Good Method to Add Wiring For Add-Ons

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SpeedThrills

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My 74 Dart Sport, cloned into a 70-71 Duster has all the original wiring. It was a slant, it now has a 360, 727 (and a 9" Ford rear). The battery's going to be in the trunk with a shut off for the track. (I did that in another car, I'll be looking for help for this car in a separate post.)
What's a good way to wire:
-A fuel pump. (Relay?)
-Cooling fan (if it needs it).
-Line lock.
-Gauge lights.
-Oil pressure light. (Aftermarket)
-Tach.
-ATF temp gauge, Volt gauge (other gauges are mechanical)
-It has a mechanical water pump.
I think that's "all". I guessing some kind of switch panel with power taken from? It's a street-strip car. Mostly strip.
It runs, but I had it rigged temporarily. Other than the above wiring, it needs the battery set-up I mentioned, a fuel system, and a zillion other little things. I have a list, "Roadkill" stole my list idea. lol
 
Leash Electronics makes a really nice integrated street/strip panel.......I don't like the cheap and parts store quality of Painless and also Ron Francis. I f you want to step up even higher you can use Race Wire Solutions or Speedwire.
 
Search in here but also in the Racer's subforum for battery in trunk.
Some good posts in there from Cracked back and others. Some of the diagrams are confusing and I've redrawn those based on discussion with cracked back and 67dart273.
 
I'm going to mull this over for a bit. I'll only need one (fuel pump), maybe two (fan) switches. I can use toggles.
I think I'll just need a way to tap into what's there. Possibly a very simple fuse block.
Thanks for the ideas. I'll update.
 
Whatever you do make sure the load isn’t carried by the bulkhead connector or the ignition switch.
 
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Here's the threads with diagrams and photos for a couple of safe battery in trunk arrangements.
questions about battery disconnect wiring

Trunk Mount Battery - Wire Routing

Adding electric loads, especially equipment that will be running during start and while idling can cause problems with the original wiring strategy.
The original system only drew on the battery for starting and to keep things running for brief periods such as when at a stop light with wipers, heater, and lights on.
This post suggests two approaches when adding electric fuel pumps and fans.
 
Thanks, Mattax. I do get that I don't want to load anything excessively. But I certainly appreciate you being sure that I do! I will check out your links as I get into this.
 
Please don't put your fuel pump on a toggle. Put in an oil pressure switch, it'll cut power to the fuel pump if the engine doesn't have oil pressure.
If you're unconscious you are not gonna be able to flip that toggle off.
 
Please don't put your fuel pump on a toggle. Put in an oil pressure switch, it'll cut power to the fuel pump if the engine doesn't have oil pressure.
If you're unconscious you are not gonna be able to flip that toggle off.
I appreciate what you're saying. The toggle wouldn't be for safety, per se, it would be to make servicing easier. I.E., I could turn the pump off before I shut the engine off, to drain the bowls before a jet change.
The safety aspect will be covered by the "PUSH OFF" shut off switch on the back of the car, which is required, of course, because the battery will be in the trunk.
Thanks.
 
Pressure / thermo switches can be wired inline to work with toggle switches. I have my fans wired to 2 switches, one of the fans also has a thermo switch wired in to auto kick on if the switch is on or off. Check the rule book for the rules for wiring. Being our cars are pushing over 50 years. I’d replace all the wiring…
 
If you were adding more relays like say for headlamps and IGN power, I'd suggest installing a fuse/relay box from a later car. I used a 1990's Jeep one in my 3 Mopars, which gives 7 relays and many fuses, but a lot of work. I also used those to replace the factory starter and horn relays on the firewall to minimize clutter. Since you are only switching a fuel pump, stick with a single 30A Bosch relay. Cleanest are the type which have a weather-sealed base. Radiator fans might get by with a regular 30/40 Bosch relay, but most factory cars use a custom relay. I used the same solid-state PN as in my 1996 minivan which switches 2 hefty fans in parallel. It wires simply like a Bosch relay (2 control wires, 2 power wires). Don't make a mess of the wiring. Plan ahead. Many use split-loom, which is easy to modify if you need to add a wire. Cleaner is smooth plastic sheathing which you pull the wires thru, but doesn't work well if terminals already on them. Many use nylon mesh which can be expanded in diameter like a Chinese finger trap to fit over connectors, then pulled out for a clean small diameter. But, it can collect grub and is quite pricey. For wire passing hot exhaust pipes, you can buy "firesleeve" tubing of fiberglass insulation w/ silicone jacket.
 
