2606 Delco single wire alternator

Hi, the cub wiring question got me thinking about my 2606 alternator that has me stumped. It is a single wire 12v alternator that just barely shows a charge or discharge of maybe 1 amp or so on a 30 amp guage. I can see the needle deflect slightly is all even when I put the lights on brights. It has always done this since I had it but seems to keep the battery up after running even when I jump start it.

I just recently rewired it except for the 10 guage wire from the alternator going to the positive side of the ammeter. I replaced the ammeter thinking it was bad cause I never really saw it budge. The new one just budges enough I can tell it moves.

This is a replacement engine and has a 4 wire voltage regulator. When I took out the old wire bundle, all the wires to the reg had been cut by a previous owner. I left it disconnected.

I've looked at all the diagrams that can be found on this site and I think it is wired OK. It has a key switch and then a push button for the starter.

Does this one need an exciter or maybe the alternator is bad? I can run it with the headlights on and hardly any movement on the guage and it doesn't seem to dim the lights.

I also added a voltmeter and think I have a bad battery cell as it starts with 12v and drops to 10v or 9v with headlights on and then the voltage slowly starts going up like it is charging. A cheap HF float charger keeps it topped off 24/7 for starting.

Kinda stumped here but it gets by. Thanks.

If it's REALLY a 1-wire alternator it doesn't need to be externally excited.

The voltage tells it all. You should be seeing 13.5 to a little over 14 Volts and you're NOT, so the alternator is BAD or there's an "open" between the output stud on the alternator and the (+) post on the battery.

To rule out an open circuit, with the engine running at mid-throttle and the lights "ON", check the voltage at the (+) battery post AND the output stud on the alternator. They should read within a fraction of a Volt of each other and be in the 13.5 to a little over 14 Volt range.

If voltage is LOW at both places the alternator is BAD.

BTW, is the belt snug and the belt and pulleys in good condition (belt not bottoming in any of the pulleys)?

Thanks Bob, I'll check that with a multi-meter to confirm.

Definitely has only 1 big terminal on the back of the alternator and no place for a plug-in either. If the alternator doesn't check out, I can take it to Oreillys for a bench test. If I replace it, should I go back to a single wire altternator or get a 10SI I've been reading about in other posts?

The belt is old but it seems to turn OK. Guess I'll tighten it to see if it makes a difference.

Maybe the battery is OK since the headlights don't seem to dim any with engine running or not running. Float charger keeps it at 12v now till it starts.

As I recall, one wire of the 2 prong connection goes to a switch connection, the other wire connects back into the alternator, then the big wire goes to battery/starter (on my 706).

Is it a Delco 10SI alternator with a rubber plug closing off the terminals on the voltage regulator that would be used for (standard) 3-wire operation?

Bob, I'll check it this afternoon. It has a round red boot (now faded pink) covering what looks like one large terminal. I've never looked under the boot. I don't recall any other places where a terminal or plug could go but I'll get out the fine tooth comb and check.

I will add that the gauge is showing normal Alternator action. They will not show much when the battery is charged. Lights are not counted with the engine running, the only thing shown is battery charge. If charged up it will barely wiggle. with it off, turn on the lights. it should then discharge ~10-15 Amps. Jim

If it's a "Delco" 10SI set up as a one-wire alternator there will/may be a plastic or rubber plug in the area where the white 2-pin plug is plugged into in this photo.

<img src = "http://www.gondtc.com/~blweltin/Bob/AlternatorHarness3.jpg">

A charged battery is 12.9 volts. Alternator is supposed to go over 14 volts. System voltage when the engine is running should never drop below 13 volts.

Try sticking a nail in the back of the alternator - in the Delco "test port." That's what it's there for. If the alternator is good, but regulator not working - it will go to full charge rate when you use the port. If nothing happens, then the alternator itself is bad.

Jim, that is part of what has me stumped. I didn't have lights with the old ammeter but do now with the new one and I barely get a deflection below Zero with engine on or off with the brights on. When its charging, it barely deflects positive. Just enough deflection I can tell it is moving.

The alternator wire goes to the + on the ammeter and the - goes to the starter where the battery connection is. A return wire from the starter goes to the hot on the key switch so it powers up the lights when it is switched on or switched to ACC. I'll post back this evening.

