Electrical advice needed

[Whisler]

I am assembling a fuse/relay board for future electrical additions. It will contain a 4 position bus bar (proper term?) with a common positive and individual fuses for:
1. Electric choke pulled in by the stator wire to relay.
2. Auxiliary backup lights with switch to relay.
3. Driving lights with switch to relay.
4. Clearance lights pulled in by headlight switch to relay.

I am using a common ground for all 4 relays connected to the battery negative. What size wire would be appropriate for this ground? Would 12 gauge wire suffice?

Will 14 gauge wire suffice for the accessory to relay? Also what is the best way to tie in to the stator wire? I don't want to use a t-tap. A friend suggested what he call a "Western Union" connection: skin the stator wire, wrap the new wire around it solder and tape. Does this sound right?

All help appreciated as I am have been called a "smart aleck" but never a smart elec-trician.

[Gary Lewis]

Why do you need to "tie into" the stator wire.  Is that circuit, the white/black wire, being used?  I know the 5.8L HO had a choke relay pulled in by the stator voltage, as shown here (https://www.wirebarn.com/Wire-Calculator-_ep_41.html), but if you have that then you won't need your own relay.  Right?

As for a ground for the relays, assuming that the relays are supplying voltage to the circuits, all the ground circuit will carry is the coil current, and that's less than an amp for a Bosch relay.  So 4 relays can't be pulling more than 4 amps, and this site says 16 ga wire would be good for a 17' run with only a 2% drop in voltage.  In other words, it would be overkill.

But I'm not sure what you mean by "accessory to relay".  Can you ask that one again?

And bus bar is the right term.

[NotEnoughTrucks]

The only current flowing to ground looks to be relay coils and this is not going to be a large current. 12 ga would be overkill. 14 ga would be plenty.

Ampacity charts can be helpful in determining wire size. Here's one.

https://www.engineeringtoolbox.com/wire-gauges-d_419.html

I'm not sure what you intend with accessory to relay, but if you are referring to the switched circuits, they should be appropriate for your intended load. If in doubt, heavier gauge wiring will always minimize voltage drop.

As to that stator connection, the skin, wrap, solder and tape process sounds appropriate.

[NotEnoughTrucks]

And Gary beat me to it!

[Gary Lewis]

Yes, but not by much.  And even then my link to the ampacity calculator was the wrong one - now fixed.

Anyway, we seem to think alike.  I think that's good for me, but maybe not for you.  

[Whisler]

What I meant by "accessory to relay" is the power wire from the relay to the accessory, in this instance the various lights and choke. Now that the link has been posted, I should be able to look up the amp draw of the various lights and go from there.

I just wasn't sure about the ground wire.

As for the stator connection, this is an '89 truck converted as per my signature. There is no choke wire and has been converted to 3G alternator, so a wire connects the large lug on the alternator to the stator plug and is only about 6 inches long. This is the wire that I will have to tie into so as to use the stator signal to trigger the choke on the Edelbrock carb.

I hope this clears up the muddy waters.

Thanks for the info so far.

[Gary Lewis]

Ahhh!  That makes sense.  Yes, look up the current draw of the accessory and then use the appropriate wire size.  And, when in doubt go bigger.  And, be sure to fuse the feed to each relay appropriate to the size of wire.

As for the stator wire, now I understand.  If you use adhesive-lined shrink tubing you can strip a section of the existing wire, wrap the new wire around that several turns, solder it, and then cover it with the shrink tubing.  The adhesive lining will flow into the cracks and crevices and seal even when you have two wires on one side and one on the other.

[Whisler]

Thanks for the help. Greatly appreciated!

The bus bar I am using has a common hot terminal and 4 positions for circuits, each one with a fuse plug between the common hot and the circuit connection. This bus bar is intended for marine engine compartment use and the relays are waterproof so should be fine for engine compartment mount near the battery.
Now I can just figure the load on each circuit, choose the appropriate wire size and fuse size and go from there.

Thanks again

[Steve83]

Whisler wrote

...for future electrical additions.

