Help Diagnosing Electical Issues

[dodj]

Agree with bullit about voltage drops. It is not necessarily one large drop. It can few smaller ones at different connections. When I had an overcharge issue a number of years ago, three places were the culprit. bulkhead connector, connector along the passenger side valve cover (small block only), and the grounding of the vr case to the firewall.
Removing and installing the vr obviously did something, either the connector on the front or the grounding of the vr. To reduce the chance of VR case ground becoming an issue again I replaced the self tapping screws with small bolts and removed the cowl screen to add star washers and ny-lok nuts to the back side of the firewall. I also spent quite a bit of time cleaning the BH connector. Every time you improved the connection you could see the alt output voltage change from a previous reading.

[Cudajason]

   Do you know how to perform a voltage drop test?  I have been searching for a relatable video but most are bench tests with minimal losses. This one focuses on the battery terminal but can be conducted between any two points in a circuit for instance you could put one lead on the + battery terminal and the other to the VR connector with the Blue wire (with ignition in run position) to see how much loss there is total. I believe .5V or less is acceptable. If it's higher you can break it down into smaller segments to see where the problem lies.

  https://youtu.be/3-9oZuX6-Pg

Thanks man helpful as always.

I checked the blue wire at the VR as discussed above and I getting about .7. So not to high.

I checked the connections at the temp sensor, bot for the fan and the gauge.

The fan sensor was under .5. The gauge was like 5 volts. That seems high.

I did pull the gage sensor off quickly and fired it up.

Initallyblooked good, under 14volts. But quicly moved up over 15. So thats not it.



Checked the

[Cudajason]

Well i just checked all the connections under the hood.

Not really sure if this is right. But i disconnected all the bulkhead connections and checked them. Most connectors show full 12 volts. Is that right or should I do it with the connectors on?

I cleaned and checked every connection under the hood, including the battery terminals. Did not help.

[Bullitt-]

 The fact that it seemed normal right after you messed with it may be a clue.
I found a video that blamed an overcharging issue on a bad VR plug. I seem to recall using a tiny flat blade inserted between the rubber & metal connector to collapse the connector a tad to tighten it up.
Otherwise I might suspect a poorly crimped connector or wire that's breaking down.

[Cudajason]

Still have plan to replace the stock alternator to accommodate the draw from the electric fans?

@7212Mopar yeah that is still my plan.  I have the fans and the shroud SO I may as well use them.  Just trying to see if I can get this alt to charge at less than 15 volts first.

The fact that it seemed normal right after you messed with it may be a clue.
I found a video that blamed an overcharging issue on a bad VR plug. I seem to recall using a tiny flat blade inserted between the rubber & metal connector to collapse the connector a tad to tighten it up.
Otherwise I might suspect a poorly crimped connector or wire that's breaking down.

I actually rebuilt the VR connectors last year using only a new rubber plug and all new connectors, not that it means much.  One of the original wires snaped and caused an overcharging issue.  I did pinch the VR connectors last night, no change, still charging at a tick over 15 volts..  I may redo or jump the green wire just to make sure that is not the problem.

[dodj]

With connectors unplugged you will always read battery voltage. Without current flow,  there will be no voltage drop.
Due to your reported symptoms,  I would concentrate on the vr mounting and the connector and the wires to, and from the vr. I might even run a temp jumper from battery negative to the vr case.

[Cudajason]

With connectors unplugged you will always read battery voltage. Without current flow,  there will be no voltage drop.
Due to your reported symptoms,  I would concentrate on the vr mounting and the connector and the wires to, and from the vr. I might even run a temp jumper from battery negative to the vr case.

Thanks @dodj that is my plan, a jumper on the green wire.  I like the additional ground idea, I will try that as well.

Jason

[YellowThumper]

  I believe that 15+volts is to high. I would charge the battery fully with a battery charger and if the situation continues suspect the new VR is bad or the Blue wire that the VR reads the need has poor connections or degraded wires.

Never mind. I just put the old VR back on just to see if the new one was bad. With the old one, reading over 16volts!!!!

Maybe to old one is bad???

I will pit the new one back on and check the wires.  The wires are all new as I redid that part of the harness last year.

I still suspect the alternator is bad. If internally is fried, it will not properly regulate regardless of VR output signal.
~16 volts is full tilt alt will put out unregulated.

I chased same issues. Bad grounds, low signal voltage, multiple vr's and finally replaced alternator.
What I did to convince myself was start engine. @idle it was 16 volts. I then dogged engine rpm down until it almost stalled. With engine rpm way down, charge voltage never dropped off of 16v.

Borrow the offered one. Once on retest the blue wire voltage with full charged battery to reconfirm signal wire is proper.

[Jay Bee]

@Cudajason geez, I just remembered I had this spare alternator. It was working when I removed it from my car and I'm closer than Brad. I'm pretty busy this week but I'll try and find some time to re-install it and test it again. You interested in trying it out if the re-test is OK?

[dodj]

If internally is fried, it will not properly regulate regardless of VR output

Well the alt can't regulate... that's why there is a separate  regulator......
But if it was fried internally.... it wouldn't work at all. Jason's does.

[Cudajason]

@Cudajason geez, I just remembered I had this spare alternator. It was working when I removed it from my car and I'm closer than Brad. I'm pretty busy this week but I'll try and find some time to re-install it and test it again. You interested in trying it out if the re-test is OK?

Thank you to both @Jay Bee and @Brads70 you guys are what makes this place special.

While I appreciate the offers, don't go to any trouble on my account, I have a new alternator coming.  I think I have solved my cooling issue, with the aluminum rad, but I want to use the electric fans, so I need a new ALT anyway. We will see if that is really the problem.

One thing I did notice is that when I turn on the headlights, the volt gauge reads under 15 volts. 

[Jay Bee]

Jason 'cause of the site's slowness feel free to text me if you want re: my alternator.

John

[Jay Bee]

Okay, no problem. Because of this site's issues I didn't get your post before typing mine. What a clusterf@#$%&! 

[Cudajason]

New 130 amp alt came today.  Have ti fiddle with the belt adjustment a bit, but its on there.

I hooked it up using the one wire option, which is really two wires because you have to ground it.

Fired up reading 13.9 volts at idle. The gauge shows lots of movement when you rev it up!

I think that is fixed.

[Jay Bee]

I think that is fixed.

Sure sounds like it