18 volts at the battery- Help...

[kxnomore]

I just hooked up a new front wiring harness from Classic Parts and now I've got 18 volts to the battery. Does anyone know what may have gone wrong?

The truck has an alternator, and I hooked up the blue/ white double connector to the back of it. Then the red wire, of course. And there was a black wire that was disconnected before and hanging loose, so I duplicated the same thing this time, too. So the black wire that is taped to the other previously mentioned wires is not hooked up. Could that be it?

The voltage regulator was hooked up before and is hooked up now too.

Plus the truck just started running really rough. I mean shaking like an earthquake rough.

Thanks in advance.

[RustyParts]

18 Volts with the engine running or shut off? If you have 18 with the engine running the charging system is out of whack. I couldn't imagine a battery producing more voltage than it's rated at.

Sounds like the alternator is connected correctly, and I really don't know what the black wire could be.

The rough running engine is either a really bad vacuum leak or several plugs are fouled.

Sorry I couldn't provide much help.

[cdowns]

black wire is ground for the alt

[kxnomore]

This was 18 volts running, 15 volts just after shutting the engine off.
So should the ground wire be hooked up to the back of the alternator, or to the brackets then?

Would that cause the high voltage, too? I could run home at lunch and hook it up, but I'm not sure where the ground should be attached.

Did these trucks originally come with generators, or alternators?

[wibilly]

sounds like your voltage regulator too a crap if not repaired your battery will boil over. ask me how i know

[kxnomore]

Originally Posted by wibilly

sounds like your voltage regulator too a crap if not repaired your battery will boil over. ask me how i know

Ouch. I'm taking your advice and just picked up a new regulator. I also got some good advice from American Auto Wire (they build the Classic Parts harnesses), and will also be installing new 3 amp fuses in the guage wires.

He said that's probably why my guage isn't showing the high charge condition.

I'll post the results once I figure out if that's the fix.

Thanks for your help!

[ERASER5]

Is your alts two wire connector a square plug or a flat plug? The square plug is an Externally regulated alt the flat plug is an Internally regulated alt. If and Internal type alt is wired to an External regulator, the result is very high output voltage. A lot of "new" wiring harnesses are built with the newer Internal type alts and you said that your external regulator was hooked up. At the very least, it is a quick check as to the shape of alt connector.

If your connector is square,indicating an external regulator, your regulator is fried or the voltage sense wire is not connected.

If your connector is flat, indicating an internal regulator, switching is simple and fast. You can make it pretty with and aftermarket plug, but this will get you going.
1. Unplug the external regulator.
2. Get four female spade connectors and two pieces of wire. 16ga will do.
3. Make two jumper wires about 2" long.
4. Start at one end of the regulator plug and plug the jumper wire from 1 to 3 and 2 to 4. It is the same forward or backward.
5. Because of the previously mentioned flat alt connector is already installed, your done.

The FAQ has afew threads on this topic for further information. Good luck.

[kxnomore]

Originally Posted by ERASER5

Is your alts two wire connector a square plug or a flat plug? The square plug is an Externally regulated alt the flat plug is an Internally regulated alt. If and Internal type alt is wired to an External regulator, the result is very high output voltage. A lot of "new" wiring harnesses are built with the newer Internal type alts and you said that your external regulator was hooked up. At the very least, it is a quick check as to the shape of alt connector.

If your connector is square,indicating an external regulator, your regulator is fried or the voltage sense wire is not connected.

If your connector is flat, indicating an internal regulator, switching is simple and fast. You can make it pretty with and aftermarket plug, but this will get you going.
1. Unplug the external regulator.
2. Get four female spade connectors and two pieces of wire. 16ga will do.
3. Make two jumper wires about 2" long.
4. Start at one end of the regulator plug and plug the jumper wire from 1 to 3 and 2 to 4. It is the same forward or backward.
5. Because of the previously mentioned flat alt connector is already installed, your done.

The FAQ has afew threads on this topic for further information. Good luck.

Thanks for the advice. I do have a square gray plug in the back of the alternator. It has a blue and white wire going to it. The ground wire is not connected, though, as there is no place to put it. I did change the regulator, but the result is still the same. Could my externally regulated alternator have been "converted" to an internal? Maybe my plug is square, but somehow it was converted on the inside? I still have 17 3/4 volts when the engine is running. This is starting to get frustrating for something that should be very simple.

[72lb4x4]

Did it have the correct voltage before the wiring was redone?

This is probably getting old, but are the terminals on the connector in parallel sort of like this: || or in a line like this: - -? || is externally regulated as I understand things.

Also, the externally regulated connector plugs into the flat back of the alt, while the internal one plugs into the curved side of the alt. The red wire connects to a terminal on the back of the alt.

You said that you have an ammeter. Is there also an idiot light on when the key is on, but the engine off? Does the ammeter needle move in any direction when the key is on, with the engine running or not? It should go in the - direction with the key on, and in the + direction with the engine running.

Try measuring the voltage with the engine running on the AC scale of your meter. I think a reading of 45VAC or so suggests shorted diodes in the alt.

Try grounding the ground wire at the alt to the alt bracket. Use the jumper mentioned in the next paragraph.

