As long as the catastrophe occurs on line 1 or 2 I still have lights, a short to ground occurring on 3,4,5 or 6 blows the control circuit fuse and takes it all out.

_________________
1960 Seneca 225 turbo soon to be EFI

I don't think you've made a wise decision. I think "my" way is not only safer but also functionally better. I think your newness to this sort of work means you ought to listen to those who've done it before. But it's your car and your decision and I wish you the best of "luck" with it.

*shrug* :shrug:

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

This is a diagram I threw together months back when I was playing with the expresspcb program. You only lose the whole circuit if the fuse before the switch goes, but that fuse doesn't have much of a load on it with the relays in place. I did not include the standard relay numbers but I should have and I am not sure if the song chuan relay that my box uses has those designations anyways.



Wire "MF" is the main feed going to the underhood fusebox which is the location for all fuses and relays in the diagram. The full size copy of the diagram has a legend in it that includes what each wire goes to and from, but it made the picture too big to easily post

My decision is to see if I have a relay position left over when I'm finished with the rest of the car.
The line diagram and related commentary depicts "your" suggestion. Even if I use a third relay for the dash and tail, the control circuit is a weak link that can take out all the lights.

_________________
1960 Seneca 225 turbo soon to be EFI

Mcnoople your drawing and the one I posted are identical, though I neglected to draw the high beam selector switch. Now add dash and tail lights.

_________________
1960 Seneca 225 turbo soon to be EFI

This is how I wired my headlight circuit:



Total connected load (Hi and Lo beams) 12 amps. Well below the rated switching capacity of the relay, the interrupting rating of the fuse and the current carrying capacity of the conductor.

The control circuit would be the same no matter how many relays I use.

Using a relay for dash and tail is overkill, since I am now interrupting less than 10 amps on a switch rated at 30.

As I stated "The redundancy would certainly be better but not "far and away" better."

"I think your newness to this sort of work means you ought to listen to those who've done it before." Quite a condescending remark.

_________________
1960 Seneca 225 turbo soon to be EFI

If you throw out ideas on a forum, be prepared for others who don't agree with your ideas. Dan IS something of an expert when it comes to automotive lighting. I look at your layout & see a couple points to consider.

Hi beams run in addition to lows. If you run hi beams for any length of time, you might overheat the ground connection at the bulb- I've seen it happen.

As Dan stated, a single fuse for the headlights gives no redundancy. Most modern cars have 4 separate fuses- one for each hi & low beam.

The big thing is there is no seperate fuse for the dash or tail lights. A short in any of those areas will take out ALL lights.

_________________
63 Valiant Wagon
225 - 4 bbl

Oh, dear me. Did I hurt your feelings? I'm so sorry, I didn't mean to do that. It's my fault, really; I misunderstood you. When you said "I have been intimidated by automotive electrical systems for long enough", I took that to mean you have little or no experience with this kind of thing, and were posting here to get advice from those who know more than you about the subject. Evidently your lack of knowledge and inexperience with wiring is a sore subject for you ("quite a condescending remark", you say); you want to think of yourself -- and you want us to think of you -- as an expert. Okeh, »POOF!« you're an expert; you know everything there is to know.

I would ask that in future, Ken, you take my remarks in context -- for example, look and remind yourself that "I think you ought to listen to those who've done it before" was followed by "it's your car and your decision" -- but it's not important; I won't be troubling you with advice in future.

User KenUSA is <IGNORED>

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

Wagons, good call on fusing the tails. I hadn't thought of placing a lower amperage fuse after the switch. I'll be looking at dropping the lows out on high beam. I'll put a meter on the switch to see what my options are. I've got 9 relay positions to play with and they're spoken for.

As for disagreements, that's half the reason to post. You can hash out ideas in great detail that way. You might note that I agreed with something of an expert about 90% and as for the 10%, I am on the fence based on other considerations.

_________________
1960 Seneca 225 turbo soon to be EFI

I did some searching and identified the small rectangular relays in the Caravan fuse/relay center as 1/2 ISO relays. They are used on circuits less than 20 amps.
If I decide that a light duty contact is acceptable for a few loads, that will free up 3 Bosch ISOs.

_________________
1960 Seneca 225 turbo soon to be EFI

Here is a list of circuits I'd like to have powered through relays:
Ignition
Fuel Pump
Headlights
Overdrive enable
Overdrive speed sensor
Heater blower
Wiper
EFI (future)
Horn
Cooling fan

The Normally open contacts on an ISO relay are rated at 50 amps. So one space saver might be to run a #8 wire from a relay energized through "ACC" to a 6 position common buss fuse block under the glove box. The one I found has spade terminals for loads and grounds and 10-24 studs for power in and ground. (nice).This could conveniently feed heater blower, wiper and radio, freeing up one space.

_________________
1960 Seneca 225 turbo soon to be EFI

Be sure to take those Amps ratings "with a grain of salt". You don't want to load any component more than 75% of its rated capacity- personally I'd go a little more conservative & aim for 50% max. The weak link I tend to see in electrical systems (ie. cause of failure) is often the connections. The "solderless" crimp connectors that have the red/blue/yellow sleeves are junk.

_________________
63 Valiant Wagon
225 - 4 bbl

I was figuring 75% max and err on the conservative side wherever possible.

Thanks again, mcnoople for the CAD tip. I bought icircuit for iPad. It's a circuit simulator for pcb design primarily, so it doesnt have all the symbols I would like. The symbols can be named and values shown or hidden, so I was able to adapt them for a hybrid ladder/schematic to document the terminals in the fuse/relay panel. Three or four of these should cover the whole thing. I could add text boxes to indicate relay pin numbers, but I don't think I can number the wires with them. the program won't let me duplicate any designations.

This is about as large a diagram as I can make on one page. I expect to be able to make sub-circuit drawings for most of the car.

_________________
1960 Seneca 225 turbo soon to be EFI

After trying to arrange the relays to allow for proper headlight operation, I started checking into exactly what "future EFI" entails. Several relays and lots of soldering.

I've decided to use both the Ford 4 relay and Chrysler 12 relay panels. The Ford will house relays for TFI, EEC and sensors, HEGO and MAF.

Chrysler gets:
Fuel pump 1
Fuel pump 2
Cooling fan
Headlight high beam
Headlight low beam
Accessory
Tranny overdrive enable
Tranny overdrive shift
Horn

_________________
1960 Seneca 225 turbo soon to be EFI