It's a microswitch. Three connections, one common, one normally open, one normally closed. Fairly standardized items, pretty sure there's two that size as safety switches for the door in my microwave oven, but versions without the extra arm. If you're using a computer the mouse buttons will be using a smaller version for through hole soldering on circuitboards.
Thank you G-son, I listed my wire gauge since I'll never understand how to use it, I can spend the money it will generate.
I only have one fuse on the headlight switch on my ‘56 F100. Factory installed. Do I need to add another fuse for protection? Where would it go? Thanks from a wiring newbie…@CrazySteve
Can you show how to do this with two relays; I came up with the having to use 3 relays to run my windows with a toggle switch. Two to reverse the wiring and the third to control the power.
Here ya go.... I'm showing the control and motor power circuits separate for clarity. These are standard Bosch-type SPDT relays set up to operate one motor. 87 is the normally open contact, 87A is the normally closed one and 30 is the common. 85/86 is the relay coil power.
@Crazy Steve, I'd appreciate your feedback on a question and two rough schematics I drew up. First, after doing all the calculations you recommend, my car requires 65 amps from the alternator at 125% total continuous load. Mopar one-wire alternators come in either 60A or 100A. 60A would put the output at 115% total continuous load. Do you think I'm close enough to go with a 60A, or should I plan for a 100A? It's a street-strip car that I highly, highly doubt will ever require running the wipers, both heater motors (it has two separate motors), and high beams all at the same time. As for the schematics, the first is the fuse feed based off a 100A alternator. For a 60A, I'd just as soon use the same gauge wires and setup unless a smaller breaker is necessary. My questions are (1) do you see any issues with the design and (2) would you use a circuit breaker or delete it and ensure the #4 welding cable coming from the battery is well secured and protected? I don't particularly like the idea of having an unprotected section, even if only a few feet long, but I prefer to not use a #6 section as a fuseable link. The cable from the battery to the starter is about the same length and unprotected, which makes me question if I should bother with the main breaker. The second schematic is the headlight circuit. My headlight switch doesn't have an integral circuit breaker, and I can't use a late-60's GM style switch as much as I'd prefer to. Many diagrams I find online and in books show the high and low branches each having a relay powered off the battery through an in-line breaker with the trigger running through the dimmer switch to the headlight switch. Wouldn't using a single relay downstream the circuit breaker as I've detailed protect the switch and wires, bypass sending current through the headlight switch and instead rely on the dimmer switch for full current? If it matters, the car has two headlights rated at 4.5A high each. Thanks for your input.
OK, for the alternator I'd go with the 60A unit. At 115%, you have enough 'headroom' under your worse-case scenario to not have any issues. Just be aware that if you decide to add anything electrical later you might not have the capacity. The panel feed I like. Your using large enough wire to fully address voltage drop to the panels which is 90% of the effort to have a properly-sized harness. This is where the 'kits' as supplied fail. I wouldn't bother with the fuse/breaker as your branch circuits are all fused, so the only thing you're protecting from is catastrophic accident damage, if that's the case this is probably the least of your problems. So as long as the wire is routed carefully and adequately protected no fuse protection is needed. I would keep those #10 feeds to the panels as short as possible however by mounting the relay as close to the panels as you can. Wire length should be inches and not many of them. This is the weakest point in your schematic, excess length there will affect everything downstream. The lighting circuit I'd like more info. Not having an internal circuit breaker in the switch isn't a deal breaker but it does complicate fusing. Modern switches have two power inputs, one for headlights and one for the rest. If the switch you're using only has a single input, best practice is to fuse the tail/dash lights separately but that means some sort of in-line fuse arrangement. Is this a new switch, or a 'vintage' one that may be a bit suspect as to condition that you don't want to trust? If I knew how the switch is configured, I could be more specific. And keep in mind that 'headlight relays' are almost always a 'solution' to the problem of excessive voltage drop at the panels. If the panels don't have that drop and you have quality switches (light, dimmer) capable of the loads, the only time you need a relay is if you have a 4-headlight car and decide to step up to legal aftermarket 60W high beams. These will be more than the typical 15A internal breaker can carry (5A each) so running two of them through a relay will fix that. With only 2 headlights (of legal wattage) I don't see a need for a relay. I would drop the circuit breaker size down to 20A.
