Jowett falcon battery leads positions

[MartinRaine]

Hi can anyone tell me wear the positive lead from the starter button runs to the starter mortor is it inside the car and if so the position. Also i know the earth lead from the battery runs through the bulkhead but then i do not know wear it runs and to what it should be connected to. Thanks Martin

[Forumadmin]

I do not know the Falcon; but the earth lead should be fixed close to the starter, probably under the bolt that fixes it to the engine. There should also be an earth strap from the engine to the chassis. On the positive side (if indeed you have a negative earth system) the main lead from the battery would need to go starter push and the output from the push would go to the starter. I could not find a diagram in the gallery! Alistair!

[george garside]

the 1936 7hp wiring diagram simply shows a heavy leaad going from battery to starter switch on dashboard and another from starter switch to starter motor.There is also a lead from battery terminal on starter switch to ammeter

[Alastair Gregg]

Falcon or model specific details are currently a bit sketchy. Indeed anything pre war is fairly limited, if you have anything you could contribute Gentlemen I would be very keen to make it part of the Legacy project.

[Tony Fearn]

There is also a lead from battery terminal on starter switch to ammeter

I've a feeling that this wire is about the thickness of the earth wire in those grey house wiring looms, i.e not your average wire. I don't know why, but it must be that there's a lot of current going through it.

Do we have any 'auto-electricians' able to verify this?

Tony.

[Robin Fairservice]

I am an Engineer, not an electrician, but from what I have read in the previous posts, this cable has to carry enough Amps to start the engine; hence it needs to be hefty. Nowadays there is a solenoid to connect the battery to the starter, so the wiring from the starter switch to the solenoid can be lighter.

[george garside]

the wires from the starter switch to the ammeter & from ammeter to cut out on dynamo need to be able to carry at least 10 amps (plus safety margin) as the charging rate is 7-8 amps at 30mph. probably going up to around 10 amps with; aid of wind & gradient!

the main starter leads from battery to switch & switch to starter motor have to carry the full starter load which at a guess could be around 50 amps which is why they are so thick. Most other makers either fitted the switch on the starter motror with a cable pull on ;the daashboard to opperate it or if a bit on the posh side used a solenoid so the starter button was only carrying the small acuating current. As ar as I am aware Jowetts were the only buggers to 'play posh' by taking the starting current throught he push switch thus saving the cost of a solenoid.!

george

[Forumadmin]

The starter current on a post war machine is circa 500A. Would need to be more for a 6volt system or perhaps less because of low compression. Suggest you research on the web what is required for the starter that is fitted. Cable diameters for specific currents could also be found using Google. Note multicore cable is better than solid for carrying current.

[george garside]

sorry - missed a nought off!

george

[Peter Holden]

The outside dia of the original battery starter & earth leads was about 10mm. Standard starter cable is available from any good parts shop. You need to go to the trade type place rather than the high street chains that don't know what they sell! The nearest available size are:
196/0.40 cable with area of 25mm2 with an outside diameter of 9.8mm that takes 170amps or
315/0.40 cable with area of 40mm2 with an outside diameter of 11.8 that takes 300amps

For other wiring and deciding on cable sizes you need to work out the load on that cable. Use W = V x A to get the maximum ampage along any length of cable. If you refer to 'Vehicle Wiring Products' Web site, they are based in Ilkinton in Derbyshire they list all the available cables indicating the loads loads they will trake and also the normal use. Word of warning use different colours, you can trace where they go later. Also do not use to thick a wire as it will not go into the grub screw ternimals at the ignition switch and other locations.

[Tony Fearn]

Also do not use too thick a wire as it will not go into the grub screw terminals at the ignition switch and other locations.

The 1934 wiring diagram in one of my Gallery posts shows a number of wires going into and out of the ignition ports behind the PLC switch as Peter has mentioned.

I overcame this problem by soldering the several wires to a thick wire so that it went more easily into the grub screw terminal. I wrapped it in insulation tape of course.