Weird charging behavior

[RUSH55]

Hey y'all, I made a post in the oufitting section and haven't gotten any bites. Figured I'd make a post here to see if anyone can help with a diagnosis.
-I have a 77 FJ55, that I put a 100 amp Specter Alt in, when the stock one went out. Once I installed the new alt., I had this problem when at idle, the amperage would drop to the bottom of the negative side (on a stock amp meter guage). I hooked up a dual batt. system with an isolator. The aux. batt. runs my winch and aux. lights. Even after hooking up the dual batt. and isolator, I still have this problem. The other part of the problem is that at night, with lights on, and at cruising rpm's (~2000-2500 rpms), the amperage will drop, then suddenly jump up to high on the positive side of the guage, then drop, then jump, ect. until it just feels like leveling out, or staying in the negative.
What I have heard, but not exactly expanded upon, is that the stock wiring can't handle the increase in amps, and develops too much heat or something, causing strange charging system behavior.
I have a stock type external voltage regulator, everything is basically stock except for the 200 amp alt and the dual batt. setup.
Does anyone have any idea what the hell the problem is and what I can do about it?-
Thanks!

 

[atoyot]

Is the voltage regulator working? Is the battery good? Did you use heavy enough wiring? I was trouble shooting a charging problem in my cruiser for a while. Finally turned out to be a bad battery. I would re check all connections and insure wiring is set up correctly. I've heard it's uncommon for these voltage reg's to go bad. What gauge wiring are you running for the Alternator, batteries and isolator? Double check your grounds also.

 

[Gumby]

Sounds very much like a regulator problem. I'd call Spector. They sold you the alternator, they should be able to tell you if you need a different regulator or even if the SOR alternator is internally regulated.
You could use a test light on your field wire at the alternator. If it goes out when the ammeter goes flat and comes on when the ammeter shows charge, then i would suspect the regulator. It is not terribly uncommon for them to go bad. They are mechanical and somewhat prone to failure.

 

[desertdude]

From the SOR catolog
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Why Specter Off-Road Does Not Sell High-Output Alternators

Specter does not offer high output alternators. We have determined that our customer's needs go well beyond a few more amps for extra off road lights.

These days our customer's power needs can include on-board computers, inverters for 120 volt power, high power communication radios, and state of the art stereo systems. Charging systems to support these devices require more than just a different alternator. The entire charging system needs to be modified to match these needs. Typically this requires changes in alternators, regulators, batteries, and wiring to achieve the needed results.

We recommend that customers who need high output charging systems contact a specialist in the industry familiar with custom charging systems. These specialists will help determine your actual power needs. They will assist you in designing a complete charging system including all the necessary components, wiring changes, etc. This avoids the problems and possible damage caused by too many charging amps for the stock wiring or too many amps for the stock amp gauge. Many times these new charging systems require considerable modification of the original vehicle wiring to complete the installation.

So if you feel you need more power, please consider talking with a specialist before just installing an alternator with significantly more amperage output.

 

[dd113]

It really sounds like the regulator. I would replace it just cuz. Buy an aftm amp/volt gauge and hook it up and see if the OEM gauge is working correctly.

 

[Pin_Head]

In the stock wiring, the amp meter measures the current going in and out of the battery and not the alternator output.

It is very unusual that the amp meter would peg on the drain side at idle even if there was no aternator. The only way it would do this is if you had every light and accessory on. If it is pegged w/o all this stuff on, you may have a short or some other chassis drain.

Th sudden changes in the charging suggest either a wonky regulator or a bad wiring connection that is intermittent.

 

[RUSH55]

I'm pretty sure my wiring is fine. But it is the stock wiring for everything but the batt. cables and all wiring for my extra accessories. When I did change the alt and regulator, the reg. took a crap early on, and I had to get another one. Both were stock replacement units from Specter. Maybe someone carries a higher quality unit?