The Stovebolt Site Forums The Shop Area The Electrical Bay DA Plug wiring - HELP !

I've just completed switching everything over from 6 to 12 volts. All I need to do is connect the yellow DA plug wire to the ignition switch. All instructions I've seen says to connect it to the IGN post of the switch. There are 3 posts on the switch and I cannot find any markings. One post is empty, one has a single wire which I believe may be going to the + side of the coil and the last post has 2-3 wires connected I believe from the light switch, ammeter guage and who knows what else. Which one do I connect the DA wire to ??

Cmayna here-Forgot to mention It is a 50 3100 1/2 T. with a 235 cu in, if it makes a difference

Connect it to the one that is only hot when the switch is on. You can use a voltmeter or a simple light bulb to tell which one is hot all the time and which one is only hot when the switch is on.

If you are lazy... and will admit it... then you can connect the yellow wire of the DA plug to the (+) terminal of the ignition coil. then you are done. Then you will not have to stand on your head under the dash to hook things up. That is where the lazy part comes in. Thanks Randy.

I resolved the problem with suggestive help from my fellow stovebolters. I traced it down to the fact that I had connected the yellow DA wire to the wrong ignition key terminal. Once I changed it, I suddenly lost the constant draw on the battery. I'll know more tonight when I get home and attempt to start the beast.

thanks to all with your guidance.

Craig

I have a few stupid questions. My truck was converted to 12 volt by the PO and I don't think my battery is charging.

I have an alternator. One wire goes from one stud to the other on the alternator. The other wire goes from this first stud to a ceramic little block mounted on the fender. From this block it goes through the dash to the ignition switch. Then I have three wires coming back from the switch. Two go to the two connections on the starter motor and the third goes to the + on the coil.

Now, this doesn't really sound like the descriptions I have been reading. First of all, what is the DA thingy you all are talking about? Is it correct to only have one wire go to the alternator?

Tony, the only stupid question is the one you don't ask.

The "ceramic little block" is the ballast resistor. It drops the voltage down to six volts (approximately) across the points, to increase point life. During starting, it is bypassed, which gives a hotter spark.

Your wiring is just a bit different from most, but it obviously works fine. The key is to get the alternator wired to something that is hot when the key is in the ON position, but not hot when the key is in the OFF position.

The DA plug is a little device that allows you to use an alternator on these older systems and get rid of the regulator. It provides 12v to the "exciter", to "get the alternator started". Alternators have to have some voltage in order to get magnitized so they can generate electricity.

I know the purpose of a DA plug, however in the last 10 years I have installed maybe 5 GM 10s alternators on generator equipped engines . I just hooked one wire to the ignition and one to the battery. If the engine ran after the ignition was cut, I simply reversed the wires, yup just reversed em .On a tractor conversion, I used an indicator light in series on the wire fed from the ignition switch as in a stock set up . All of the alternators have the resistor across two terminals of the internal regulator originally.3 of these conversions belong to me. Never a problem in the last 5 years ,even after sitting a few months in winter storage. Please explain why this works for me and no one else.

Well, it works, but could it be that my battery is not charging? I have not checked it yet with a voltage meter (can't find it right now) But my gauge doesn't seem to read that it is charging. When I turn the lights on with the engine running it does go to discharge.

It seems the engine is getting juice from the alternator but I am not sure the battery is. At first I thought I had a weak battery and replaced it. But, now it seems to run down with each succesive start of the engine. Though it seems to run indefenitely. Also, I don't see a DA switch, what does it look like?

Warning Do not ever do this with a late model car with electronic ignition, especially is it has a computer.

Remove the negative cable from the batter with the engine running. If it still runs, the alternator is at least working. To confirm that it is working correctly you must use a voltmeter. A properly functioning alternator should generate about 14.5 volts. If it's a little lower, it may indicate a discharged battery. If it's under 12.5, it's not charging and needs to be replaced. If it's over 15, the regulator is shot and you need to replace it.

It's not a DA "switch", it's a DA plug. It's a plastic plug that goes on to the two small terminals on the edge of the alternator. It has a diode in it, but you can't see that. One wire goes to the BATT terminal on the alternator, and the other wire goes to the + side of the coil or ballast resistor or to the ON terminal on the ignition switch.

The battery and alternator are in the same circuit. So, if the alternator is putting out enough current, the battery will be charged up. What can happen sometimes is that the alternator isn't capable of providing enough current for the entire system (big boom boxes will cause this), so the battery has to supplement the alternator's output. This will cause the battery to discharge.

Ok, I will spend some time looking for my voltmeter today. Thanks for clearing that up. I just figured since the wiring looked different from the different tech articles I was checking, maybe the PO wired it up wrong and no juice was getting to the battery.

One other thought now, ha hmm....

