Looking for wiring advice with accessories

[Jonathan D]

I’m looking for some guidance on wiring as it’s certainly not my strength. My carb build is basic but when I consider my addons I’m still trying to determine how to power everything in a simple yet safe manner. Then there is the topic of when to use relays??

I have the Ron Frances harness, carbureted with a mech pump so I believe I have at least 3 circuits (radio, fuel pump, EFI) in the harness that I can use to switch a few extras?
1. Does the RF harness have a relay for the fuel pump? If yes, what would be the recommended use for that circuit based on my options?
2. I’m using a mini starter so am I correct is saying there is no need for an extra solenoid?
3. I have the front mount Breeze Box and I purchased the heavy master cutoff switch from Factory Five but I’m on the fence about using it. I was thinking if I use it, I could probably feed my relays at the dash from it but what about fuses? Is there a clean way to protect those circuits?
4. Seat heaters – I have the warmseats from Mike Forte, they include relays and switches but again I’m looking for advice on where to pull the power for the relays and switches.
5. Reverse Lights – since this needs to be hot whenever the car is running could I use the radio circuit for this and use the reverse switch on my T5 to switch the circuit ….on the ground side?
6. Wipers - Is there anything extra with wiring that is not already laid out in the manual?
7. Heater – Same question here, do I need to plan anything extra?
8. USB charge ports for cell phones, is that EFI/Crank circuit ok to use for something like this with or without a relay?

If anyone has a build page that has lots of details on wiring that would be great to have as well.
Thanks guys

[edwardb]

My responses:

1. Yes, the fuel pump circuit has a relay. The ground leg for the relay goes through an inertia switch, which you don't need. So you could remove the inertia switch, tie the two wires to it together, and the relay would always switch on with the ignition and you would have a powered circuit.

2. Correct.

3. Not quite understanding this one. Relays at the dash? What circuits are you trying to protect? All the other circuits you describe are using circuits from the RF harness which have fuses on each already.

4. Don't get lost in the relays, etc. for the seat heaters. The seat heater harnesses have a ground and power lead. Just need to get those wired. Maybe the fuel pump circuit? Although it has more capacity than actually needed.

5. Yes, you could use the radio circuit. Although if you use LED backup light(s), the current draw will be very low so could technically be shared with something else if together not too much current. I've switched the +12V side when I've done backup lights. Then all the lights in the back, including the backup light(s), are grounded in place.

6. There are separate wiring instructions you have should for the power and switch. Needs to be correct so it gets both speeds and the park function.

7. Shouldn't be anything extra if you're using the RF heater circuit.

8. The EFI/Crank circuit has plenty of power for a USB charge port. Not need for a relay.

Everybody tends to put their own spin on wiring. I'm not aware of any single build page. I'd review as many as you can and pick up ideas.

[scrubs]

I completed my car with a pretty bare bones build. Will give you my fetal thoughts...

4. I would use circuits you did not use....e.g. I added a USB charger for my wife using the wiper circuit.
5. I think you would be fine with anything that works with the key on..,so ACC on beyond.


I am adding a USB charger as I type....my assumption is that if the circuit supports the amp draw, your good to go. Use whatever excess wires are available to power whatever as long as the amps at the fuses/circuit will tolerate it.

You can generate a ground wherever.

j

[maclonchas]

I think following edWardB and Scrubs advice is probable the safer and easier method for your electrical wiring. I was not happy with the additional relays needed as I added EFI, seat heaters and other relays for my build and wanted better access than crawling inside the DS footbox or behind the dash to do troubleshooting or replacement. I ended up ordering on Amazon this relay and fuse box https://www.amazon.com/dp/B0CDZCKBWM?ref=ppx_yo2ov_dt_b_product_details&th=1). I placed this box engine side on top of the PS footbox and placed my positive bus bar engine side near the relay box. This allowed me to centralize a lot of my additions and changes to the wiring and kept me from worrying about possible overloads and having dedicated circuits for these subsystems. I could have reused more from the RF harness, but I wanted to document well the wiring changes made outside of the RF wiring diagrams without having to redraw those diagrams and remember what I had done for that circuit. I keep all those extra diagrams in my build notebook and that keeps me organized

Relay Box
192093

Bus Bar with Alternator Fuse
192095

I would use whatever method you fill comfortable with and works for you to stay organized.

Hope this helps

Bill

[Jonathan D]

My responses:

1. Yes, the fuel pump circuit has a relay. The ground leg for the relay goes through an inertia switch, which you don't need. So you could remove the inertia switch, tie the two wires to it together, and the relay would always switch on with the ignition and you would have a powered circuit.

2. Correct.

3. Not quite understanding this one. Relays at the dash? What circuits are you trying to protect? All the other circuits you describe are using circuits from the RF harness which have fuses on each already.

4. Don't get lost in the relays, etc. for the seat heaters. The seat heater harnesses have a ground and power lead. Just need to get those wired. Maybe the fuel pump circuit? Although it has more capacity than actually needed.

