Charging issues help

[beepbeep000]

Hey all,

I'm looking for some advice on fixing a charging/electrical issue I'm having with my '74 RR. Basically, I don't think my battery is being charged when the car is running. Battery is brand new and I replaced the alternator this past weekend to be sure, as well as the voltage regulator. Everything else is brand new as well on the engine - recent total rebuild. Wiring is new as well.

Car starts great, no prob there but when I turn on the lights, the amp gauge on the dash dips down and when I rev it up, it doesn't go back up or stay even. So first, is there a more certain way to tell if there is a problem with the charging system, what's the best ways to diagnose this? Perhaps there is a bad ground somewhere? Thanks for the help.

 

[Mopars & Missiles]

With engine off, voltage across battery terminals should be about 12.8 vdc to 13.2 vdc on a GOOD battery. Old battery might be a few tenths less.

With engine running, voltage across battery terminals should be about 14.0 vdc to 14.5 vdc if alternator is charging. You may need to slightly increase RPM to see this, depending on engine idle speed and type/size of alternator.

If voltage across battery DOES NOT increase, you have a problem with the charging system.


PS. NEW does not necessarily mean GOOD or WORKING CORRECTLY.

 

[Glenwood]

If you don't have a meter, an old mechanics trick was to take a screw driver and place the metal tip against the back of the alternator, in the center shaft while running. If it's magnetic, it's likely charging.
Your gauge wiring could be backwards. Are your headlights dim and brighten when you bring up the revs? A meter is a worthwhile investment...

 

[beepbeep000]

Thanks to both answers. I'll hit it tomorrow and see what I can find. Frustrating to deal with wiring and electrical issues - not my strong area.

And no, the headlights stay the same as far as I can tell no matter the rpm's.

 

[Average Joe]

Check the ground to your engine block. The alternator needs to be grounded well.I just went through the same problem and that what it was.

 

[beepbeep000]

Hey Joe, thanks for the info. I'll check that as well. Good to see another b-body from my old stomping grounds. I lived in Springs/Falcon for 8 years. Good times - grown a lot though. Too many californians

 

[Average Joe]

Awesome beepbeep, I actually went to Falcon high school.LOL Hope your wiring issue is an easy fix.

 

[beepbeep000]

Well, didn't have much luck today. Checked the battery and was only getting 11.75 on it with the engine off - and the same with it on and revved. So evidently it's not charging.

Checked the alternator wiring and not sure what I have frankly. I'm attaching some pics for anyone to look at. The blue and green wires go up to my voltage regulator and the black wire which is also on the back rear of the alternator- what I thought at first was the ground - goes over to the back of the fuse panel (pic 3). There is no other wires off the alternator, no ground wire that I can tell.

So I took the black wire off to attach another wire for a ground and when I did, it sparked and blew a fuse - so obviously there's power to it and it's not the ground. Not sure what exactly this black wire is. I then reattached the black wire, put a new fuse in and the car was back to the way it was in the beginning.

I tried attaching another wire from a different screw on the alternator to the chassis for a ground but it didn't seem to make any difference in the whole charging system/battery issue. Sooooo, where should I go from here? Do I need to run the ground to the battery rather than the chassis?

 

[Glenwood]

Hey beep, the large black wire (12awg I think) is the main power source from the alternator to your system when running. There is no ground wire connection directly to the alternator as the DC- or ground is bonded through the alternator bracket/engine which should have a large wire connected to the battery neg post. This is vital and all of the connection points should be clean of paint and rust. Here's a schematic from a '72 which is similar except the emissions and ignition stuff.
The green and black going to your regulator are shown here.



- - - Updated - - -

Here's a simpler diagram which might help. It's important to make sure the regulator has a good clean ground connection to the firewall also. The bonding strap or wire from the engine to the firewall helps to ensure this.

View attachment 303727

- - - Updated - - -

Here's another.

View attachment 303729

 

[beepbeep000]

Thanks for the diagrams, very helpful. So if I understand you/it correctly, there needs to be a separate ground from the alternator straight to the battery neg? If so, that might be the problem as there is nothing currently like that. I will try that. I have a good connection from my voltage reg to the body so I think I'm good on that.

 

[Glenwood]

No the alternator is bonded to ground by being bolted to the engine provided there is a good connection from the engine to the battery. You can attach a jumper to the alternator housing to test. You may have already fried the alternator when you connected the ground to the batt terminal on the alternator unfortunately.

good luck!

 

[beepbeep000]

ah I got ya. Glad I haven't had time since I posted the last to do anything:hello2: - that could've made things even worse.