To properly size the wire & fuses, you have to KNOW the current draw of each addition.  To size it for unknowns, you'd have to go big, or limit your future additions to the wire size you build this with.  IMO, it's easier to just wait for a need, and then build to that.

Whisler wrote

...bus bar (proper term?)...

The bus bar is the actual metal strip that joins several circuits.





The whole assembly with fuse holders, binding posts, mounting holes, & accessory terminals is a "4-position accessory fuse block".

Whisler wrote

1. Electric choke pulled in by the stator wire to relay.
2. Auxiliary backup lights with switch to relay.
3. Driving lights with switch to relay.
4. Clearance lights pulled in by headlight switch to relay.

Ford direct-powered most of those, so with modern LEDs, it's not really necessary to use relays for them.

Whisler wrote

I am using a common ground for all 4 relays connected to the battery negative. What size wire would be appropriate for this ground?

Add all the current that will potentially pass through the wire, and choose the gauge based on the length of wire & its environment (temperature).

Whisler wrote

Will 14 gauge wire suffice for the accessory to relay?

Depends on how much current the accessory draws, what heat sources it passes near, and the total length of the wire.  The chart at the bottom R of this table is from Ford, but there are others linked in the caption:

Whisler wrote

...what is the best way to tie in to the stator wire?

I'd pull one of its terminals out of a connector shell, and solder the new wire to it.  Then put the terminal back into the connector, and you're done.



...but keep reading...

Whisler wrote

I don't want to use a t-tap.

Good.  ScotchLok taps are probably the WORST way to splice a wire yet created.  Never ever use them for anything.

Whisler wrote

...skin the stator wire, wrap the new wire around it solder and tape.

I call that a "pierce splice", and it's a really-good way to tap a wire without compromising the original wire's integrity (no potential for a new break or high resistance in the original wire).

NotEnoughTrucks wrote

...heavier gauge wiring will always minimize voltage drop.

But it's harder to bend, which can make routing & terminating it much more difficult.  Besides: the main consideration should be overheating the wire; not low voltage to the load.

Whisler wrote

...3G alternator, so a wire connects the large lug on the alternator to the stator plug and is only about 6 inches long.

The 3-pin connector is for the voltage regulator, which is the one (Y wire) that connects to the output; the 1-pin (Bk/Wh wire) is the stator.

Whisler wrote

...use the stator signal to trigger the choke on the Edelbrock carb.

That doesn't sound right to me.  The last Edelbrock carb I remember installing used a 12V choke heater.  The stator is used for factory carbs because they use the older 6V choke heaters, and the stator output is roughly 1/2 the alternator output.  But it's also AC (because it comes directly off the stator windings); not DC (through the diodes).

So not only will you be trying to trigger a DC relay with AC; you'll be tapping a ~6V circuit to drive a relay to step up to 12V; when you could simply tie the choke heater directly to a key-switched 12V circuit (assuming your heater is 12V - read the manual).  I like to tap the fuel pump relay output because it's only hot when the engine is actually running, and it can handle some extra current.

Gary Lewis wrote

...strip a section of the existing wire...and then cover it with the shrink tubing.

A tube that fits over the stator connector won't shrink down onto the wire (or even 2).  Even if he removes the connector shell, the metal terminal inside is still pretty large.  To use shrink tubing, the wire generally has to be cut.

[Gary Lewis]

Steve - The 5.8 HO's, and probably the 7.5L's, used a relay pulled in by the stator current, as shown here in the 1986 EVTM: http://www.garysgaragemahal.com/carburetor-circuits.html.  And I'm running a Bosch relay pulled in by the stator wire on Big Blue to power the choke on the Edelbrock.  Both the Holley 4180C and the Edelbrocks have 12v heaters, and this approach works quite well.

But I do agree that insulation-displacement connectors should never be used - on anything, anywhere, anytime.  In fact, I think I know the final resting place of the person that invented them.  

