JCB 3cx help.

[Ianrm]

Are there no numbers or identification on the switch.

Now you mention it there is a no. 30 between 2 of the large pins ( my main suspect) which I believe is high current in on a relay. None of the other numbers match anyone other relay type numbers as far as I know ( like 85,86,87) could be a coincidence, but if im taking a guess, that’s a good lead

You should be able to work it out by Checking continuity on switch

ive been checking continuity on switch assuming the pin with the thickest of the 3 thick wires ( plus 2 skinny wires) is power in. Only able to trace one small pin which goes to solenoid on 2 ignition relays. One of the other pins is only active during preheat on switch, another, on, preheat and start. Of cause I’m assuming the power in is thickest wire. Have printed out 5 more tables to check continuity between all 5 pins and all others in the three key positions. That’ll be tomorrow as I’ve had a beer or three by now. Either that or I’ll connect a wire via fuse to battery to the biggest wire and try it before my brain explodes

 

[Ianrm]

Now you mention it there is a no. 30 between 2 of the large pins ( my main suspect) which I believe is high current in on a relay. None of the other numbers match anyone other relay type numbers as far as I know ( like 85,86,87) could be a coincidence, but if im taking a guess, that’s a good lead

ive been checking continuity on switch assuming the pin with the thickest of the 3 thick wires ( plus 2 skinny wires) is power in. Only able to trace one small pin which goes to solenoid on 2 ignition relays. One of the other pins is only active during preheat on switch, another, on, preheat and start. Of cause I’m assuming the power in is thickest wire. Have printed out 5 more tables to check continuity between all 5 pins and all others in the three key positions. That’ll be tomorrow as I’ve had a beer or three by now. Either that or I’ll connect a wire via fuse to battery to the biggest wire and try it before my brain explodes

Now you mention it there is a no. 30 between 2 of the large pins ( my main suspect) which I believe is high current in on a relay. None of the other numbers match anyone other relay type numbers as far as I know ( like 85,86,87) could be a coincidence, but if im taking a guess, that’s a good lead

ive been checking continuity on switch assuming the pin with the thickest of the 3 thick wires ( plus 2 skinny wires) is power in. Only able to trace one small pin which goes to solenoid on 2 ignition relays. One of the other pins is only active during preheat on switch, another, on, preheat and start. Of cause I’m assuming the power in is thickest wire. Have printed out 5 more tables to check continuity between all 5 pins and all others in the three key positions. That’ll be tomorrow as I’ve had a beer or three by now. Either that or I’ll connect a wire via fuse to battery to the biggest wire and try it before my brain explodes

am zeroing in on the prob, have identified where all but one wire goes from switch. Should be able to apply power to there to start her up and lift bucket to find the cause of no power to switch. Thing is, one of the wires from switch go to Thermostart which seem to be a fuel Pre heater for easier starting. Resistance between that wire which comes from switch to earth is only 1.1ohms. I’m guessing that that small an ohm reading would be close enough to a short that that is what took out power to switch? Measured ohms on wire alone to before heater and is close to zero. Can someone confirm that a resistance like that is bound to blow a fuse, or is that normal resistance for a small heater? Only a skinny wire running to it.

 

[Ianrm]

am zeroing in on the prob, have identified where all but one wire goes from switch. Should be able to apply power to there to start her up and lift bucket to find the cause of no power to switch. Thing is, one of the wires from switch go to Thermostart which seem to be a fuel Pre heater for easier starting. Resistance between that wire which comes from switch to earth is only 1.1ohms. I’m guessing that that small an ohm reading would be close enough to a short that that is what took out power to switch? Measured ohms on wire alone to before heater and is close to zero. Can someone confirm that a resistance like that is bound to blow a fuse, or is that normal resistance for a small heater? Only a skinny wire running to it.

Just thinking I should disconnect wire to heater and add power to it via a fuse, start low and see what it takes to blow fuse?

 

[Ianrm]

Just thinking I should disconnect wire to heater and add power to it via a fuse, start low and see what it takes to blow fuse?

Seeing as I don’t know the value of the current draw on heater

 

[Ianrm]

Just thinking I should disconnect wire to heater and add power to it via a fuse, start low and see what it takes to blow fuse?

Seeing as I don’t know the value of the current draw on heater. Could prob leave it disconnected, prob overkill for where I live in NSW Australia. Would like to know the cause tho

 

[Netherfield]

Certainly you can disconnect the thermostart if you don't need it. Only things you do need is to open the fuel solenoid and get power to the starter solenoid.

 

[Highland Mule]

Resistance between that wire which comes from switch to earth is only 1.1ohms. I’m guessing that that small an ohm reading would be close enough to a short that that is what took out power to switch?

1.1 ohms at 12V is about 11Ampere and 130Watts, which might be about right for a pre-heater.

 

[Ianrm]

Fired the old girl up today. Ran a wire from battery to power-in on switch. Still at least one prob, tachometer not working and buzzer still sounding at about 25% normal volume. Didn’t try the hydraulics or putting into gear as everything was pulled apart and wires everywhere, plus it was already way past beer o’clock. Making progress anyway. Thanks everyone for your help.

 

[3cpowertrain]

Morning all can anyone help me with a wiring diagram for the same spec machine, grey cab project 7 woth power shift gearbox. Got one where someone has cut the plug off of the loom side of the shuttle lever and need to put a new shuttle switch on.!!