voltage across battery when charging ?

[~The Jester~]

Even if the battery is junk, shouldn't we still get a 14v reading on the terminals when the car is running?

What's the voltage on the battery with every thing disconnected? I mean JUST the battery. I'm still thinking that damn kill switch (SMOKED mine in no time) or a short somewhere.

This is killing me. Now I know how the wife feels when she watches her soap operas. I GOTTA KNOW!

[Mustang_289]

This is always how I've determined whether a battery is failing or not. If 14v across the battery terminals told me the alt is doing it's thing. Then I replace the battery we've done in our stang.

My son and I decided to take the rear battery wiring out of the equation and temporally moved the battery back up front and wired it up OEM style. Same low below 13v when car is running.

[82 GT]

Your're making this harder than what it really is dude.....your PA alternator is shot.........period.
Send it back to be repaired or replaced.....BAM....back in business!!

[82 GT]

So...did you replace that alternator yet?

[Mustang_289]

Yes we did - put a brand new Powermaster 140a alt on, same readings. We haven't touched it since then.

Here's what we've done to date:
* Changed alts with same readings.
* Swapped out the battery
* Relocated the battery to the front, removing these things from the equation:
- 2G wiring to the back of the car
- Ground to the frame in the rear of the car
- Kill switch located in the back of the car
* Checked and cleaned all the grounds
* Reconnected the ground strap to FW

[Joel5.0]

Originally Posted by Mustang_289

Yes we did - put a brand new Powermaster 140a alt on, same readings. We haven't touched it since then.

Here's what we've done to date:
* Changed alts with same readings.
* Swapped out the battery
* Relocated the battery to the front, removing these things from the equation:
- 2G wiring to the back of the car
- Ground to the frame in the rear of the car
- Kill switch located in the back of the car
* Checked and cleaned all the grounds
* Reconnected the ground strap to FW

Following your problem, looks like some checking of the alternator output on the car is recommended....not in terms of voltage but, in terms of amps. I know this is not classic but, a checking of the power output w/inductive clamp is suggested. This to verify that the alternator is indeed producing output and, if it is, then concentrate on whats causing the voltage draw in your car. A short, severe enough to cause the alternator to go full blast in amps, will cause the voltage drop and keep it below the 14.5vdc "all fine" goal. My other 2¢. LUK.......this one is really interesting.

[~The Jester~]

Are any fuseable links invlolved in this equation? If so check/delete them.

Powermaster alts are "1 wire" type, correct? If so, where does that "1" wire connect to? I belive you said the starter solenoid, right? Check for corrosion on ALL the terminals on that solenoid post. Also, no washers between wire connections on there either. Galvanzed washers make good insulators....



I'm still going with my original theory, this is gonna be something "stoopid".......

[82 GT]

This is going to be one for the archives when we find the answer.

[Hozer 88GTConv]

Jester: "Powermaster alts are "1 wire" type, correct? If so, where does that "1" wire connect to? I belive you said the starter solenoid, right? Check for corrosion on ALL the terminals on that solenoid post. Also, no washers between wire connections on there either. Galvanzed washers make good insulators...."

Powermaster one wire hookups go directly to the positive terminal on the battery.
Do you have the two blade terminal hookup for the voltage regulator on your powermaster too? I have the stock green wire going to the upper blade terminal as recommended by powermaster. Nothing is conncted to the lower blade terminal.
I don't want to sound redundant, but was the diameter of the pulley on the alternator ever measured?
I had this problem forever, b/c I switched alternators after I had installed underdrives, so my old alternator had the underdrive pulley, Not the 140 pwermaster out of the box.
I have 14.4volts at idle with a 1 7/8" alt pulley.
my grounds are crappy too, I still have that worthless stock strap from the head to the firewall and nothing going to the frame.
this one is going to be good...

[82 GT]

Originally Posted by Hozer 88GTConv

Do you have the two blade terminal hookup for the voltage regulator on your powermaster too?

Powermaster alternators have a built in regulator. I'm not sure what your're referring to about a "green" wire.
My powermaster has a 2 gauge wire from the alt. to the battery.....nothing else.

[Hozer 88GTConv]

The literature accompanying the Powermaster said to install it that way. I'll get the exact nomenclature and post it...
Believe me, I wouldn't have done it if powermaster hadn't said to do it...it was a pita...

