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Discussion Starter #1
I have a Powermaster CS130 140a alternator (wired as 3-wire) on my 67. It is part of a Vintage Air Frontrunner serpentine belt system. The last couple times I have had the car out, it charges fine(14.5 at alt post) at start up...until it warms up I leave the driveway... Then the voltage drops to 12v or below at the alternator (10 at the gauge).

The charging system is wired as follows:

Keyed wire to the alternator from ignition
Sensor wire from alternator to horn relay
Wire from alt main battery terminal to horn relay and then to the battery.

Everything seemed to be working fine. Connections seem to be clean as they were assembled just last summer.

Alternator tested good at the parts store...

Not quite sure what to make of it... I would appreciate suggestions...!!
 

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A picture is worth a thousand words...

130alt wire.jpg
 

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Discussion Starter #4
The alternator is internally regulated..

That pic is essentially how I have it wired up...

Cant figure out what is causing the drop off... guess Im gonna have to tear into the wiring.....
 

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Yes, and you did the wire mod at the external regulator, correct ?

Have you had it checked at the parts store ? I have them do it before I leave with a new/rebuilt one anymore.
 

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Discussion Starter #6
My car doesnt have an external regulator on it.
This was a Powermaster alternator. It was checked at the parts storetoday. They said it checked out fine... I put it back on.. and it was doing the same thing...
 

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Check your connections and grounds. Make sure the horn relay buss bar is not rusty.. I like the MADElectrical.com upgraded charging system. I have it on my 68 and a 72 truck and it works great. Way easier to add accessories to, add relays for MUCH brighter headlights, etc.
 

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I wired mine up decades ago.. before internet, internal reg.
Something like this
By passed horn relay etc
Wire from battery thru junction/ fusable link direct to the alternator.. less joins less trouble
Jumper on the back of the alternate from there to the feed terminal to activate the coils
(which is where I think your problem is assuming u dont have a diode out/ dry solder link or similar internal problem)
And the dash light connected appropriate terminal on the alternator
 

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You said:

It charges fine(14.5 at alt post) at start up...until it warms up I leave the driveway... Then the voltage drops to 12v or below at the alternator (10 at the gauge).

then

Alternator tested good at the parts store

then

It was checked at the parts store today. They said it checked out fine... I put it back on.. and it was doing the same thing...

So I wonder if when it's cold, when at home and at the store being tested, that there is an internal connection that is good but once heated up, this connection goes south ?.

I don't know how this might affect things but years ago I had an alternator that was not charging as it should, put in a new voltage regulator and all was well for a time then it went out again. I replaced the regulator inside a second time but this did not correct things so then I took it apart to figure things out and it turned out to be the stator windings were grouped together and connected together with a crimped on connector. If I remember right there were three groupings of these stator wires going to three spots on the regulator. Anyway, the stator wire is a bell type wire and by wiggling the crimped on connection I saw an intermittent connection with my ohm meter. I then took off the crimp connector, sanded the bell wire to get to nice clean copper wire, crimped on a new end, then soldered it and that was the last time that alternator ever gave me a problem.


Jim
 

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I'm more inclined to think when cold, choke uses fast idle so engine rpm's are high enough to "excite" the Alternator to charge, but at curb warm engine rpm's the idle not enough RPM to excite to charge.
 

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Discussion Starter #12
I messed with the car again today... paying closer attention to everything. I noticed that the voltage drops from 14.5 to under 12 when the engine hits 2000 rpm. Voltage returns to 14.5 when the car returns to idle. Seems to get worse as the car warms up.

I yanked the alternator off and sent it back to Powermaster for test/repair since it is still under warranty. It will be interesting to see how it turns out.

The car is wired as suggested by MAD... minus the headlight relays and the remote starter solenoid. I plan to double check everything and swap in heavier wire while Im at it....
 

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So I wonder if when it's cold, when at home and at the store being tested, that there is an internal connection that is good but once heated up, this connection goes south ?.
Yeah I tend to agree with u.... as in my post above I did say assuming all the joints are good ....
yep possible crimps on feild coils..
but more likely/ common to be a dry solder joint on the internal regulator diodes.... they warm (get quite hot actually hence the heat sink and fan on the front) up, crack in dry solder joint opens.. in effect a diode drops out...voltage drop.. just as if a diode dies fault.
If it is, it is very likely that the diode being effected will die in a yr or so time...

This dry joint thing is same fault as in a starter.. the header heat sink myth... start works fine.. go to the shops for milk, starter clicks... big current, causes dry joints on the starter armature....cools down and fine. The heat is due to the very high initial currents going thru... not heat from the headers... dry joint caused by initial being too far advanced and the initial current draw extremely high, over time dry joint.

So get them to swap out the internal regular diode assembly....
Would lay odds that will fix it

Oh to test a starter armature . one puts the armature in a oven and heats up till just too hot to hold.. then drop in a growler or check continuity with ohm meter
Checking continuity with regulator diodes doest work because they are set up as a bridge.. to do so the other diodes need to be unsoldered 1st.. sort of defeats things lol
So its just a matter of going around and re melting all the joints.
 

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Did you replace the wire from alt to battery (or to starter) with a thicker gauge? If you are running a 140 amp alt. your main alt wire needs to be at least 8 gauge, or more likely 6 gauge.
 

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Discussion Starter #15
It is a 140amp Powermaster. Wire to battery is 6ga. It has been working fine until a couple weeks ago... Hoping to hear back from Powermaster this week...
 

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Discussion Starter #16
So... it turns out that something inside the alternator came loose was causing it to function incorrectly. Powermaster sent me a replacement alternator without hesitation!! Slapped it on the car today... and all is well...
John at Powermaster was very knowledgeable and great to work with. Its great to deal with a company that stands behind it's product...!!!!
 
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