TR4/4A Ammeter Gauge TR4

[KVH]

Since I have a related post addressing the solenoid, I though I might ask:

What is the purpose of the heavy "Brown" wire from the ammeter gauge to the solenoid?

What would happen if that wire were disconnected?

Is that wire critical to the operation of the solenoid and starter, or is it merely current back to the gauge?

(I'm assuming that the basic operation of the solenoid comes from the ignition wire which is white and red, and the "case" of the solenoid being the ground--but would like to be educated)

 

[Geo Hahn]

I think that is essentially 'THE Wire' for the cars electrics.

For the ammeter to register current consumption everything has to flow thru it (other than the starter itself). You could leave the ammeter out by connecting its 2 wires but simply disconnecting it will leave you w/o electrics.

Thinking of electrics as plumbing (which I how I visualize it) the big black cable from the battery to the solenoid is the main power feed. At the solenoid it is connected to the brown wire which then goes on to power everything else going by way of the ammeter. After the ammeter comes the fuse block and then all the other stuff.

That white/red wire energizes the solenoid (switched by the key switch) to pass current from the big black cable from the battery to the big black cable to the starter.

 

[TR3driver]

As Geo says, the brown wire carries power from the battery to pretty much everything except the starter and the horns. That includes the ignition switch, which you correctly surmise powers the white/red to activate the solenoid. The solenoid is grounded through the case.