So here’s what I’m thinking on adding circuits. I have this: Summit Racing SUM-900356 Summit Racing™ Fuse Blocks | Summit Racing
It’s for:
-tach
-oil pressure light
-volt gauge
-electric ATF temp gauge
-fuel pump (Holley blue)
-line lock
Research tells me that the last two draw 5 amps each, and the first four draw very little. I’m thinking 15 or 20 amps at the most, total, Probably 15. It need to be switched 12v.
I’m going to use a relay because from searching on here, I see that switched 12v is hard to come by. (74 low option Dart Sport). Do I tap into the blue field wire that also goes to the ignition, voltage regulator and ballast resistor? (to feed the relay 86 terminal)
I’ll fuse the 30 terminal, the one from the factory starter relay.
Here are my questions, as I’m not good with electricity:
Is this a good choice for a relay? Tyco / Bosch 30/20 Amp Relay – CE Auto Electric Supply
I have no idea how to select one. Amp rating? What does 30/20 mean, as an example. Oh wait, continuous open and continuous closed? Still, that confuses me. Specifically, what will I need? I know it needs to be NO (normally open).
Does it matter if there are two 87 terminals? Does that just leave an option on the table for another use?
@Mattax @67Dart273
 
I'm not going to be a lot of help right now, but the thing to test is whether relay will work close at say 9 volts when starting.
The line lock doesn't matter, but the fuel pump might matter depending on how much fuel is in the bowl.
160 mA @ 13.8VDC is pretty low. Lets say you use the run wire to trigger it. During start the battery gets drawn down to 10 or 11 Volts.
With the relay on the run side of the ballast resistor, there will be no more than .16 Amps going through the resistor.
change in V=I x R
change in V = .16 Amps x .5 ohms
change in V = .08 Volts.
So the relay will be powered by only a tenth of volt less than battery voltage during starting. So as far as that goes, ignition run circuit is probably OK.
Piggyback onto the ballast resistor or maybe there is an unused terminal from some feature on a '74 that you're not using. Choke assist? Idle stop solenoid, that sort of thing if you got rid of them.
 
I ordered this:
upload_2022-4-15_18-32-1.jpeg

I like the idea of finding a different power source. I know the wipers are available. They’re gone. Probably something else too.
 
I know '74 has a lot of differnces but I think Wipers are on an Accessory circuit.
I was assuming you wanted fuel pump on during start and run. Accessory will only be on with key in Run or accessory.
 
I’m thinking that the wipers won’t work on accessory, but the blower motor might. I’ll find out tomorrow.
I don’t want anything I’m adding to work on accessory, so I’ll go from there.
Other than test running the engine a couple years ago, this car hasn’t been used since 2008. I hooked up a battery today to start investigating as to what works. Nothing too tricky so far. It’s been sitting out in the garage so long, it’s fun trying out everything!
 
I found a female spade terminal on the outside of the firewall, where the wiring harness turns from along the firewall, and goes towards the starter relay.
I’m not using it, and it’s only hot with the key in run position. I’ll check the voltage on it before I use it. (For my add-on fuse block.)
Everything else is working except the dash lights. Good fuse, can’t find any juice and it’s a real pain getting my old self under the dash.
I thought the turn signals didn’t work. Turned out the flasher was verrrry slow to click. It didn’t like getting back into service. lol
Some of the parking light sockets were corroded, but they cleaned up.
 
I've done too many American Auto wire and hot rod wiring kits now that the next time I get into my duster I'm putting new wires in it. it's always satisfying and comes with tons of extra circuits...
 
Success!
I used the spade connector mentioned in post 18 to power the relay (switched 12v), the relay mentioned in post 24, and the fuse block mentioned in post 12. The unswitched 12v came from the starter relay.
I powered the fuel pump, line lock, atf temp gauge, volt gauge, oil pressure idiot light, and tach. All of the gauges and the tach are aftermarket.
Thanks for all the help.
Now to get the dash lights and dome light working…
 
Success!
I used the spade connector mentioned in post 18 to power the relay (switched 12v), the relay mentioned in post 24, and the fuse block mentioned in post 12. The unswitched 12v came from the starter relay.
I powered the fuel pump, line lock, atf temp gauge, volt gauge, oil pressure idiot light, and tach. All of the gauges and the tach are aftermarket.
Thanks for all the help.
Now to get the dash lights and dome light working…
This all worked well for a while. Now though, there’s no power at that spade connector I mentioned. The problem seems to have coincided with me welding on the car and forgetting to disconnect the battery first.
Anyhow, said spade connector is in the brake warning light circuit. Been checking continuity, I find it in that circuit. I can’t find the source for that current. Anyone have any ideas? I find continuity under the dash, near where the brake handle was, and in places throughout the harness out to the connector at the brake warning switch. I imagine I could find another source, but I’d like to know why this circuit went dead.
 
This all worked well for a while. Now though, there’s no power at that spade connector I mentioned. The problem seems to have coincided with me welding on the car and forgetting to disconnect the battery first.
Anyhow, said spade connector is in the brake warning light circuit. Been checking continuity, I find it in that circuit. I can’t find the source for that current. Anyone have any ideas? I find continuity under the dash, near where the brake handle was, and in places throughout the harness out to the connector at the brake warning switch. I imagine I could find another source, but I’d like to know why this circuit went dead.
We'ld need to know the connector cavity number or letter, or see its position, and then look in the '74 service manual.
 
From my 1974 service manual, it looks like that is cavity M with a 20ga black wire. Shows as the brake warning lamp wire. Fused from cavity six in the fuse block with a 3 amp fuse.

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