Make a jumper from #12 or #14 wire about 6 feet long and 2 alligator clips. Check grounds by measuring resistance from the - batt terminal to the regulator ground, the alternator case.

Looking at the regulator, the connector may be labeled F, 2, 3, and 4. The F end of the connector is supposed to be keyed. With the ignition switch on, in theory, the #4 connector should have 12VDC on it.

The #3 connector should have 12VDC from the battery all the time.
The #2 connector looks like it should have DC voltage from the alt when the engine is running.

No movement of the ammeter with key on, engine off suggests either something wrong in the ammeter circuit, or your new wiring harness is different than stock.

No voltage at the #2 terminal of the reg suggests the fusible link near the battery is cooked. But if the link was fried, nothing would get voltage, so the truck wouldn't start.

No voltage at the #4 terminal of the reg (key on) suggests the circuit between the ignition switch and regulator has a problem. This circuit includes the ammeter...

I think the color wiring diagram post is in the faq. That has enough to troubleshoot the alt and reg wiring.

This is all from the manual and wiring diagrams in there, not from experience, so call me a moron if I'm off base...

[kxnomore]

Thank you very much 72 for the suggestions!

Okay, my alternator plug terminals are like the l l way. They do go into the back part, and not the curved part. I grounded the black wire to the clamp bolt finally.

I have 15 volts to the brown wire on the regulator only when the key is on.

There are 15 volts to the red wire all the time.

unfortunately none of my guages work..

I do not have any AC voltage while the truck is running. The latest readings were 15 volts off and 17 volts running.

I did double check each connection with another voltmeter, and it read the same voltage. Maybe this is just the way it's meant to be? I'm afraid if I don't have two bad voltmeters this one is beyond my mechanical ability. If I can get it to a mechanic I'll post again what the problem turns out to be. (if there is one, as it is running good lately).
I think this is just the way it is going to be.

[72lb4x4]

Unfortunately I don't think the battery will survive this way for any great length of time.

The battery must be pretty overcharged to stay at 15VDC. Its supposed to charge at about 14.5VDC and be around 12.5 with the engine off.

What's on the white and blue wires at the reg or alt? Check both ends to verify that they are the same, meaning there's a connection at both ends.

It probably won't help, but you might try leaving the lights on for a while to drain off some excess charge.

The mechanical regulators are meant to be adjusted, but I'm not sure if anyone actually does it any more.

[kxnomore]

Not sure what you mean by what's on the blue and white wires.

They did not have any voltage one way or the other. do you think this is a wiring problem, or a component problem?

I could get a new alternator for $40, if that could be the problem, but I've heard that it either works or doesn't, never too much or too little???

[72lb4x4]

I meant the voltage on the blue and white wires. Measure each of them to ground (not between them). Also check at the reg and the alt in case theres a break in the wires or connectors.

The alt can be bad and still create voltage if one or more dides is shorted. It sounds like the reg needs adjusted to me though.

I found a typo in my manual that was confusing me, so it makes more sense but it says to connect a .25 ohm resistor between the junction block on the fender and the wire feeding the 12V to the truck. I'm not sure what it will do without it, but .25 ohms isn't much. On the other hand, its a 25 Watt resistor, so its there to limit current. Do the following at your charging systems risk.

The manual says do the following with the engine running:

connect a voltmeter to the batt,
run the engine at about 1500RPM
disconnect the connector from the reg,
remove the reg cover,
reconnect the connector on the reg,
adjust the screw on the reg by the corner of the reg on the opposite end from the connector until the V-meter reads 14.2-14.6VDC,
continue running the engine for 5-10 minutes,
disconnect the reg connector and reconnect it,
check the voltage again to verify its between 13.5 and 15.2VDC.

The manual also says do not under any circumstances adjust the nut on top of the regulator (even though in the pic it looks like it wants to be turned).

It looks like the disconnecting and reconnecting the reg connector is just to keep from shorting the reg, but you say you don't have any voltage on the blue and white wires, which seems wrong.

There's another adjustment for the closing voltage of the field relay (in the reg) but its a bit strange, even though a symptom is no V on terminal 2.

[kxnomore]

okay, now I'm really confused. Not because of your questions, but by the results.

Engine off-
Off- Blue and white wires (and red) = battery voltage (15 volts).

Then running- blue- fluctuating wildly between 12 and 14 volts.
white- steady 9 volts.

red- 18 volts.

turned it off-
blue- 0 volts
white- 0 volts.

wtf!!!
I'm thinking I need a new alternator for sure??? at least then I have all new parts. harness, reg, alternator, battery, etc.

[72lb4x4]

I'd guess that if you let it sit for a while it'll go back to all 15V.
I think the variation is from the reg not the alt.
Did you adjust it?

[kxnomore]

Problem Solved!!!

Bad regulator. I ran the battery down to 12 volts and got a new Borg Warner $30 regulator.

This time I completely disconnected all the battery and charging wires, hooked up the regulator first, the alternator second, and the battery last.

Started it up and got 14.6 volts running, 13 volts off.

Thanks to everyone for your help. Saved me a sure trip to the mechanic!

[olyeller70]

Also check for hidden fusible links. Last time I saw this it was on a 68 Firebird, it had a fusible line behind the fusebox.