Wiring Accessory Relay Panel into Classic Car - Questions..

[1974_Saab_Sonett_Project]

Hi Everyone,

New to the forum but hoping I can find a little help with my restoration project...

I am adding a secondary wiring "system" to my project car (username) to control add-on systems to include an electric fuel pump, electric radiator fan, fog lights and also to replace/upgrade the original wiring system for the factory ignition, headlights and accessories such as radio, interior lights and gauges.

I am starting with a TruMods Relay block and fuse kit which will be powered through a battery shutoff switch from the battery connected to a bus bar to feed the 6 fused relays (I am thinking that having a dedicated shutoff to my accessories would be beneficial. Power will still run from battery straight to starter/alternator for direct charging and connection). Grounds will connect to another bus bar to chassis ground and all components mounted to a sheet of 1/4" thick ABS plastic.

Here is where I have questions...

1. Should my #87 feed wires from the relays go through a Blue Sea Systems 5035 ST Blade fuse block? (This was my plan - but I can't figure out if this is necessary. Do these feeds need to be fused? Or just connect through a terminal strip block straight to the device?)

2. My TruMods kit says the #86 switch wire to the relay should be fused - should I wire the Blue Sea 5035 fuse block from these feed wires? If so, should they be fused through the #86 feeds to the relays, or should they be fused on the other side at the power feeds to my switches? I plan to use mostly positive switching ILO ground switching.

It seems like I should fuse all 3 positive runs but this seems excessive (i.e. 1: battery > fuses > #30 relay power as wired in the relay block. 2: #87 from relay > fuse > device. 3: #86 fused from switch into relay (or power to switch fused before switch and no fuse from switch through #86 into relay?)

This is my first deep dive into building automotive circuits and am learning everyday so I appreciate in advance any advice or suggestions.

Attached is just a preliminary mock-up of me brainstorming for reference. I will be adding in terminal strip blocks and using a larger ABS plastic to mount everything. In the picture, 86 switch is white, 87 device feed is blue and 87a is yellow (most likely not used unless for indicator lights).

Thanks!

 

[1974_Saab_Sonett_Project]

To simplify the question, where does everyone fuse their circuits? Any input would be greatly appreciated!

 

[brianmoooore]

The connections from the 87s should be fused at the appropriate rating for what they are feeding and the gauge of wire used.
The feed(s) to the switches should also be fused, if you are using positive switching. These fuses wouldn't be required with ground switching.
The common feed to the 30s should also ideally be fused at the battery end, unless the run is short and well protected against damage.

 

[1974_Saab_Sonett_Project]

The connections from the 87s should be fused at the appropriate rating for what they are feeding and the gauge of wire used.
The feed(s) to the switches should also be fused, if you are using positive switching. These fuses wouldn't be required with ground switching.
The common feed to the 30s should also ideally be fused at the battery end, unless the run is short and well protected against damage.

Thank you very much for the reply, that all makes sense.

Do you see any issue if I fuse the 87s back at my relay panel which will be in the trunk, or should they be closer to the device? Or does that part matter?

Thank you!

 

[brianmoooore]

87s should be fused close to the relays.

 

[1974_Saab_Sonett_Project]

87s should be fused close to the relays.

Perfect! That fits my plans really well.

Would you say the feeds to the switches can also be fused back towards my relays or should they be closer to the actual switches?

Appreciate all of the guidance!

 

[brianmoooore]

The fuses for everything should be as close as possible to where the power is coming from, so the fuses for the switches should be in the permanent live wire to the switches, and at the other end of that wire from the switches.

 

[1974_Saab_Sonett_Project]

The fuses for everything should be as close as possible to where the power is coming from, so the fuses for the switches should be in the permanent live wire to the switches, and at the other end of that wire from the switches.

Thank you, so do I need to fuse both sides of my switches? One fuse on the live feed to the switch, and one fuse on the output of the switch on the way to the relay?

 

[brianmoooore]

No need for a fuse between the switch output and the relay, just the ones in the live feed to the switch and the 87 outputs from the relays.
If you 'ground switch' - connect 30 and 86 together at the relay, and fit the switch between 85 and ground, the switch fuses won't be required. Also has the advantage of less 'live' wires running through the car.

 

[1974_Saab_Sonett_Project]

Small update- here's what I have planned so far... I'm waiting on a continuous solenoid to fit in the blank spot in the picture attached.

The plan would be for the panel to be turned on with the ignition switch in ACC triggering the solenoid; power in from my shutoff switch through the breaker and power out of the solenoid to the power bus bar.

Bus bar would feed my relay box and my switches fuse block.

Power from breaker would also feed a small fuse block for fused accessories and also power to ignition switch.

Device feeds on through their own fuse block on the left.

I hope this layout also gives me some flexibility to run a few ground switches and to reconfigure some of the relays.

Any criticism or feedback is welcome, I've got two thirds of the components mounted to the panel and I'm hoping I'm on the right track!

Quick and crude diagram attached too..

 

[1974_Saab_Sonett_Project]

My solenoid came in, got everything mocked up a little better and ordered a new breaker switch with larger stud size and started practicing with making wire. Slow progress but I'm liking how it's progressing!

 

[1974_Saab_Sonett_Project]

Today's progress and happy with the results so far. I'm trying to keep the wiring as clean and organized as possible. Takes a lot longer than I thought!

 

[1974_Saab_Sonett_Project]

I decided to change the bottom of the board with a larger bus bar for both my grounds and my relay switches (86), very happy with it. The yellow 87a's are still TBD.

Waiting for my new breaker then I'll mount and wire the solenoid and small fuse block up top, getting closer!

 

[diditrain]

Looks very neat and organised.

 

[1974_Saab_Sonett_Project]

Looks very neat and organised.

Thank you, I appreciate it!