[82 GT]

I still have NO idea what you're talking about. My Powermaster came with no such instructions. I'm not saying I don't believe you; I just don't understand why our alternators are different.
The only extra on my unit was to be able to connect the factory ammeter gauge up if I wanted to.
Maybe yours is newer than mine. Mine is about 6 yrs. old.

[Hozer 88GTConv]

It's the "A" terminal on the voltage regulator pigtail. The green wire is attached to the upper blade terminal on the powermaster to provide field current to the alternator and according to the schematic, signals to "sensors".
I bought mine maybe three years ago?
Here's a pic...I have no idea if this is really necessary, I just followed directions b/c I don't know jack about electricity.

[82 GT]

WOW...mine looks NOTHING like that. I literally have ONE wire hooked up to my powermaster and that's it......from battery to alternator.....done.
Hey...as long as it works.........

[Mustang_289]

I think the earlier powermasters could be wired up one wire, or some of the original wires as well. The one we've got just has one wire.

I'm trying to find an Amp Clamp meter to check to amps being drawn.

[HotRoddin]

Look for an open voltage sense wire ... your alternator isn't turning on ... you are reading battery voltage across the battery. The reason you see the full 14+ volts when you take the battery cable off is likely because thats just the way some voltage regulators work .. it has to do with bias voltages for the transistors in the regulator circuitry.

I got 50 cents says your regulator wire is open somewhere ... check the voltage right at the alternator terminal ... not the connector, but after the connector (could be broken inside the connector).

Forget underdrive pullys ... you eleminated that when you reved it up with no change .. forget a short in the output .. you short a 100+ amp alternator and your gonna have sparks, or at very least a very very hot wire somewhere. The only logical explination left that i can see, is the voltage sense wire, that tells your alternator what to put out ... if it's open and there is no signal getting to the regulator, then the alternator won't put out squat, leaving you with only battery voltage, which at full charge is around 12.6 volts.

Thats my 2 cents worth
Rod

[~The Jester~]

Originally Posted by HotRoddin

Look for an open voltage sense wire ... your alternator isn't turning on ... you are reading battery voltage across the battery. The reason you see the full 14+ volts when you take the battery cable off is likely because thats just the way some voltage regulators work .. it has to do with bias voltages for the transistors in the regulator circuitry.

I got 50 cents says your regulator wire is open somewhere ... check the voltage right at the alternator terminal ... not the connector, but after the connector (could be broken inside the connector).

Forget underdrive pullys ... you eleminated that when you reved it up with no change .. forget a short in the output .. you short a 100+ amp alternator and your gonna have sparks, or at very least a very very hot wire somewhere. The only logical explination left that i can see, is the voltage sense wire, that tells your alternator what to put out ... if it's open and there is no signal getting to the regulator, then the alternator won't put out squat, leaving you with only battery voltage, which at full charge is around 12.6 volts.

Thats my 2 cents worth
Rod

I think we have a winner! HotRoddin, where the hell have you been for the last 4 pages??? LOL

Sounds legit to me, check into it and LET US KNOW!!!

[Mustang_289]

Plot thickens,,,

Just checked the amps coming out of the alt, a little over 20A, tells me nothing is sucking a lot of amps to cause volts to drop.

Currently we've got a Powermaster 1-wire alt on the car, not sure how these alts turn on.

[82 GT]

Originally Posted by Mustang_289

Plot thickens,,,


Currently we've got a Powermaster 1-wire alt on the car, not sure how these alts turn on.

They are self "excited" which means the field windings are not energized until rpms are at about 2500 rpms.
Start the engine and rev it to at least 2500 rpms and then take your readings.

[HotRoddin]

Originally Posted by Mustang_289

Currently we've got a Powermaster 1-wire alt on the car, not sure how these alts turn on.

Well that blows my theory all to heck !!

I must have read the posts wrong ... didn't know you had a 1 wire alt.

I'd rev it up like 82 Gt said, to make sure it's "excited", then turn on all accessories to load it down ... then take your volt meter and measure from ground (make sure its a good ground !!) to the battery term. then to the battery clamp, then to the cable as it comes out of the clamp, then to the first conn. at the other end of the cable, then the conn. to the alt itself ... somewhere you are dropping 2 or 3 volts and you should be able to find it fairly easy.

If you are getting 12.3 volts even at the back of the alt. then measure the voltage between the alt. case and the neg battery terminal ... should be zero ... if you're close to that, then your alt just isn't turning on ... in your case isn't getting "excited" ... a problem i've never had

If none of that gains you any new info then i think it's time for a trip to the local auto electric shop.

Rod