Do you have a "hold against" ammeter? If you do, use it on a convenient place [away from alternator] as far as possible. See what it says as far as output from the alt.
You have the symptoms of a bad diode trio. One, two, or all 3 sections could be burned out. The one wire units depend on speed to initially energize.

From his voltage reading he already KNOWS the alternator is bad!

The battery lead needs to be connected ALONE to one post of the ammeter and the alternator and ALL electrical loads get connected to the other side.

Just got back. It is an alternator similar to Bob's picture but I don't see a number on it. Has a rubber plug where the two spade terminals are. I tightened the belt.

Battery was reading 12-13 volts and 12 volts at the alternator. Not really any change with key on and headlights on except new dash voltmeter showed 10 volts with lights off and 8 volts with lights on even though the multi-meter showed 12 volts.

Went to start it and battery was weak. Put the charger on for a while and it started.

Read 12 volts at the battery but the alternator was reading 42 volts. Headlights didn't make a difference except on the dash voltmeter. Ammeter didn't move much as usual. Checked and found a bad splice in the alternator wire. Cut it and hand twisted the two ends together for a temporary fix. Was only getting sporadic readings at the new splice and battery but nothing close to the 42v that shows at the alternator terminal.

Then I quickly shorted the #1 spade terminal on the alternator to the case with a screwdriver and got a spark. Then the alternator began putting out a steady 15 volts but I was getting a sporadic 12-15 volt reading at the battery. The dash voltmeter got just under 12v then and less with lights on. The ammeter was working now but varied from -10a with lights on to -5a with them off. Not sure what is going on here now with the negative amps but I do have the wire coming from the alternator hooked on the plus side.

Guess I'll buy some new 10 guage wire. Any ideas what I have now? Thanks.

Bob is very correct if there are any alternate paths around the amp meter they are wrong. The starter motor (and possibly an ignition resistor bypass hooked to a 4 terminal starter relay) are the only things not going through the Amp meter.
The key "hot" should be connected to that + side of the meter. Jim

Thanks Jim and Bob. I will change the wiring and put the key switch hot on the positive of the ammeter.

Queston though. Now that it appears the alternator has 2 spade terminals, is it required that I wire it according to Bob's diagram with the doode? I can do it but I wonder why it wasn't done before when they installed it.

Thanks.

If the alternatopr is a stock 10SI Delco as in the illustration,it is necessary to hook up the exciter wire, and the sensor wire as shown. If it has been charging, or has a blanking plug in the terminal slot on the edge, then it is probably a true One wire systen, and the regulator has been modified, or replaced by the rebuilder to create a one wire system. Do not attach wires to the spade terminals of a one wire alternator smoke signals will be sent. Jim

Thanks. I've been reading threads and looking at diagrams on this site for a long time and somehow had the idea that only the alternator wire went to ammeter + and only the ammeter - wire hooked to the starter main post.

Guess I'll buy some new 10 guage wire and terminals to redo some of that when I pull the wheel and dash this weekend. I'll check the ammeter posts as well since the negative amps doesn't read right. I'm sure I have the alternator hooked to the post that is on the same side as the plus/right side as you read the guage and the starter wire is on the left/negative side of the guage. But then if the load wire goes to the ignition switch from the gage + terminal before it would show a discharge with lights on and engine off, then I have it wired bass ackwards.

Guess I'll try to see if that is a 10si or not. Can't read anything but Delco-Remy. It is close to Bob's pic but below the "1" spade there is an "R" and below the "2" spade there is an "F". The mounting bolts are 90 degrees off from Bob's pic. Guess I'll try to get a pic to post. I know the voltage went from a moving 40-42v to a steady 15v when I shorted the #1R to the case and got a spark. Hope I didn't burn anything out. I can add a wire from the alternator to the key switch later without pulling the dash.

I switched wires on the ammeter and put the key switch hot wire on the post with the alternator and now the guage showed positive charging amps for a while. Headlight switch brought it down but still positive. After a few minutes it didn't show much of a charge.

Have to look at my voltmeter to see why it only reads just under 12v when charging. Maybe it needs to go to that ammeter post with the alternator as well unless they sold me a bad one. The headlights will pull it down to 8v.