Diagnosing charging system health '70 Barracuda EFI

[YellowThumper]

You have already proven there is more load than the alt can handle at idle so if you get caught in traffic you can run the battery dead & fairly quickly too as you have proven  , so My belief is you need to upgrade the alternator output to keep up with the load wether you modify the stock alt as Wild suggests or change to a high output one you will have to do it  , I have run into this a few times now with modern upgrades !
  You absolutely still need the bypass especially if the alt can produce more than 60 amps as the ammeter gauge cannot handle more than 60 amps & the connections through the bulkhead do not like 60 amps either .

I can see a new alternator in my future. I'm curious about this bypass test with 8ga wire. Can I just temporarily connect the 8ga wire from alt stud to battery to test voltage?  I had to read up on what a fuseable link was - didn't know. For this test, can I not use a link?

If "stealth" is not an issue for you, you could use an inline mega fuse. They 100, 150, 175, etc. Amp ones. That is what I have used.
As for test without one. I cannot recommend you to but will say they are for the what if scenario. You are adding significant improvement on capacity with out currently improving output.  So....
I have tested without.

Mike.

[Chryco Psycho]

You have full battery power at both ends of the bypass so I am not sure why a fuse is needed , if it shorted both ends would supply power

[Mopsquad]

Thx everyone!  I've learned quite a bit just from this thread.

[xx88man]

 @Shoooter

[7212Mopar]

Great info. I think I am looking at the same problem with the EFI, MSD 6AL added to the car. I got good voltage 14.3 v at the alternator but dropped a volt at the battery. May be the battery is old?

Please post update when you are done.

[Chryco Psycho]

Check the bulkhead connections or install a bypass wire from the alt to start relay

[7212Mopar]

I already done the amp meter bypass. 130 amps alternator and 6 gauge bypass wire with fuse should arrive tomorrow. All bulkhead electrical connectors were cleaned, inspected and added dielectric grease. I was wondering if my battery was dying from old age until I read this thread. This all started after installing the EFI and MSD systems. 

[Chryco Psycho]

 

[Mopsquad]

Hi everyone, Changed the alternator and now reading a healthy 14.5V or so.  Using the Quality Power 150A.  Took some mods to clear the hemi's head, but made it work.

[Chryco Psycho]

That is great news