Since the only wire coming out of my alternator goes through this little ceramic block that you guys say reduces the voltage to 6 volts, does this mean my battery is trying to charge at 6 volts??????

If you look at the wires that go to the ballast resistor, one is "hot" and the other goes to the coil. Either one will work fine for the alternator.

Check out my earlier post explaining how my system is wired.

I have one wire on the alternator that connects two connections on the alternator. From one of those connections, a single wire goes to the reducer block. From this block I have a single wire going to my ignition switch. From the switch I have 3 wires coming back out through the firewall. Two of those wires go to the starter, the third wire goes to the + on the coil. (I have keystart)

Now, since I only have one wire coming from the alternator and it goes through the little reducer block, does this mean this effectively makes my whole system 6 volts? Including the part that charges my 12v. battery?

No. Your alternator should have three wires; one on a post near the center of the back, and two going to terminals on the edge of the back. The one in the center should go directly to the battery, and that is what charges the battery. The two on the top should go to the ignition switch, coil or ballast resistor (B) and to the center post on the alternator (A).

Without a diagram, I can't be sure, but it sounds like your wiring is bypassing the ballast resistor completely. Are you still using point? If so, have you been going through a lot of them? Could you possibly post a picture of your alternator?

Just bought the truck so don't know about the points. But, the wire that goes from my altnernator to my ignition switch goes through the resistor. So doesn't seem to be bypassing it.

I did not find another wire that goes to the battery from the alternator. I am going out now to look. Could it run without that wire? It would explain the non charging.

Also the PO said doing it this way he didnt have to change any bulbs or anything.

There is no other wire. The alternator has two connections. One has a red marking +?, the other is smaller. The two are connected together with a wire. Then another wire goes to the reducer block. From there the single wire goes to the ignition switch. From the switch, two wires go the the starter and the third to the + on the coil.

The trucks runs great, starts easy, turns over readily.

Come on guys, I am dying here....

When I was out checking I was feeling the little jumperwire that goes from the big alternator red post to the littler spade connector on the side and the connector was loose. This might have been my problem right there. After recrimping it I was putting it back on the spade connector and touched the side of the alternator with it and got a spark. So, with the key off this wire has some juice going to it.

Wow, 400 people on the site and nobody knows the answer...

Just to be sure that this is all clear. From your DA plug, you should have two wires. A yellow wire goes to the ignition side of the switch, where the other wires are connected. The red wire goes to the power post on the back of the alternator. Also attached to the power post should be a 10 gauge wire that goes straight to the positive of a 12 volt battery. No resistors in this circuit. You should have a ballast resistor going to the coil, and resistors going to any appliances that were not changed to 12 volts, gas gauge is the biggie. I recommend getting a 12 volt internal resistor coil, then you can eliminate the ballast resistor, but your truck will run with the resistor that was for 6 volts, but you will eventually burn out your points due to high voltage.

So, am I assuming correctly my setup is wired incorrectly?
First of all, my alternator only has two connections and only one wire that goes to the key.

Secondly I don't see a DA plug.

So, I am missing wires, DA plug and a place to hook them on the alternator.

This still doesn't make sense to me.

Is my current setup charging at 6v?

Thanks for trying to help. I am stumped.

Ok, I just reread your post a few times. I think I can do it from that. So basically my setup is all wrong. Thanks

I am not familiar with a DA plug, although I have made a wiring harness that does the same thing.

Looking at the back of the Delco 10SI alternator, you will see the large threaded post that the heavy (10 ga or thicker) attaches to. The two smaller wires go into the side of the case right at the back of the alternator. The terminal CLOSEST to the Batt. terminal is the switched terminal, labeled #1 or I. The other terminal located farther away from the Batt. terminal is the signal wire, labeled #2 or S. The internal regulator needs a voltage signal at this terminal so it knows how much current is needed to maintain required voltage. That is why you just need a small jumper wire from the batt. terminal to the #2 terminal. It can be hot all the time and will not cause any problems.

The #1 terminal is fed from the ignition switch. Any voltage from 2 to 11 volts is acceptable. I use a light bulb in series for feeding the #1 terminal to drop the voltage, but also as an idiot light--if the light is on, the alternator is not charging.

I do not know WHY the #1 terminal should have reduced voltage applied to it. I have studied the wiring diagrams and can't seem to figure it out. My only theory is that when you shut off the engine, the voltage present in the #1 terminal cannot backfeed with enough voltage to keep the coil engergized and the engine running.

Do two wire alternators exist? I see the bigger stud you mention, it is colored red. Then low on the alternator is a tiny spade connector. It has a small jumperwire that connects to the big colored red stud. That is it, no other connections.
Then I only have a wire to the key, none to the battery.