5. Yes, you could use the radio circuit. Although if you use LED backup light(s), the current draw will be very low so could technically be shared with something else if together not too much current. I've switched the +12V side when I've done backup lights. Then all the lights in the back, including the backup light(s), are grounded in place.

6. There are separate wiring instructions you have should for the power and switch. Needs to be correct so it gets both speeds and the park function.

7. Shouldn't be anything extra if you're using the RF heater circuit.

8. The EFI/Crank circuit has plenty of power for a USB charge port. Not need for a relay.

Everybody tends to put their own spin on wiring. I'm not aware of any single build page. I'd review as many as you can and pick up ideas.

edwardb...thanks so much for taking the time to provide detailed responses! I have read many of your posts and have been learning alot from the tips you have given others. I'm feeling much more confident on the wiring plan and I think you are saying nothing I have needs any extra relays? (besides the ones included in my seat heaters) On point 3 I mentioned "relays at the dash"...I was just thinking I needed to add extra relays behind the dash to power some of these other items. I'm happy to hear I already have all I need in the ron frances harness. I can get the label maker out and label curcuits I'm repurposing and make some wiring plans that show how they are being used. I really prefer that over adding even more curcuits to the car.

[Jonathan D]

Thanks scrubs and maclonchas, I really like the idea of using the basics that came with the car

[edwardb]

edwardb...thanks so much for taking the time to provide detailed responses! I have read many of your posts and have been learning alot from the tips you have given others. I'm feeling much more confident on the wiring plan and I think you are saying nothing I have needs any extra relays? (besides the ones included in my seat heaters) On point 3 I mentioned "relays at the dash"...I was just thinking I needed to add extra relays behind the dash to power some of these other items. I'm happy to hear I already have all I need in the ron frances harness. I can get the label maker out and label curcuits I'm repurposing and make some wiring plans that show how they are being used. I really prefer that over adding even more curcuits to the car.

You're welcome however I was able to help. Keep in mind, the most common reason for an automotive relay is to enable a low amperage circuit to switch on or off a higher amperage circuit. Example is the seat heaters. The heating elements draw (estimated) 8-10 amps. But the small on/off switches probably only handle a couple amps, if that. So the on/off switches are used to trigger a small coil in the relay that opens and closes contacts that can handle the current of the heating elements. The fuel pump and cooling fan are other common examples. Not to be confused with fuses in the panel that are there to prevent overloading the overall circuit, melting the wires, even starting a fire in the worst case. So as you're thinking about adding circuits, be aware of the current the circuit draws. Plus whatever is going to switch the circuit on and off. If the circuit draw exceeds the rating of the switch, then a relay is appropriate. An EE (I'm not one...) I'm sure would recommend some margin of error. Hope that makes sense.

[Jonathan D]

You're welcome however I was able to help. Keep in mind, the most common reason for an automotive relay is to enable a low amperage circuit to switch on or off a higher amperage circuit. Example is the seat heaters. The heating elements draw (estimated) 8-10 amps. But the small on/off switches probably only handle a couple amps, if that. So the on/off switches are used to trigger a small coil in the relay that opens and closes contacts that can handle the current of the heating elements. The fuel pump and cooling fan are other common examples. Not to be confused with fuses in the panel that are there to prevent overloading the overall circuit, melting the wires, even starting a fire in the worst case. So as you're thinking about adding circuits, be aware of the current the circuit draws. Plus whatever is going to switch the circuit on and off. If the circuit draw exceeds the rating of the switch, then a relay is appropriate. An EE (I'm not one...) I'm sure would recommend some margin of error. Hope that makes sense.

Makes sense, thanks again!

[F500guy]

Not sure yet how my set up will be placed in the car, but I had to many accessories to tap off the unused portion of the RF harness. I had the following extra that needed power and I did not want any fuses in the harness:
1) EPS-40 amp and an ignition-on low power ckt
2) Electric Parking Brakes-40 amp and ignition-on low power ckt
3) Rear courtesy light in the trunk
4)Ckt for back up lights
5) Seat heaters

I purchased a little fuse 3 ckt fused distribution board with midi fuses to feed the 40 amp parking brake and EPS and a relay board from Painless that has 7 20 amp fuses that will be ignition on. Not doing the lay out until winter time, so I have no pictures yet of the install.

192131192132

[Jonathan D]

Not sure yet how my set up will be placed in the car, but I had to many accessories to tap off the unused portion of the RF harness. I had the following extra that needed power and I did not want any fuses in the harness:
1) EPS-40 amp and an ignition-on low power ckt
2) Electric Parking Brakes-40 amp and ignition-on low power ckt
3) Rear courtesy light in the trunk
4)Ckt for back up lights
5) Seat heaters

I purchased a little fuse 3 ckt fused distribution board with midi fuses to feed the 40 amp parking brake and EPS and a relay board from Painless that has 7 20 amp fuses that will be ignition on. Not doing the lay out until winter time, so I have no pictures yet of the install.

192131192132

Looks good!