Underdrive pulleys causing major charging issues?

[71Challenger318]

Hey guys. I am fighting a problem with my 71 Small Block Challenger. I wanted to get some input from the body of knowledge here.

Original Issues -
1. No charging at idle
2. Undercharging over 1200RPM (12.9v)
3. Rapid discharge driving around town causing radio to cut out, no signals, etc.
4. Very active amp meter, discharging at any load and riding very high at highway speeds (normal?)

Mods related -
1. Mopar underdrive pulley kit
2. Electric fan
3. Modern stereo
4. Oversized battery (750 CCA)

Actions taken
1. Replaced voltage regulator (done last year because old one melted)
2. Replaced alternator with 65A reman unit (newer style unit)
3. Tested/charged battery - Good

Current Issues -
1. No charging at idle (Charges 13.5+v over 1200RPM)
2. Amp meter pegs or rides high at anything over idle

My thoughts -
1. No charge at idle is because of UD pulley kit
2. Amp meter is pegging because of hard discharge around town at lower engine speeds and high charge rate at higher engine speeds.

What do you guys think? I am thinking I need to ditch the UD kit (which I would hate to do) or maybe go for a deep cycle battery? I suppose I could get an aluminum pulley kit for the dress up factor that does not underdrive? Tell me what you think, I need HELP!

-Jeff

 

[moparleo]

If you have access to another car with same engine without issues, swap voltage regulators and test. If no change, swap alternator without changing pulleys. Believe it or not, this is the way the car dealers would diagnose proglems because they had access to these parts off the shelf. By using the parts from a proper functioning charging system, you will find your problem. A deep cycle battery will only mask the problem. When you say modern stereo system, what does that mean ? Can you disconnect the power from this stereo ? If so, do it before you do any diagnostic work.
Tell us what you find.

 

[Rob C]

I have no charging issue's with my UD march serpentine stuff.

 

[71Challenger318]

I am going to call March tomorrow and see what they say. Maybe I will just buy there kit and sell the Mopar one.

I do not have access to another car that works correctly. If you rev the car up it works 100%. I can't imagine that could be the voltage reg. I don't see any way it can't be the UD kit unless you guys think of something else. By "modern stereo" I just mean it has a CD player in it not the old AM jobby. No gorillas in the trunk or anything like that. The crank pulley is way smaller then the OEM one but the Alt pulley is the same size. I can only imagine it is turning the Alt slower than its minimum RPM for charging.

 

[moparleo]

Ok More info now. I didn't know the alternator pulley was standard and the crank pulley was so much smaller. It sounds like you pretty much know what the problem is. Duh I can't imagine they sold you a part that would not work for you on the street if they new that was the application. Did you get it without the paperwork ? If that is the problem I would take it up with who ever sold you the kit. They should make it right without you having to $pend more dough.
Don't rule out the voltage regulator completely. Regulating voltage is what it does.