The H*** with the DA plug thing! :rolleyes: Buy the "self-exciting" regulator or "one-wire" regulator from your rebuild shop, install in alt and Hook up the big stud to your plus battery cable on the starter with 10 gauge wire (red is common color) and you're done. Won't charge at start till you "blip" the throttle up a little, then begins to charge and stays charging even at idle. One-wire, just like they call them. You need to have the big 10gauge wire to battery or term on starter where batt cable connects for your set-up too. Don't see why you need the Resistor on firewall, cept to power your coil with smaller volts than the 12 it would otherwise get. Shouldn't come off the alt at all. AND YES, you will have to change all the bulbs, headlights, and heater motor to 12 volt stuff or use reducers on the heater motor and the gas gauge too. Gas gauge will burn out shortly w/out reducer.

All the parts are brandnew. The PO had just done the change to 12v. I think he thought that if you run the alternator's entire output through the ballast resistor that the truck would basically still run at 6v. but, I think the problem with that is that the battery is trying to charge at 6v. So, really pretty hard to figure out something is wrong because it takes weeks of use to run the battery down enough to notice a difference. And ofcourse the first thing I did was buy a new battery which delayed things even more.

So far I have been told my alternator is supposed to have 3 connections and not two. I have been told I should have a DA plug which I don't. And there should be a wire that goes from the alternator to the battery.

Apparently I do have some kind of direct line to the battery through the switch because the wire to the alternator has juice on it without the key being on. BUT, and this is the big BUT, this line runs through the ballast resistor and I guess is also reduced to 6v.

So, maybe the wiring isn't that bad. Maybe he just put the ballast resistor in the wrong place? He put it in between the alternator and the key, thinking this way he wouldn't have to change any bulbs and stuff.

What if I take the ballast resistor out of the line between the alternator and the key and install it in between the key and the coil (or is it the distributor?). If I do this after changing all the bulb etc, because my dash wires would now have 12v, the whole truck would be on 12 v except for the points?

Re-read my post.....ONE-WIRE! That's the way to go. Ask any gen rebuild shop about it. Can change your existing alt to one-wire, cheaply. Then, 10 gauge wire to batt or starter term from batt. Done!

I am trying to stay with you here. So, you say get a regulator installed in my brand new alternator? The alternator only has one wire now, could it already be set up that way and just wired wrong?

Something tells me the confusion is due to the different alternators used over the years by the factory and aftermarket on GM engines. Every style connected to the wiring differently.

1) The alternator that uses a "DA" plug. Its a 3 wire alternator. "BATT" terminal went to ammeter or directly to Battery Positive. The large wire on the "DA" plug is tied to the "BATT" lug. The smaller wire on the "DA" plug goes to a switched hot on the ign switch. (Factory)

2) Some GM alternators used an external regulator, ala late '60s Pontiacs. These usually have two or three threaded lugs on the back of the unit. One would say "Field" and one would say "ARM" like an old generator. Some have a "BATT" output also. These systems usually had the "BATT" idiot light on the dash, run by the external regulator. Not seen very often anymore, and they won't work right without the external regulator. (Factory)

3) One wire alternator. Basically similar to the "DA" plug model, except the DA plug is not connected. "BATT" lug is connected to battery positive. I believe that this version cannot be used with an ammeter in series with the "BATT" terminal. Must use a voltmeter to monitor system performance. Will not charge until RPM goes above idle the first time. (Not sure, think aftermarket)

4) Aftermarket "racing" alternators. Light weight, high output, low HP drag. No voltage regulation, racing/street rod use only. AC output is fed to an external "bridge rectifier" and resultant DC is fed to battery. (Aftermarket/speedshop stuff)

5) I've seen an alternator used on medium sized tractors. It has a "BATT" terminal and a 1/4" faston blade terminal below it. The 1/4" terminal is energized when the key is on to "excite" the alternator. The "BATT" terminal is connected to the battery. If power is left on the 1/4" terminal all the time, it will drain the battery when the tractor is off. (Factory outdoor power equip)

Most GM guys run the "DA" plug alternator cuz they are dirt cheap and you can get 'em at any parts place.

Hope this helps
Chiphead

Ok, from that it sounds like I have alternator #3 or #5. The #5 sounds spot on except that the wire to the spade connector seems hot all the time and is not draining the battery. So maybe I have #3.

Do we all agree that the ballast resistor should not be installed in the only line coming from the alternator? If it is used at all it should be in the wire to the coil?

Here's a shot of the backend of my recently installed Alternator with DA plug attached. I cannot believe how easy my truck starts now since I went from 6 -> 12 volts. Wished I
had done this years ago.


[img]http://www.cmaynard.com/Alternator.jpg[/img]

I inserted my Ballast resistor between the ignition switch wire going to the + terminal of the coil and the + terminal of the coil itself.