Thanks for the input, @Crazy Steve. I'm following all your points in your response. After spending the day going over the build with my friend--the car owner--and going through the different components for load, measuring, and doing all the math thrice, we landed on much more amps than originally planned, so I'll plan for a 100A alternator. I'd like to address a few of your comments/questions and then provide what I worked on today for your input before purchasing parts. My current layout is to put the relay at the top left kick panel under the dash with the two fuse blocks below it in the kick panel. I know up under the dash will be a cooler place, but there isn't room. The #10 feeds would be under 12" in this configuration, and I might be able to get the longest down to 8". The fuse blocks I'd like to use have a #10 max crimp connector (links to the blocks below). Using the NEC calculator, #10 at 13.5V, 0.5' long, at 54.8 amps (the sum of the large continuous fuse block with the 12.8A intermittent factor), voltage drop is 0.41%. What is a good maximum drop for these feeds before they create issues down the line? The 1/4" threaded lug fuse blocks I've found where I can use #8 or even #4 feeds will present wire routing issues compared to the following blocks. #8 would bring the drop to 0.25%. #4 would be 0.10%. Likely fuse block due to compact: https://www.delcity.net/store/ATO:ATC®-Block-!-8!Way/p_10823.h_26531 Larger block but possibility: https://www.delcity.net/store/ATO:ATC®-Block-!-16!Way/p_821858.h_821859 Inline block if ever necessary for components: https://www.delcity.net/store/Standard-Fuse-Block/p_795858.h_795859 The car is a 1956 Dodge Lancer. I'm dismantling all the original switches to clean, inspect, and grease them and intend on using as many as I can, replacing with NOS if needed, or converting to a modern universal for the more basic on/off rotary switches (e.g. heater blower). The headlight switch, however, is a very odd beast in its actuation because it converts the vertical lever action (full up = off, one click down = parking, full down = running) into rotary action at the switch that is mounted sideways, so I can't use a later GM style switch as much as I'd like to. I pulled the switch today and took the multimeter to it to see exactly how the juice flows, found an image of the same switch, and made some notes for you about how the OEM functions and my proposed wiring modification to run the headlights off a relay. Does my plan pass the test? If you think a headlight relay is not the way to go, the other way I see separating the headlight from the other circuit would be to run the switch feed through the 20A circuit breaker in the fuse panel and then run the pigtailed tail/instrument branch out of the switch through an inline fuse and the pigtailed front parking lights/ignition lock light branch out of the switch through another inline fuse. As for the other work I did on the design, here is the build sheet per your recommendations throughout this thread. I'm fairly confident I have all the math correct but have two specific questions: 1) I added the 80% intermittent factor (12.8A from the lighter) to both the unswitched continuous and the switched continuous sums for a total of 25.6A intermittent factor. While a larger number, I can see how it applies if, say, the driver has to mash on the brakes and horn while something is charging in the lighter. Is this doubling of the intermittent factor appropriate, or have I added too many amps? 2) Am I good on the emergency flasher situation? As you pointed out, the sum that dictates the necessary fuse is large, but the actual physics divides this load across four wires. As I have the build now, the turn signal wires work at #14, which will result in only .94% voltage drop for the longest 20' single flasher light with the wire protected by the 20A before reaching the 25A at 90C rating. Thanks again for the review and input.
You've pretty much got it, just a few things I'd change. I'd bump that #4 to the 100A relay up to #2. That wire will be your main source of voltage drop to the panels. I'd use the same size for the alternator output to the battery, for the same reason. Recalculate with the bigger wire, and if total drop from each piece added together is 2% or less at the panel, it's good. I'd also only add the largest intermittent in once. Again, these are short-duration events and if your drop numbers are good (and yours are!) you'll see little effect. A few nit-picks... I'd bump the turn signal fuse up to a 15A to prevent nuisance tripping in the event of a failed lamp, although there is another issue. You show four brake lights, but a 7A fuse won't be big enough if switching three turn lights (two rear, one front). I'll note that Chrysler typically on this-era multi-taillight cars wired only two for brake/turn/taillight, with two being tail-only. You can wire them either way, but it does put additional load on the brake and turn switches if you do four in the rear. FWIW, I've done this with no ill effects but YMMV. If you decide to run two as brake/tail only, you'll need to run another wire from the brake light switch to the rear of the car. And I'd use a #12 to feed the emergency flasher switch, the #14 from the switch to the lamps is fine. Last, the light switch. Yeah, Chrysler used some weird switches in the '50s, unlike anybody else's. The first thing is that 'relay' isn't a relay, that's the circuit breaker for the lighting. I don't know just how they protected the various circuits; I'd remove the breaker then check to see which terminals go dead when operated. If it's protecting all of them, I'd probably just wire it up as per OEM after re-installing the breaker. You may want to install a new breaker (of the same size) for reliability just in case. I still wouldn't use a separate relay for the headlights unless there's concern about the switch contact condition, which could be checked by rigging up a loaded circuit then checking for drop across the switch. A few tenths of a volt drop would be OK. A #12/20A feed circuit to the switch should be more than adequate. As shown, you've got your total drops at the branch circuits (including the drop to the fuse panels) down to under 5% which is right on target for no issues with dim lights or badly over-sized fuses for the wire size. Great job!
