Charging issues

[406Monte]

I know that this issue probably (hopefully) happened to someone else also. I have a serious charging problem. I am running a 140 Powermaster alt and have a red top Optima battery. My problem is this. If i let the car sit for about 4-5 days then the battery goes dead. But, when i am driving it the Autometer gauge runs at 14.2 sometimes then when my electric fan kicks on it drops to around 13 volts. I don't understand the drop off. I have no heater, a/c, or big stereo components. I only run the necessary electrical parts (pump, fan, MSD,). I am also running a M.A.D. wiring harness. I was told by M.A.D that my 3 wire system should handle everything and hold a constant 14.2 charge no matter what i am running due to the 3 wire system sensing the voltage drop and thus adjusting the charging of the alt.

I have already done pulled all my fuses to see if that finds my draw but found nothing that did. Also, when i hit my brakes my voltage drops off for some reason just a little but i have never seen this or heard of this before. Has anyone else? I am at my last wits end and nerve here someone help me out please. ](*,) :cry:

 

[Doober]

Sounds like your alternator may not be up to the task if he said it should hold the voltage no matter what (being 140A it should run those fans with a minimal drop). Taking it somewhere to have it tested would be the first thing I'd do.

 

[406Monte]

I have had the alt and the battery tested and they both are good.

 

[Goob]

Grounds!
Make sure your engine, body, and frame grounds are correct, clean, and tight FIRST.
All connections must be clean and tight.
If the alternator has a bad diode, it will charge, but not at full capacity, and it can drain power at rest.
Also, all electrical components must be cleanly connected, and your regulator sense wire must be pulled from the system power feed, not near the alternator or battery connection.

I'm betting there is a weak ground connection, and the alternator has a bad diode from the bad connection(s) arcing.

 

[Doober]

If the alternator has a bad diode, it will charge, but not at full capacity, and it can drain power at rest.

This was what I was thinking was wrong. I don't know all the ins & outs of alternators, but I knew there could be an internal symptom that would do this (just didn't know what it was exactly).

 

[Goob]

Disconnect the output wire from the alternator and see if it sparks when you touch it back to the terminal, unplug the regulator harness and try it again.

Best way hunt for a draw is with a test lamp, in series from your power source to your loads, or by disconnecting individual wires at the source and watching for the arc.

 

[406Monte]

If it arks then is the diode good or bad. I have thought that the diode could be bad. I have started checking the grounds and re wiring the accesories to better the system.

 

[Doober]

Checking for the arc is checking to see if you have a draw somewhere in the system, it doesn't really say anything about the diode(s).

 

[Goob]

An arc at the alternator terminal would indicate a load there, most likely the diode(s) bad.
3 diodes and a rectifier bridge, a diode is a one-way check valve for current, it's part of how the alternating current produced by the alternator is converted to direct current. (DC Voltage)

 

[Doober]