TonyM,

I hadnt hooked up my alt. either till yesterday after reading balds message. My alt is an older deltron gm alt. It has the hot wire from the battery side of the ignition switch,the DA plug-in
2 wires to it. One wire being blue came from the on side of the ignition switch and the other which was black,from the factory wiring was black, that confused me , I thought it was a ground,but I attached it where Paul said also to the stud from the battery side of the ignition switch and Dern if it didnt work. I donot have a resistor block, I am using a internal resistor coil,$16 from napa.I think you should exclude the resistor block and try running it this way with a 12 internal resistor coil,it seems like your system is a little rigged and making it complicated without being there to see it.Hope you get it straight,wiring can be frustrating.

Alan

Ok, just spend some more time tracing things.

First of all, my alternator is a Delco single wire. It has the big stud marked BATT and then TWO spade connectors together. One marked 1 and the other 2. There is a jumper wire connecting #2 with the BATT stud.

I am kind of thinking this is the alternator that doesn't need the DA plug? It looks a little different from Craig's.

Now, I had my head under the dash and I need to revise my original description a little. The wire goes into the dash and gets spliced into everything including the switch. From the switch there are 3 wires going back through the fire wall. Two go to the starter and one to the + on the coil. (keystart)

So, eventhough I don't have a direct wire to the BATT, it does go there but through the dash and I assume an always on terminal on the switch. I guess this is why the PO used 10 gauge for everything.

So, basically he hooked everything up so it will work. Only, his big mistake was to put a ballast resistor in the line that comes from the alternator and powers everything. This is why he told me that the way he did it he didn't have to change any bulbs or anything. This is why he has no resistors anywhere including the gas gauge.

This is why the gauge is always pegged full. I am thinking that the ballast resistor is probably letting through a little more than 6v when the engine is running and this makes the gauge read full yet is not enough juice to blow it up, which is what many of you said should happen to a gauge on 12v.

So, this is what I think I have to do.

1. Change all the lightbulbs to 12v.
2. Put a ballast resistor in the gas gauge circuit.
3. Take the existing ballast resistor out of the alternator line and install it in the wire to the coil instead.

Is that it? Would it be better to add another wire straight to the battery or + on the starter instead of making all the juice go though the dash? Or is this an acceptable way of wiring?

Tony,
I believe you need a runtz resistor for the fuel guage. You're correct regarding the ballast resistor goes between the coil wire (from the ign switch) to the coil.

Craig

Ok....So how many of you own combines? How many of all get together and work on those combines at the same time? Ha Ha it is the two old men working on a combine story...... Oh well....Meanwhile.....

A DA plus is simple wiring harness that I designed that solves two different but related problems. First you need someway to insure the alternator will begin charging as soon the the engine is started (in other words you need to excite the fields inside of the alternator) For most modern applications this happens easily because of the magnetism stored in the rotor is designed to be released at engine idle which in this case is about 1200 rpms. Because most of our old trucks do not idle at 1200 rpms (more like 600-800 rpms) the yellow wire of the DA Plug is used to excite the fields much the same as happens in modern applications.

The second thing a DA plug wiring harness does, is allow you to turn your truck off and on with the original ignition key. Because an alternator is able to produce current at idle and low rpms, whereas the generator did not, the output from the alternator will keep the coil hot and your truck running even though you turn the key off, How embarrassing!!

The solution for GM was to introduce the "accessory" type ignition switch. The accessory post of the new design switch was isolated from the rest of the switch terminals, which stopped the flow of current to the ignition coil when the switch was turned to the off position.

I use a specially designed diode as part of my DA plug wirng harness which stop the flow of current to the ignition coil when you turn the original ignition key off. Thus you do not have to replace the original ignition key assembly to make your truck shut off. All of my dealers sell DA Plugs and they all cost the same if you buy them from me or one of my dealers.

By the way a DA Plug is not the same as the $1.50 harness that you can buy at the local auto parts store. Those do not have the diode included so if you buy one of those, you alternator may charge but it will not shut off with the key....

And nope you can't buy the same diode I use at the local radio shack store, Mine are much heavier and built to totally different specifications (mine) to last a lifetime. Radio shack diodes will last about 6 months and leave you stranded. Ask those who have been there and done that!

Finally DO NOT EVER remove the battery cable to see if an alternator is charging, the voltage spike you create will travel to the inside of your alternator and it will for sure not be charging for long. Instead all that you need to do is touch the smooth bearing surface on the back of the alternator with a screwdriver. (By the way this works for all alternators) If the alternator is charging this surface will be magnetizied. if you are unsure turn on the heater blower motor and or headlights to create an electrical load, then you will have no doubt.

Class dismissed, please pass your papers to the front, your grades will be posted on the bulletin board by Friday noon. Randy.