Hi all. Another weird question. (Sorry!) I'm rewiring my '80 and this is my freshman attempt at such a project. I am not using a factory style harness as my project is going to be more in the vein of a 60's British sports car in the sense that it is stripped out and simplified as much as possible. I'm using a Jegs 21 circuit universal harness that is similar to a Painless harness.

I'd like to control the headlights, wipers, and cooling fans with relays rather than routing full current through the switches/thermostat. Additionally, I have a kit to replace the vacuum actuators with electric actuators (rotary style). The switch I'm looking at is a four position switch that goes OFF/PARK/LOW/HIGH. So how I'd like to do this is to run PARK -> relay to parking lights and gauge lights. Then LOW -> relay to headlight motors and low beams. Then HIGH -> relay to high beams. My question is I'm going to have a whole bunch of relay switches hanging out in the engine bay that will need to receive current from a source. My plan is to use the alternator hot as the high current source. Obviously I don't want to have 5 separate wires, and so the obvious solution to me is to construct some sort of junction where I can take a single think wire from the alternator to a junction point and then tap my high current supply from there.

Does anybody have any diagram for doing this, because I can't find one online. So either I'm looking at this the completely wrong way (in which case please correct me) or I'm looking in the wrong places. If I'm thinking about this the wrong way, would someone be so kind as to point me in the right direction? My background electrical understanding is that of electric guitars and their amplifiers, and those circuits are much higher voltage but low amp compared to automotive circuits. Thanks!

 

Watch out--you might wind up with an electrical system like came on '60s British sports cars--turn on the headlights and the wipers start running as you smell frying insulation and see little puffs of smoke coming from the dash

I can't see much need to use a relay for the parking lights as they draw very little current. Most of the parking lamps do double duty with the turn signals so you pretty much have to stick with the factory wiring scheme to get things to work properly.

The typical; way to use relays with the headlamps is to use the power coming from the switch to operate the relay coil. Locate the relays near the alternator and grab power directly from its output to power the actual lamps.

I also suggest you follow the factor scheme to power the dash lighting. Tap into the power for the parking lamps (when turned "on") and run it through another fuse (factory size is 3A) to power the dash lamps. This greatly reduces the possibility of that smoke from the dash thing should the finicky dash lighting develop a small short sufficient to blow the 3A fuse but not enough to blow the 20A for the park lights.

 

I'm not reusing any of the factory style components. The gauges are all Stewart Warner units and the literature that came with them says to daisy chain their power sources and the power source for the light bulbs (different circuits of course). So I was going to tie those into the parking lamps either way and solder an inline fuse or fusible link into the instrument panel lighting. I am going to have my column rebuild and the only electrical component in there is going to be the turn signal switch. The Jegs harness has the relays for the turn signals already installed and the signals are just connect the dots style wiring with it. But some of the stuff is left open to interpretation because it's a universal harness. My big question, again, is can I run a single high current lead from the alternator hot to a junction and then run the high current for all of the relays from this common junction? I will need such a tap for the headlight actuator relays (self contained using one wire from the headlight circuit to energize the relay), headlights, and wipers.

 

Forum member Richard 454 knows all of the answeers to your questions. Track hiim down. He helped me a lot. I did similar to what your plan is, I put a distribution box up front, than ran my relays to all the lights as needed, the elec headlight motors, the cooling fans, the trans cooler, etc.. By having that box up front ( below where the headlight actuators used to be) it made life really simple. Only needed to run the trigger wires from the cabin to the front and then the power was already there. I also used a circuit breaker to control the power line going to that box. And it was a lot easier and simple by doing a complete aftermarket harness as I did. Gotr mine from Ron Francis. Had every circuit I could need and then some in it.

 

Thanks! I will definitely look him up. I'm finding the same thing going through the Jegs harness - I was looking at what all I had last night and I realized that I'm just going to be heatshrink sealing some of the wires and deadheading them somewhere!

 

I realize you're not reusing the factory components but the there's much to be said for the general factory wiring scheme. The factory used two fusible links both of which are near the starter. On protects the starter, the other everything else.

Yes. Do remember that every passenger vehicle I've seen uses self-resetting thermal circuit breakers for headlamps and windshield wipers. The reason for this is these items are absolutely necessary when needed and you don't want a temporary problem to strand you for lack of a fuse or be tempted to use some non-fuse (screw, coin, foil, etc.) instead and risk damage/fire if the problem wasn't temporary.

Check with your state. I'm almost positive that emergency flashers are a required safety inspection item and if you won't be able to license the car if you intend to drive it on the street.

 

reegarding the hot lead off the alternator, the info I came across when wiring up my project is to think of the alternator as a faucet releasing current rather than water. The battery as a pool of current rather than water. If you run the lead off the alternator it will require a big load when called for, putting the alternator to it's limit. But if you run the lead from the pattery ( protected by a circuit breaker) the reserve current in the battery will absorb the spike without pulling it all from the alternator. Yes, the alternator will recharge the battery, but it won't be subject to the spikes directly. Not sure if I am explaining the theory clearly or not, or if it has any validity. Seemed like it to me, and most of the artlicles I came across thought so too, so that is how I did it. Just another thing to consider.

 

That makes sense! When I was learning about guitar stuff one of the books I read said to think of electricity like water and wiring as a plumbing system, with current being GPH and voltage being PSI in the "water" system. Then think of your components as "water wheels" which do work from the flow of the "water," so such analogies make sense to me.

 

Like I said... I'm not getting rid of the turn or hazard flashers. The only thing left on the column is the turn signals. The hazard flashers and horn are both going to be moved to the dash so that there is less wiring inside the steering column.

 

Here is what I used for my power windows. It's a 4 relay bank from msd. There is a single feed to four outputs and it can be either positive or negative trigger.

 

That's really nice! I'm going to look into that!