Weird charging

[Knebel]

I apologize for opening a new topic about this, but there is still some weird stuff happening with my charging system. I just cant figure this out.

Brand new 90amp alternator
Electronic voltage regulator
Direct 8ga with 100amp circuit breaker to battery from charging stud
Ammeter NOT bypassed yet

So... when I drive the car in the day, i see a good 13.8volts on my voltgauge. My ammeter is about straight in the middle because most of the current goes through the 8ga directly to the battery. when my fan kicks on, I see 13.2 to 13.5volt. That dosent really change and seems very stable.

Now tonight, I drove the car in the dark with the lights on and when the fan kicks on, i saw about 13volts. It seemed fine but then all the sudden i see the ammeter jumping up to the positive side (not all the way) and the lights get a little brighter (assuming the fan kicked on and the alternator needs to put out more current). That happened off and on a bit with the ammeter going back to middle and then back up, like... cycling on/off something, like...the fan. now the kicker, i see only 12 to barely 12.5volt not increasing when the rpms go up while i drive. Im like "wtf is happening???".

all the sudden, the voltage goes back up to just the normal 13v i saw before with the fan and lights on. I watch the ammeter and its still doing the thing like switching some load on and off now and then but the voltage stays at 13v but later on goes back down.
conclusion, the voltage changing is not parallel with the jump in the ammeter. Whats going on there? Is the alternator just putting out more current to keep up? but why does the voltage drop so low? 12v is waaaay too low in my eyes even when drawing 50amps at idle. My alternator sheet says 57amps or so output at idle.

Edit: the jump in the ammeter seems very hard, like a switch, i verified and it still happens when the electric fan is already on, so it can be that. Can someone explain how the alternator gets excited with the external voltage regulator?

 

[65sporty]

I would be looking at your regulator, you should see about 14.6v when charging. The amp's may go up and down but the voltage should remain steady.

This link is a long read but it should help explain how the regulator works.
Catalog

 

[Knebel]

Very informative, Thank you! I get out of this, that it could just be normal and my battery needs to supplement from time to time. I cant Imagine that im pulling more than 50something amps at idle with the lights on...

Im upgrading to the 70 oltage regulator with the dual field soon, so ill see if that does something.

 

[70bigblockdodge]

A fan and lights are heavy loads you could easy be dragging the alternator all the way down.

 

[Knebel]

Here are some measurements I just took. The Battery is drained a little but thats okay for now.

Engine off, IGN on.
11.95v between Battery + and -
10.64v at Ign ON and Ground (I have a Junction where all the +12V switched ignition goes to and is going to accessories like efi and fuel pump relay)

Engine Running.
14v between Battery + and -
13.5v at Ign ON Junction
14.2v Alternator output and Ground

the .2v difference between alternator output and Battery is not too crazy, what I am more concerned is, where can the voltage drop happen at the switched IGN 12V. I dont have a ballast resistor and have a junction block instead, the blue wire from IGN goes to that Junction and to the voltage regulator. So the voltage regulator sees 13.5v whereas the Battery is 14v when engine running. Isnt the switched IGN source supposed to be the same as the Battery voltage?

My EFI is connected to the Battery and the Handheld reads the battery voltage, this is where it came down to 12v....then 11.9v and then it jumped up a bit again to 12.5v. All while the ammeter independantly showed some more and some less current and the lights got a tad brighter/darker. Almost like a switch which enabeled some more current to be produced and then turned back off. I do want to bypass the ammeter soon...im just not up to tackling this quite yet. But, whats in the path of 12V IGN On? Does that come from the Junction splice behind the das and goes to the IGN switch?
I got the 14v going into the car to the ammeter tho, that checked out good.

 

[Knebel]

Little update, I installed an adjustable voltage regulator (the 70s style with double field) and converted the wiring. started the car, 14.8volts. Turned on the lights and blower motor, 15.2volts. I also noticed an almost .3v drop in the short blue/white wire between bulkhead and my junction block, so I need to put a new wire in there and mybe replace the connector at the bulkhead.

 

[BJS racing]

Make sure you bypass the ammeter and make sure you have not started melting the bulkhead connector. Those are the two weakest points in the car for the main power wiring. Also make sure that the body of the regulator has a dedicated ground. That is the biggest problem on these charging systems.

 

[Knebel]

I have installed a groundwire which wires the regulator directly to the alternator housing. I hd a piece of wire about 6 inches from the bulkhead to the regulator/ballast and that had almost 3 OHMs resistance. I cut that out completely and have the switched 12v blue/white directly to my junction. Just cleaned up the mess a bit and reduced wires. Hope that cleans stuff up a bit.