A big Thank you to H.A.M.B. and its members for the help in solving this problem. I spent a fair amount of time searching the board to figure this out and had a lot of information to sift through. Im hoping this post can help others (especially with a part number). I recently finished building a T-bucket and had the problem of the alternator feeding back to the ignition. I used a painless 8 circuit harness but used a tractor ignition switch along with a push button starter switch. The painless diagrams dont account for this setup and as I understand it, the way I wired it, the alternator excitor wire is feeding back juice to the coil wire through the ign. terminal on the switch. I read about using a diode on the excitor wire and felt this was probably the best way to go. After going to Radio Shack without a specific P/N or specs I called Painless and they gave me the Radio Shack part number 276-1661 this is a 6A 50V rectifier diode ($2.49/pk of 4). I wired it up as shown and it works perfect, its charging and I can shut er off. Thanks again H.A.M.B.
Thanks for the feedback! Especially since the GM 10-SI alternator is required equipment in every traditional rod....at least it looks that way..... (yes I have one on my 55)
Delco used to have a resistor diode kit available to fix this problem, but I don't think that it has been available for quite a few years. Your fix looks like a good one, you might think about putting a piece of shrink tube over the diode and connector.
I had a GM alt., single wire, built for my Ford. Went to parts store and bought a spare int. reg to install in a new one,if needed, on the road.
It also works properly if you run the exciter wire to the accessory side of the ignition switch (if you have an accessory terminal). This way it doesn't feed back to the ignition when you turn the ignition off, it's that easy. http://www.americanautowire.com/PDFLink/92968419 510004 IN 1.0.pdf
Installing a #194 or similar dash light in series with the #1 excitor wire will also prevent feedback, and is what GM used for many years. They usually ran a diode parallel with the bulb in case of burnout. The link below has a wealth of electrical info, including the very popular 10/12 SI alternators. http://www.madelectrical.com/index.shtml
Very good info. I had a lot of people think I was nuts with the light bulb on my car...but it worked!
Use one wire Delco instead, self exciting and doesn't need a diode, but the receptecle is still available from an Auto Electric supply house (they also rebuild starters, alt's and gen's) and a good one can modify exsisting parts for special application, sometimes there parts are cheaper than most Auto parts suppliers. been using them on my Fords since they came out, never had a problem
How simple. Worked like a charm. Cut the exciter wire at the fuse box and hooked it to the accessory side of the ignition switch. No more feedback. I fussed over this problem for days before reading the solution. Thanks HAMB
Hey thanks for bringing this old thread up and reminding me! Heading to RS tomorrow for a pack for my 1951 pontiac and 460 international tractor.
The Hamb really is a one stop shop for all the best advice. I had the exact same problem and was trawling all over the internet. Stopped by the Hamb and had my solution in the first post I checked. Ten points.
Had the same problem in an OT car with newer Delco alternator. Turned out the the charging light wasn't working due to a bad connection (oxide) at the bulb. Fixed that and I could shut off the engine with the key again... instead of pulling the ignition wire from the coil. I ended up putting a diode in the system anyway, just in case the connection would go bad again.
Wiring up the exciter to the accessories tab on the ignition switch works a charm. Question though; since there will be some kind of feed back from the coil when the accessories are on, would it be a good precautionary measure to install a diode over the exciter line anyway? Just to save a little more juice?
The exciter wire, (white one) works like this, when the key is switched on, it tells the alternator the ign switch is live and ready. Current flows to the alternator, tells the regulator it's ready to accept a charge, start engine, power flows the opposite direction back to the switch. The ign switch inside is separated from the run side, meaning acc is it's own circuit, when switched off, the acc side is dead and doesn't allow current to flow through the switch. If you hook the exciter wire to the run side, the engine will run on after shutting the ign switch off because it'll bypass inside the switch and not shut off. Clear as mud?
...OR, you could do THIS... http://www.ebay.com/itm/CHEVY-DELCO...cf2233e&pid=100005&rk=1&rkt=6&sd=191103912421
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