Hey guys, I hope my question isn't stupid! I made the entire harness for my little '27 Roadster, and everything seems to be working fine except the charging circuit. The car is running a little 302, and it used an external voltage regulator. I wired the regulator terminals correctly, but didn't use the "I" terminal, since I always assumed that is only for a charge indicator light on the dashboard. I just have the other three terminals properly hooked up (A to BAT, S to Stator, F to Field). Do I need to have the resistance of an indicator light connected to the terminal "I" on my regulator in order for proper charging, assuming all other parts and pieces are working and connected right? When I test the new alternator, it only raises the charging to about 12.6 volts, and that requires at least 1200 RPM's. Any help appreciated.
The "I" has to be hooked up to excite the field. Did you try to full field the Alt to see if it is working?
To give you a little more info about that circut, Ford used a 15 ohm resistor in parallel with the indicator light. It was there in case the bulb burned out. You need to use ignition switch voltage for this as the battery would run down if you left voltage at "I" when the engine is not running. Hope I didn't muddy up the explination to bad.
Coupster is exactly right. Run 12v from the ignition or running accessory supply through a 15 ohm resistor to that terminal whether or not you use a charge indicator light. Use a 1 watt resistor or greater. This works the same when you use a Ford 3G internally regulated alt. I found that out when adding a 3G to my '58 Ford.
I've always hooked them up the same as you did (CRH) except-the S terminal on the regulator goes to a key controlled ignition source (no stator wire is needed at the alternator). http://www.oldcarmanualproject.com/tOCMP/wiring/5765wiring diagrams/Ford/MWire5765-237.jpg http://www.oldcarmanualproject.com/tOCMP/wiring/5765wiring diagrams/Ford/MWire5765-236.jpg
Holy Moly, thanks for this helpful, straightforward info, people! I'm very grateful, and the reason-why type explanations I like best are what you people have provided. Thanks!! I'll wire the '27 correct tomorrow...
Hey guys, one more question: Is it bad to simply have the "I" terminal run straight from a switchable power source, like the ACC part of my ignition switch? I tried this for fun and it did as stated previously; it excited the field. I'm just wondering if and why a resistance must be part of that circuit...? Is it too much amperage, hence the use of 15 ohm resistor by Ford?
Well, first, I must correct my previous post. I took a look at my factory data and the resistor is 560 ohms, not 15. Sorry for the bad cheese. The resistor is there to simulate the DC resistance of the charge indicator lamp should that lamp burn out. I have heard of people wiring it up straight without either lamp or resistor but I think I would use a resistor anyways. Another poster mentioned a diode. You have a 50/50 chance of getting that one right. Just get a 470 to 560 ohm 1 watt resistor or a pair of 1K 1/2 watt resistors and put them in parallel, solder on the wires, use two pieces of shrink wrap (shrink one at a time) and there you have your inline resistomathingie for much charging goodness.
That makes sense, no worries. I'm just too "in-the-dark" about why there should be the resistance. I'm scared that maybe it lessens the load on the "I" terminal for a good reason, like protection or something...? I have driven the '27 for the past two days with just a straight wire from the ignition ACC side to the "I" on my voltage regulator, and the alternator charges great. But, does this mean it is overcharging or that my un-resisted wire will eventually burn out the voltage regulator?
This is how I wire a Ford alternator w/ external regulator, except I delete the amp guage (fire hazard), and use a volt guage. Been wiring then this way for over 30 years with no problems.
It's an old post, but I've been trying to get the charging system fired up on my 48 F1 302 redux for....well, more weeks than I'm comfortable admitting. Thanks for this quote, Coupster...things are working as they should now. I ended up using two 7.5 ohm Brown Devils in series (all I had around here), and EUREKA! Thanks
This is almost exactly the way Ford wires them when using an ammeter and no idiot light.... The only difference is Ford runs the wire from the 'A' terminal on the regulator to the starter relay, but this will work.
I'm trying to adapt the wiring schematic from a 1977 F-series truck to establish the basic wiring necessary to run in my 351W and AOD. I've got a wiring chart from the '77 F-series truck and the schematic for the 76-77 Duraspark II and all the pieces for the system: Starter, alternator, regulator, distributor, coil, ignition switch, starter solenoid, resistor wire, ignition module (blue insulator), connector plugs and even the voltmeter. Some of this I've figured out from both the F-series schematic and the 76-77 Duraspark II schematic. But I'm not sure where Regulator wires yellow (AT) and green (I) go, and where the resistor wire connects. You've got me baffled regarding the "I" wire, resistors, idiot light, etc. Huh?
Note that the last post above yours was 8 years ago. The problem that you are having is the same problem that every mechanic that wasn't a Ford mechanic in a dealership had when those were a lot newer. There are too many frigging eithers, ors or iff's. Moms 77 has a 300 in it but someone in the past took the electronic distributor out and tossed it in the trash and put a point style distributor in it for that same reason. There are too many variables. There are about three modules that fit the same truck and same engine depending on the mood the day the truck was built. There are some other differences too but I can't remember them. If it is in a hot rod I'd toss that setup and put a point style distributor or an Hei in it and never look back.
Yeah, I know I'm resurrecting an old thread, but it was the closest I could search to address the issues I am having. I hope that asking specific questions might lead to specific answers, or at least help me better understand the electrical system of the engine I've rebuilt. Hotrodding is mixing and matching, but so far I'm struggling with the matching part. Anyone else out there know how to tackle this?