[Whisler]

Steve and Gary: thanks for the info. Steve when I said "future" I meant immediate future which may not have been clear. I have everything but the driving lights, so as soon as I pick these up and select a mounting position I will be ready to go...into the future.

I read about the choke heater relay deal on FTE at some point, where it was stated that this route or a connection to an oil pressure switch of some sort was a good way to avoid heating up the choke by having the key on when the engine was not running. Yes, Edelbrock choke heaters are 12 volt.

As for the tap-in to the stator wire, I think a pierce or wrap solder connection coated with "liquid electrical tape" (vinyl solution) should work, maybe even reinforced with tape. I was remembering the 3G wiring incorrectly, I think, but I knew that the stator wire was just a short loop to the stator connector because I had to buy and install the stator connector. I remember it was a pain to solder that loop wire to the short stator connector wire.

Thanks to all for taking the time to help a guy out.    

[Rembrant]

Just to throw it into the mix, I'm running the electric choke on my new Holley 4160 directly off the stator...same wire that fed the Ford choke. I have no idea if this is OK to do on the Edelbrock carb, but in my research, I found that all kinds of people use the Ford wire to feed Holley carbs.

Mine seems to work fine that way.

I didn't save the link unfortunately, but I found a thread on another forum where a guy actually tested and compared choke supply voltages, and claimed that the 6v supply didn't make much difference at all...maybe a few seconds.

[NotEnoughTrucks]

The truck in my profile pic, AKA the War Wagon ran an Edelbrock carb and the choke heater was powered off the stator. Worked, sort of. The choke pulled off reasonably quickly, but I had to adjust it from the factory setting. The truck did have starting issues, but not because of the choke. Fuel seemed to drain back, or otherwise empty the bowl if the truck sat a few days and hot starts were always accompanied by a wide open throttle as the fuel seemed to boil over. I have been told this may be due to the Edelbrock not liking higher inlet pressures and even the mechanical pump on that previously carbureted 351W was capable of overwhelming the needle and seat.

Speaking of fuel pumps, if you are using an electric pump, that voltage must shut off when the engine is not running, even with the key on. If you are one of those misguided souls who downgraded your EFI equipped vehicle to a carburetor, that ability to control your fuel pump was lost with the ECM. I prefer to use a relay triggered by both a "live on ignition circuit" to the positive side of the coil as well as an oil pressure switch which grounds the negative side of the relay coil. Late model Ford applications with that glorified idiot light masquerading as a real gauge have the right type of sender for this. An honest idiot light works the opposite, grounding when oil pressure is lost, I feed voltage from the crank switch to the backside, (NC) of the relay contacts, use the common contact to feed the pump and the NO side of the relay contacts for a fused battery feed with appropriately sized wiring.

On appropriate sized wiring, I'll agree with Steve that larger wiring can bring some routing and terminating challenges. Trick here is to use common sense. I would think that lost voltage always ends up as heat although I can relate to using some ridiculously oversized wires in a voltage sensing application back in my RR signalling days. Even with low currents, sometimes you can measure the difference although I cannot think of any automotive applications where such measures would be warranted.

[Whisler]

"If you are one of those misguided souls who downgraded your EFI equipped vehicle to a carburetor"

Yes I am afraid I am one of those. The '84 F150 that I owned had a rebuilt 351W carbed engine and a rotted frame. The '89 F250 I acquired cheap had an EFI 302 that leaked oil like a sieve and a 5 speed trans. with lousy gearing (not too good for my old knees), but a good frame. I don't regret the swap at all. I now have a good running truck that actually performs better than the EFI equipped one.

[Steve83]

Gary Lewis wrote

The 5.8 HO's, and probably the 7.5L's, used a relay pulled in by the stator current...

I don't doubt it.  But it would be simpler, cheaper, & more-reliable to just direct-wire the (12V) choke heater to a key-switched or engine-running-only 12V circuit.

[85lebaront2]

If you want to do that, use a Chrysler carbureted 2.2L Choke switch, they are a NO oil pressure switch with two terminals, no need for a relay, just fuse it.