Electrical gremlins. 77 J10

[Grand_Wag_85]

Just bought back an old 77 J10 Golden Eagle I owned a long time ago. The truck has been parked since about 2011.

Went on a 600 mile road trip and at the halfway point I noticed the ammeter needle wiggling at high speed right around 0.

Stopped for a few hours and noticed the ammeter showing a drain after I got rolling again. When I let off the gas the ammeter showed about a 1/2 way charge for a few seconds then back to discharge. Did this about 3 or 4 times before it completely went to discharging without coming back.

Swapped the voltage regulator and it began charging normally again. About 150 miles down the road the needle starting fluttering again but no other adverse affects. When it got dark I noticed the dash lights and headlights were puslating in tune with the needle fluttering.

Made it home just fine, alternator and VR are both new. Any idea what would cause the ammeter needle to flutter? What about the dash lights?

[BCRAWLER]

Diode in alternator?

[tgreese]

Dodgy ammeter? Old ammeters are dangerous. They tend to cause dash fires. Lots of discussion here about replacing the ammeter with voltmeter.

Not restricted to Jeeps - http://madelectrical.com/electricaltech ... uges.shtml

What I suggest to get the charge wire out from under the dash:



Above is factory wiring, below is after modified.

Also look here - http://www.ifsja.org/forums/vb/showthread.php?t=184890

[Grand_Wag_85]

Tim-

Usually one of the first things I do is get rid of the ammeter or bypass it altogether, haven't had time yet....Guess it's time!

Any pros or cons to going to a GM 1 wire ALT while I'm in there? Should make for less wiring under the hood.

[tgreese]

The '77s with a 258 came with the 10SI Delco 3-wire. You could copy the factory wiring diagram from the TSM and have the Delco alternator that way. Note the 258 Delco and 360 Motorcraft alternaor schemes are mixed together on the same sheet. They are labelled - you can tell them apart pretty easily if you keep that in mind.

I'm not a big fan of the 1-wire alternators. Maybe I've been brainwashed by this article - http://madelectrical.com/electricaltech ... wire.shtml

If you look at the factory scheme, you'll see that the sense wire (95 RED 14) goes right back to the charge wire (12 RED 10) once you eliminate the ammeter, so that's really easy. You have only one additional wire to add (78 BLK W/TR 24, 10 OHMS) which is the exciter wire. You need a resistor or resistance wire (a 24 ga nichrome resistance wire from the factory), or an indicator bulb, or a diode in this wire path to keep it from back-feeding into the ignition when you shut the engine off. On my J10 I used a diode, and on my J20 I took over the existing alternator light in the dash with an incandescent bulb in series with the excite wire. Not difficult, and the factory-style alternators are available widely and cheap from your local parts store. Mad Electrical also has an article about getting the alternator you want: http://madelectrical.com/electricaltech/delcoremy.shtml

Note that the 6-cylinder CJs had both of these changes - a voltmeter instead of an ammeter and a Delco 3-wire alternator. The under-hood wiring for these is almost the same as the FSJs, so looking at that diagram may also be helpful. Jeep eliminated the ammeter in the CJs in 1975; not sure why they carried on with the ammeter in the FSJs for so many more years. Maybe costs of designing a new dash with a voltmeter? The ammeter in a CJ is a 2 1/8" Stewart-Warner type and easy to swap out for a voltmeter with the size and shape.