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Electrical disaster

Printed From: The CJ2A Page
Category: CJ-2A Discussion Area
Forum Name: Tech Questions and Answers
Forum Description: CJ-2A technical questions here
Printed Date: 24 June 2019 at 2:15pm
Software Version: Web Wiz Forums 12.01 -

Topic: Electrical disaster
Posted By: Dutch 1960
Subject: Electrical disaster
Date Posted: 14 Mar. 2019 at 9:35pm
Getting the CJ2A together after buying it in parts 20 years ago and storing it away.  As part of getting it going, I replaced the coil (with internal resistor), points, condenser, and plug wires with new.  Hot wiring the engine directly to the battery, the thing fired up like a champ, on a single turn of the starter, hot or cold.  The engine and the old carburetor seem to play very well together.

OK, time to wire up the thing for real.  The old wiring loom was chopped up and a real mess, so I moved the wiring loom and regulator over from my CJ3B, "running when parked" some years back, with a nice Brazilian manufactured wiring loom from the nineties, clean and tidy.

What may have been my downfall was leaving out the Ford old style starter relay from the 3B, as various diagrams showed things being wired to the 3 wire Delco alternator with the regulator but not the starter relay.

I recycled the Delco 3 wire alternator that came with the 2A, as the identical 3B alternator and bracket didn't fit right, so the alternator is an unknown quantity.

So after wiring things up for real and hooking up the battery, then trying to light off the engine, I got an engine fire. The ammeter pegged at over 60 amps on the plus side when I turned the ignition key on, and the wire that burned was the one connected to the #4 blade of the regulator, the positive side of the coil, and the ignition switch.  The wire was destroyed at the regulator end of things, melted the insulation up to the coil and through the firewall, and got a bit toasty from there to the ignition switch.

I may be leaving out something important, but I don't want to go on with page upon page of maybe irrelevant detail.  I want to find out two things, if possible.  One is what was the screw-up?  I was careful to multimeter all leads so that nothing got crossed up or improperly shorted out.  Two is what do I need to replace now?  I figure the engine room end of the wiring loom is a goner, along with the regulator and the coil.  Anything else I should check?  Is my vintage ammeter gauge likely fried? 

Any ideas or help would be very valuable to me.  45 years of working on this stuff, and I have never burnt things up before.  Very frustrating and humbling.

Posted By: willyt
Date Posted: 15 Mar. 2019 at 8:07am
Sounds like a mismatch between the alternator and regulator. Is the alternator 6 volt or 12 volt? Is the alternator self regulated? You will need to id the alternator so you can verify the correct regulator and the wiring, if any, between the two.
I would clear all the wiring from the charging circuit and then reconnect one circuit at a time in search of the problem. 

1952 CJ3A (Lil'Green)
early M38A1(Ole Green)
1970 Jeepster Commando

Posted By: Dutch 1960
Date Posted: 15 Mar. 2019 at 9:50am
Could be, but I am thinking I have a fault in the regulator.  The #4 lead is a small diameter wire, likely used to monitor the voltage at the coil, so should not be carrying a big electrical load.  The wire burned from the regulator end, and that lead should not be sending juice to the coil, it should be monitoring the voltage at the coil.

I have always treated voltage regulators as “plug and play”, rather than think too hard about how they work.  But that fried light gauge lead has no business carrying a heavy electrical load from the regulator.

The regulator and the alternator are both 12 volt, but they are old.  I’m thinking about getting a new regulator now, and going to a one wire alternator if there are still issues.  One step or the next should likely eliminate the problem through a process of elimination.

Thanks for the response willyt 

Posted By: Stev
Date Posted: 15 Mar. 2019 at 11:04am
Dutch 1960,

If you do go to a one wire alternator you should consider putting a fusible link into the system.  


1946 CJ2A Trail Jeep, 1948 CJ2A Lefty Restored

Posted By: Dutch 1960
Date Posted: 15 Mar. 2019 at 11:45am

I should have had one in there all along.  The regulator has one on the heavy #3 input wire from the alternator, which didn’t fire off, as that line was not overloaded.  Kind of blindsided by the #4 wire going up.  I will definitely fuse the main power input to the wiring loom (which has always been my standard operating procedure on other projects) and the #4 regulator wire with an in-line fuse if I stay with the 3 wire alternator..  I plan to segregate out the main ignition, fuel gauge and horn wiring from the lighting (which will stay in the existing loom), and rewire.  The power main to the ammeter + side needs to be fused.

Posted By: otto
Date Posted: 15 Mar. 2019 at 8:38pm
Are you connecting an internally regulated alternator to an external voltage regulator? Sounds like trouble to me. Check out MAD Electrical on the web. He helped me out a bunch.

47 CJ2A
48 CJ2A
Forgive me if I don't return the "jeep wave", I need both hands on the wheel!

Posted By: Dutch 1960
Date Posted: 15 Mar. 2019 at 11:34pm
nope, it is a Delco 3-wire, "R" and "F" clearly cast in the metal next to the two wire leads that go to the regulator.  MAD electrical is a good site.

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