New Fuse Box and Relays

I was never very happy with the wiring in Tina. Much of it looked hap-hazard and suffered from what many cars of this age suffer from - loads of redundant wiring from additions made over the years, and then when those additions were removed, the wiring left behind. When I first bought her, I removed yards and yards of wire that was doing absolutely nothing.

While I was painting the engine bay, I wanted to sort out what was left. For example, I had an electric fan that was connected to the main fuse box (powered from the ignition switch) and would be pulling about 10 Amps. It was connected to the 35 Amp Lucas fuse, and then passed through two in-line 25 Amp fuses before reaching the fan. The fan thermo-switch was controlled off a sensor in the top hose, which I later converted to a thermo switch in the bottom hose.

I'd also heard stories from TR Register members about the lighting switch being a weak point (perhaps justified after 46 years) and that relays in the lighting circuit would be a worthwhile addition - would certainly save on the cost of repairs after a dashboard fire! I already had one modern relay in the engine bay to supply power to the air horns and wanted to hide it.

I'm also thinking of taking the load off the ignition switch for all accessories

Here is a picture of the wiring mess in the engine bay before I started.

I didn't want to add any relays into the engine bay, I wanted it to look reasonably original, and rather than use the old fashioned Lucas 6RA relays, I wanted to use the modern variety which are much smaller and therefore easier to hide somewhere. I obtained  second hand Lucas fusebox from the 60s/70s era that would hold 4 fuses (it came off a Rover P6) and decided to fit them into the passenger footwell.
I made a bracket out of a piece of steel, bent it in the vice to provide the right shape, and drilled 5 holes to accept a bank of five relays. I figure I'm going to use:
1. Air Horns
2. Main Beam
3. Dipped Beam
4. Accessory feed (take the load off the ignition switch)
5. Spare

I ran a brown wire (33 Amp) from the A1 terminal on the voltage regulator to the fuse box. The A1 terminal is the feed to the ignition switch, so this is permenantly live and is equivalent to taking the power off the back of the ignition switch. This feed will provide power to the fuse box for all permenantly live requirements (e.g. horn, electric fan).

I decided that as the headlamps were never originally fused, I would do the same and created a junction with bullet connectors to Tee off the power to the headlamps relays.

I bought plenty of wiring of the right colours from Vehicle Wiring Products and some PVC sleeving to thread the new wiring through so that it looked like part of the loom instead of creating another mess of exposed wiring running the length of the engine bay.

To connect the headlamps/main beam to the relays, this could be done in two ways - either find the wiring inside the car somewhere near the dip switch, or from the front of the car where the power wire splits into two to feed both headlamps. I decided to do the latter, which also seemed to be the common junction point for others that have done the same thing on the TR Register forum. I fed one PVC sleeve with 4 wires for the headlamps. Two of these would be an extension of the original power wires (main beam and dip beam) which would now form the switch power at the relay, and 2 wires which would now actually supply the power from the relay back to the main and dip beam.

To connect the electric fan and the air horns, I ran another 3 cables through another PVC sleeve. These were power to the air horns, "music" on/off wire for the air horns and the electric fan, each went to a fuse in the fuse box.

The PVC sleeves and their wires was pushed through the grommet on the nearside that also has the wiper motor wiring and connected up to the relays. Yes it does look like a bit of a spagetti mess, but I needed the wire tails to be long enough for me to reach into the passenger footwell with my crimpers - child labour is outlawed you know!

So after all that, I now have additional wiring in the engine bay that is very tidy, only one fuse for the electric fan instead of 3, and a much safer light switch on the dashboard. The new fuse box is now supplying the air horns, electric fan and my hazard warning lights (see other post)

With the help of a small block of wood and a piece of hardboard cut to shape to make a false bottom to the footwell, I only lose about 3 inches from the depth of the passenger footwell and everything is nicely hidden.

My next addition will be to take another live feed to a new relay which will be activated by a power feed from the auxillary power terminal on the ignition switch. The resulting output from the relay will feed the last 2 fuses on my new fuse box, and also fuse A3-A4 on the original fusebox in the engine bay. This will remove all current from the ignition switch and increase safety on the old dashboard switches. But I need to buy another relay for that one and so haven't got around to it yet. Once this modification is completed, I will alter the wiring for the radio and the air horns to use the auxiliary power, and move the 12 volt power socket from the original fuse box to the new one.

It's all very well making all these changes to the wiring loom, but unless it's all written down, you can guarentee that in a year or two, I'll have forgotten what I did. So I modified the original wiring diagram to reflect all these changes. All live additions are in blue, planned but not implemented changes are in green and wiring that will be decomissioned after changes are in red.

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