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Baffled by BJ8 Ignition light...any ideas?


Freshman Member
Baffled by ignition light...Any Suggestions??

Charging system on My '66 AH BJ8 has me baffled..Following start-up, the Ignition light is barely flickering at 800 rpm (which is OK), goes off at about 1200rpm (again, about as expected) but then as the rpm goes up the light comes back on and gets brighter as the rpm rises (not good!). As a result the battery is not charging as it should.

So my first guesses are maybe new generator brushes are needed, the voltage regulator has gone bad, or a ground is loose.

However, Before yanking and buying a new regulator or other parts (some that I probably don't need) I'd sure appreciate members ideas on trouble-shooting tests to preform, and what to suspect is causing the problem. Thanks to all.

Chuck McB
Country flag
FWIW, the ignition lights on both my BN2 and BJ8 extinguish before 800RPM (and stay off thereafter). They don't flicker much, if at all.

I think there's some troubleshooting procedures in the shop manual (don't have mine handy). Do you have access to a battery load tester? If your battery is more than 5 years old I'd replace it on principle (though I don't think it's the source of your problem). If the generator has 100K miles or more on it it might need an overhaul (again, on principle). The OEM voltage regulator on my BJ8 was good until 170K miles or so. Based on your description of the problem my guess is the generator, but the troubleshooting procedures in the manual should nail it down.


Darth Vader
Country flag
Hi Chuck, The quick answer is all the above. After making sure that you do have tight and clean electrical connections everywhere, I would attack the generator first but I would say don't just do brushes. At the minimum clean up the commutator also. I have some pictures here of my starter which i did over and it is much like the generator. I ditched my generator (running alternator now) because at some time in its life it had gotten so hot that is started to melt the solder out of the commutator. If your generator is like my starter was you can disassemble it easily and clean everything. I was very concerned about the amount of grease and grime that was all thru my windings. I took the windings out and washed them (very carefully) in a water based grease remover then dried them very well in the hot sun for a day or so. Then I painted them with clear coat paint. An old timer told me to paint them with enamel. i said I didn't have enamel but I had urethane clear coat, he said ' that'll work'. Or of coarse you can take it to a pro starter, generator, alt shop. If it is not the generator then I would move on to the regulator. Actually there is a test to determine the regulator or generator issue in the shop manual but I don't have it at the top of my head. So also you could just clean the contacts in the regulator very lightly with something about the grit of 320 sand paper. that certainly might fix everything. But again the shop manual has a very detailed explaination of how to adjust the regulator. I have followed it before in years past to up the charging rate of my generator. You just must follow the directions exactly. Good Luck. Dave.


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Darth Vader
Hi Chuck,
A number of years back, instead of replacing a failing regulator, I decided to install an alternator and purchased a Delco 65 amp unit with built in regulator. After designing a bracket and using a twin 1/2" pulley to extend the alternator in line with the engine pulley, I installed the existing belt purchased less then a year before and in very good condition.

After showing appropriate charging results when initially started and at idle, I took it for a short ride and after 5 minutes the red light shown brightly. Checking, the amperage output was low and my first thought was I had received a bad alternator. After returning the Delco, I purchased a new 105 Amp alternator and after installation and a short drive, the light went on again, I returned this unit for testing and the vendor found no issues and returned the unit. Again, after initial positive charging indications when first idling, a short drive resulted in the ignition light beaming brightly. Frustrated after checking everything without finding anything problem indications I replaced the wire that connected the ignition/ignition-bulb to the alternator and again experienced the same failure.

Returning home from a friend's home a mile away after sunset (battery fully charged with a charger) the ignition light again began to illuminate. Although dark now, I pulled the car to the side of the road and turned off the ignition, Lifting the bonnet and with flashlight in hand, I looked for any out of the ordinary indicator and, moving my hand, I happened to hit the fan. The fan moved rather easily which indicated a loose belt. Arriving at home with the ignition light on, I again raised the bonnet and found the fan still moved easily. Retesting the next morning, I tried moving the fan and it was tight and relatively immovable. Conclusion, a bad fan belt.

Although the original fan belt appeared in very good condition and tight when initially installed on the alternator, it obviously would slip (slightly at first) when an electrical load was applied. This slippage would heat and the belt would expand sufficiently to slip and glaze the face of the belt. When not in use, the cool belt would contract sufficiently and appear tight.

Chuck, check your belt when cold for tightness. After running for a short time and with the light on, stop the engine and check the belts tightness again ... try turning the fan by hand.

Good luck,
Ray (64BJ8P1)


Freshman Member
Thanks Bob. The belt looks pretty snug, but I will check it again...appreciate you taking time to reply.



Freshman Member
Thanks Ray. I will do that first...right now. If it is a slipping belt...boy...will I feel dumb! Chuck


Darth Vader

Think how I felt after experiencing this issue for a year and buying 3 alternators.

Ray (64BJ8P1)

John Turney

Country flag
Don't get the belt too tight on a generator. They don't have as robust bearings as the alternators. If the belt is ok, but slipping, CRC makes a belt dressing that removes the glaze and gives the belt more grip. Also make sure the pulleys aren't too slick.
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