Charging system help

[highspeeddirt]

I'm needing some advice.  Its GM not mopar related. (sorry)  82 GMC,  New alternator, battery and alternator test fine.  It charges great until I start turning on accesories.  Lights, A/C, ect.  It will drop from putting out right at 14 volts to about 12.5 when I turn on the A/C or headlights individually, but If I turn them both on the same time, it'll drop to 11 and continuously drop while they are on,  Eventually killing the battery charge.  I've tried a different battery just for the heck of it and another alternator.  Same result.  I've checked all my connections at the battery, and the starter.  Bypassed the fusable links to test that out.  All lights work, no blown fuses. 
  Any suggestions for me to check?  I'm about to my wits end!   
          Thanks

[MEK-Dangerfield]

UGH,
  I got nothing here, except to ask if at this point GM was putting the voltage regulator in with the alternator too? It just seems something isn't telling the alternator to juice it up. 

  Mike

[highspeeddirt]

Yep, internal regulator. 

[highspeeddirt]

Ok, heres a little more info.  I had autozone use their little crash cart to test.  It showed lower than what "they" thought it should be.  They didn't leave it on long enough for the voltage to go below 11, but last week the truck went through an auction, and they sat in line with the a/c and lights on for quite some time.  When It didn't sell for what I wanted, I went to leave and had to get a jump. 

My sunpro amp gauge will show as low as 10 v, but I did some testing with my multimeter with all readings taken at the battery.  Maybe someone could tell me if these readings are lower than what they should be......

At idle with no a/c or lights on  13.3v

At idle with lights only               13v

At idle with a/c only                   12.35v

At idle with a/c and lights          12.07v

At idle in gear with a/c and lights on  11.89

When I bring up the rpm the voltage does increase, but stays around 12.25v with a/c and lights on. 

[Challenger6pak]

It sounds like a bad regulator to me.  It is not keeping up with the load.  Just because the Alt is rebuilt doesn't mean it is good.  I have had a bad replacement and the frustration from it.  You say this happened and then you changed parts.  Was there a period of time that everything worked after the parts change? If you have a weak battery and a bad Alt. and you change the Alt.  things will work for awhile.  Then because the Alt. is overworked due to a weak or bad  battery it will wear out quickly and quit. Start off with a fully charged battery when you change the alt. to avoid damaging it. My  .
Hope it helps.

[highspeeddirt]

Well I fixed my problem.  Here is the problem......



And here is the fix.....



Dumped the problem last night, and got the fix today.  Works much better now! 

Thanks for the help!

[Challenger6pak]

That will fix it.  LOL 

[pink panther]

excellent diagnosis doctor, and GREAT repair!