I have replaced the starter switch with a Tomaselli item which has one extra wire but I have sorted out the live and the earth I think. When I depress the starter swith the relay clicks but there is only a voltage of less than 4 volts reaching the solenoid, and then only intermitently. ( The starter and solenoid work ok. ) Does the relay just have one live feed, and if it is the relay that is faulty is there a commonly available replacement available ?
Any 40a normally open relay from Halfrauds will do.
Feed it from the bty+ve via a fuse , the other side goes to the start solonoid.Use the start switch to energise it.
A good way to test the system is to short the bty+ve on the starter itself to the solonoid +ve. If that turns the starter fine then it is either wiring or the start relay/switch.
Thanks kind sir.
Sir, bl##dy sir, I’ll have you know I could be trusted with a map. 
Oh, and you’re welcome.
As Mr Dunmore said any open relay should do, the one in my 1978 T3 is a 4 pin Valvar type 23 relay, made in Italy,
the black and white wire from the starter button goes to pin 85 in the starter relay,
ignition switch 50 is white, 30 is red, 15/54 brown and 16 green,
the top half of the rectifier is the ‘Live’ side, this side has two large spade connectors sticking out for the heavy duty red cables.
the bottom half is the ‘earth’ side which is where there should be a earth wire to the frame, do not connect this earth wire to the ‘live’ top half.
my T3 has just the 3 wires from the starter button, the two white and one black and white, some later models had four wires, the 4th being a black earth wire. but the fact that your starter relay clicks when pressed shows there is no problem with the starter button end.
what state is your battery in? needing a charge ? I would first of all check the tightness of the battery connections, a loose connection might just about spin the starter but not at the rate required. to start the motor.
Thank you also, most helpful.
I agree.
what state is your battery in? needing a charge ? I would first of all check the tightness of the battery connections, a loose connection might just about spin the starter but not at the rate required. to start the motor.
Ah yes are we guilty of assumptions ~ viz, battery is OK ~ 4 Volts could well be all that a discharged battery will manage ~ note just checking the Voltage of a battery, with no test load to go with it, is no indication of it’s state of charge and it will still look good to go.
HTH
All soted. I think the key was taling the live feed direct from the battery. Onwards and upwards.
Ah the click-no-start cause and remedy proved once again.