Wonderful. Thanks for the help. I have a couple last things to review: The car originally had two brake and two reverse lights. For better visibility at night and since the reverse lights aren't really needed for the owner with bright tail/stop lights activated, we decided to convert the reverse lights to tail, so the car will have two brake and four tail similar to other models like you describe. It will have two turns each side (one front, one back). Sorry if my spreadsheet didn't make that clear. I like the idea or setting up all four rear lights as brakes, but I'd have to go with #12 and worry about the impact on the brake light switch. You having done it before makes me curious to attempt it, and it would be easy enough to abandon two of the brake lights in the future if there is an issue. It would certainly help tell distracted drivers the car is stopping. For wiring, I'm using a universal GM turn signal switch and plug. The "relay" is a typo on my part; I meant circuit breaker. My other modified image shows how the branches use the breaker from what I found examining the ohms. To summarize what I found, the breaker protects the headlights, taillights, instruments, and dome/map lights when switched to the run position. The front parking lights are never protected by the breaker. My issue is if I run the switch per OEM, none of the branches will be fuse protected and will be on the same circuit as the headlights, aside from the dome/map lights on the "A" lug that I plan to bypass and run through the fuse panel instead of picking up power at the switch. If there isn't anything problematic about not fusing these branches and relying on the breaker, I can wire it up OEM and run it. My thinking of using the headlight relay is so I can separate the headlights onto a dedicated circuit protected by the 20A breaker in the fuse panel and put the taillights, OEM instruments, and front parking lights on a separate fused circuit. Here's a sketch to clarify the idea. Maybe I'm over-engineering the switch wiring, but since I'm starting from scratch I'd prefer to get as close to an optimal design as possible. Let me know what you think. Thanks again.
I noticed a few other small things. Now as to the 2 vs 4 tail/brakes, that's your call. But one I'd do is size the fuses to the wire; that is what we're trying to protect. So if it's #12, use a 20A. #14, move up to a 15A. Use a 10A for the #16. That eliminates the odd sizes, reducing the number of sizes you need to keep at hand without sacrificing safety. Yes, some fuses are bigger than they 'need' to be, but the wire is rated for that current, the fuse will protect it. Fuses don't protect the device, they merely disconnect it when it fails. The larger fuses will sharply reduce any chance of nuisance tripping and may keep marginal bits working a bit longer if they do start to fail. That leaves the lighting and that strange switch. It's obvious that Chrysler has a bit different philosophy as to what is 'critical safety' lighting with all going through the breaker. Ford and GM used circuit breakers for the headlights only, figuring these are the 'I want on if at all possible' lights with the tail, park, dash and dome circuits being secondary and protected by their own fuses. Unfortunately, the switch has to be configured to do this and yours isn't. So all this leaves you with limited choices.... The simplest one is to hook up as per OEM and call it good. I'm not aware of these switches being problems or Chrysler products having issue with these circuits. I would make an effort to determine the switch condition if I thought it was suspect. Sometimes we overthink stuff... Seriously concerned with the switch? Then your drawing with the relay is a viable choice, although I would change the fuse at the panel to a 15A breaker. That will give you more leeway in terms of how long the lights will be able to operate and won't require a fuse replacement if it does trip. You will still have the problem of losing all lights when it does though. You can't feed these secondary circuits separately without going through the switch unless you add yet more relays, a needless complication IMO. The breaker will protect these circuits however (although I would upgrade the dash light wiring to #14) so this is a 'safe' choice. The 'ultimate' solution if you want the maximum protection with the best chance of retaining more operation of the lighting circuits in the event of an issue would be the above choice with some added bits. Install in-line fuses in each secondary circuit; tail, dash and park. Use a 10A fuse in each, this will ensure the fuse will go before the 15A circuit breaker feeding the switch will trip. But this is getting complicated.... I'd also check the switch to see if it has an on/off function for the dome lights; some do. If so, I'd leave the feed at the switch for the convenience. If you feel the need for a fuse, use another 10A in line. All this help?
