagration will surely follow. /forums/images/graemlins/shocked.gif
The circuit for the glow plugs is divided into power and control. The control for the glow plug relay (coil circuit) and timer is fed from the infamous 7.5 amp fuse for the safety interlock circuit. The power for the glow plugs comes directly from a branch off the 40 amp fuse through the glow plug relay contacts to the glow plugs. The glow plug timer is in the power relay coil circuit. When it times out, it removes the power from the glow plug power relay's coil and the contacts open up. Am I making sense here? /forums/images/graemlins/crazy.gif
So, the use of the starter can cause a heavy load on the battery that will make it's output voltage drop if the battery is not in peak condition. That lowering of the voltage or a low battery in general could cause the glowplugs to pull more current. Generally, heating elements use large currents initially, and as the metal heats up the resistance of the device increases and the current to sustain the heat drops. In the case of the glow plugs, my theory is that they never get to their proper heat, and thus the additional current requirement is enough to blow the 7.5 amp slo-blo fuse. I think this circuit on the NH CUTs is just right on the edge. That's why I put in a 10 amp fuse. It seems to have solved my problem. /forums/images/graemlins/grin.gif
Chris, as in most starters, there is no protection between the battery and the solenoid. The positive lead from the battery goes directly to the solenoid and then power is distributed from that point to all other accessories through the 40 amp main fuse. When the starter solenoid closes, the starter motor's load is connected directly to the battery. Because there may be such a wide variation in current required for different starting conditions, this circuit is most often not fused (Some on TBN have even used their starters to move the tractor when the engine will not start). /forums/images/graemlins/smirk.gif If there is a direct short in the starter, a conflagration will surely follow. /forums/images/graemlins/shocked.gif
The circuit for the glow plugs is divided into power and control. The control for the glow plug relay (coil circuit) and timer is fed from the infamous 7.5 amp fuse for the safety interlock circuit. The power for the glow plugs comes directly from a branch off the 40 amp fuse through the glow plug relay contacts to the glow plugs. The glow plug timer is in the power relay coil circuit. When it times out, it removes the power from the glow plug power relay's coil and the contacts open up. Am I making sense here? /forums/images/graemlins/crazy.gif
So, the use of the starter can cause a heavy load on the battery that will make it's output voltage drop if the battery is not in peak condition. That lowering of the voltage or a low battery in general could cause the glowplugs to pull more current. Generally, heating elements use large currents initially, and as the metal heats up the resistance of the device increases and the current to sustain the heat drops. In the case of the glow plugs, my theory is that they never get to their proper heat, and thus the additional current requirement is enough to blow the 7.5 amp slo-blo fuse. I think this circuit on the NH CUTs is just right on the edge. That's why I put in a 10 amp fuse. It seems to have solved my problem. /forums/images/graemlins/grin.gif