Firstly, Thanks to everyone, especially Doug for their invaluable advice and information on all the questions I've asked. Now for one more!
Just rewired the entire headlamp system, from the headlamp fuse box to the headlamps themselves.

Fuse box is replaced for one using modern/standard 5 Amp "blade" style fuses. The new box is fed from the Headlamp main relay just as the original one did. The new fuse box only supplies trigger signals to 4 relays (two per side) - mounted on each side of the radiator shroud support. The original fusebox (less relays) would send power for the headlights through the headlamp switch and puny 16 G wires)
One set of relays trigger LH Low beam (Relay # 1) and the other the LH High beams (Relay # 2).

The other two relays (Relays #3 and #4) likewise trigger the RH side. Therefore, the current draw through the headlamp switch is now very low

Main power to each relay output line is provided by a 10G "bus" type feed wire from the RH bulkhead "+" terminal adjacent to the battery. An in-line 40 Amp fuse protects this wire feed.

14G wires run from each relay to each headlamp (High beam relay feeds two lamps).

Headlamps are now Hella "Conversion" units

(My Hella Lights :: Vision Plus 5¾" Conversion Headlamp).

Works great and substantially more illumination. Now will need to adjust the beam patterns.

My question is how does the "Latching" feature function on the main headlamp relay, and what is the purpose of the pigtailed capacitor?

Don't have a camera but when I do I'll post some pictures.

 

The mechanism is 100% mechanical. If you open up the relay you will see that there is a cam arrangement which latches the relay in one or the other position to provide a toggle effect.

 

"...what is the purpose of the pigtailed capacitor?"

I am going back decades into my old electro mechanical telephone system training. A capacitor makes a relay slow to release. So when you pulse the relay to change hi/lo beam the relay will operate and instead of releasing immediately it will hold operated for a brief period (depending on capacitor size and coil resistance).



I think this may be part of design to ensure the relay operates fully and momentarily holds so it fully actuates the cam mechanism to do the changeover. It will operate without it but may become flakey and prone to partial operation.

 

Really? They always told me it kept the points from arcing, and thus greatly slowing eventual burning away; which concept I completely understand.

This is a whole new wrinkle. It will take some time to wrap my brain around it.
(';')

 

Correct for the ignition, I thought he was talking about the capacitor that sits across the headlight relay. In that case its across the relay coil and doesnt help the contacts.

Similar idea really, when the ignition coil field collapses the capacitor absorbs the energy. If its put across a relay coil it will hold the relay up for a short period as its stored energy discharges once power is removed.

 

Thanks Steve, one day I will have to open one up!

 

Sounds like you made a great improvement to your cars lighting.
I did a similar install using Eaton's relay/fuse box as age was reducing the brightness of my headlights each year.

I wired it to my Aux battery instead, doing a 4ga to 10ga distribution. The whole switch now fed from the relay's low level signals. I was told it wasn't designed to handle such high amp sources.

I can now installed those HELLA H4 130/90W for those unlit back roads I like to travel on at night. I finally got rid of the old fuse box sitting on the fender as it no longer had a purpose.