Okay, I'm not really into electric stuff - so bear with me. Today I found out, why my electric fuel pump stopped working, the ground cable slipped out of the connection, so I put on a new eyelet and reconnected it (basically to a screw in the sheet metal). While doing this (mind you, the ignition and everything was off) I saw some sparks. As far as I know, one shouldn't see sparks coming out of a ground cable - right? So I disconnected the ground cable from the battery, and measured between the negative pole of the battery (plus still connected) and the loose ground cable. Low and behold - I saw 12V on my multi meter. Did an amp test, and it showed pretty much nothing. Maybe I'm just dumb, but IMHO - with everything turned off - I shouldn't see any voltage there, or am I missing something? Thanks Frank
Not at all, LOL. Yes, this thread and your specific conversation with me is immensely helpful; thanks for taking the time to share your expertise. Now that we've talked through it, I see that the headlights will still be on the same circuit as the entire switch regardless of the relay design I posted, so you're correct I wouldn't want a fuse but a circuit breaker for the tail/park/license branch. I'll think on which way I want to go with that switch, and everything else looks good. I'll simplify the fuse situation and move ahead with the project.
Obviously something is on. Something is drawing current. It may not be a lot of current, but there is some kind of parasitic draw.
Hi there, hoping someone can guide me in the right direction. Do I have a faulty alternator or am I wiring something wrong? I have a Powermaster Alternator in my flathead. alternator is brand new https://www.speedwaymotors.com/Powe...EN-1939-48-Ford-Alternator-12-Volt,98486.html It is wired it with a single wire running from the battery side of the solenoid to the alternator. My problem is, when I crank the engine over, I feel the battery literrally getting hot. The engine drags, as if the battery is low, and the engine won't start. I think the alternator housing/mount is positive too.. If I remove the wire going to the alternator from the solenoid, the engine turns freely and engine starts right up. I disconnected the wire from the solenoid, used a continuity tester on the wire and it shows to be working well. however, when I touched the alternator housing with the tester, the tester lit up also. Shouldn't there be no continuity to the housing and the stud on the back of the alternator be isolated? Thank you for any help. Totally newbie on electrical so I apologize for my basic descriptions and troubleshooting.
It sounds like your alternator is not well grounded to the engine, and/or the engine is not grounded well to the chassis. Do you have a ground strap between the engine and the frame? The starter motor may also be dragging.
This is a really outstanding thread by @Crazy Steve and should be immediately immortalized in the Tech archives (if it hasn't been so already). Wiring is one of those things that every car, no matter what style of build, requires. It shouldn't be taken for granted. Big thanks and major respect for this thread. More of what the HAMB needs.
The fact that disconnecting the alternator seems to clear the issue makes it the number one suspect IMO. I'd pull it and have it tested before going further. I wonder if you got a 6V positive ground unit by mistake.
Engine builder supplied the alternator but didn't provide an actual invoice for it for me to verify. Removing and having it tested sound like a good idea. Thank you for the advice.
As "57Joe" stated, such a great thread by Crazy Steve. A favorite read of mine. It is just loaded with helpful info. Thanks
You were right Steve! Some how the engine builder installed a 6v positive ground unit. When I sent it to Powermaster to have them check and fix it, they called me back and told me that nothing was wrong with the unit but everything was wrong for it since I needed a 12 v negative ground unit. They were great to work with and just charged me for the difference to the right unit and sent me a new 12v negative ground unit. Thank you for the help!
This might be a dumb question, but what type of connector should I use for a “higher” amp circuit? Say in the 30 amp range? I am using one of these yellow butt connectors in my electric fan circuit, and it has now melted twice, right at the butt connector. I’m using 12 gauge wire on this circuit.
First, you need #10 wire, not 12. 12 is only rated for 20 amps. And how are you crimping this? Read this... Technical - Crimping Tutorial | The H.A.M.B. (jalopyjournal.com) If you're crimping with the plastic sleeve in place, you're probably not getting a full crimp.
Agreed, most auto store crimpers don't have the correct shape, not enough bite or leverage to crimp down on those connectors. Might have to use the uninsulated tongue & groove crimp tool to attain a proper crimp. It wouldn't hurt to put a little antioxidant(Ox-Gard) on the wires before crimping for added protection.
I found a great ratcheting crimper at Advance Auto Parts. It was like $40 and is very adjustable. I have barrel-type crimp sleeves in my car, all samples from Tyco/TE from work. Anything exposed to the elements I use a shrink sleeve with adhesive inside of it so it seals well. I used to get out-of-date shrink sleeve at work. I think we went with 6-months or a year and then stock was purged. There was a set of shelves outside the stock room and we were told to help ourselves.
The Jalopy Journal
