Charge Indicator Light

[Bruce Dorsi]

Crosley's recent alternator thread brings a question to mind.

My wife had a 1974 AMC Javelin, which she purchased new.
....After approx 1 year, the idiot light in the charging circuit came on.  

I tested the charging voltage and it was normal.  The battery never went dead.  ....We drove the car approx 4 years with the idiot light "on."

One day, the idiot light went off, so naturally I began to worry!    

Again, the charging voltage tested normal, and the battery never went dead.  ....We drove the car another year with the idiot light "off."

I have never been able to understand why the light would act the way that it did.

It is possible that the indicator lamp finally burnt out, and that would explain why it went "off," but why would the alternator put out a charge if the bulb was burnt-out?   ....If there was a resistor in parallel with the bulb, then the alternator would be energized, even if the bulb was dead.

So, my question is:

What would allow the idiot light to turn "on," without affecting the output of the alternator?

I have pondered this question many times over the years, and have yet to find an explanation.  ....I guess that's why it is called an IDIOT light!


Can someone please enLIGHTen me?

Thanks for any responses!

[enjenjo]

As I recall, in those days AMC used a Motorola alternator, which was not dependent on the light to energize the field, it was done thought the solid state regulator. Since the light goes off by having power on both sides, one or the other wires didn't get power when it should, so the light lit all the time. so the alternator could charge with the light on. Most alternators with a few miles on them could do this too, the fields sometimes will be magnitised enough to self energize.

Now most normal people would take it in to be checked, a technician would repair whatever the problem was, and go on their merry way. But Nooooo, you had to just keep driving it, being distracted all the time by that red light on the dash.

Did I mention that the temp light on my van comes on just before the thermostat opens, and cuts back to a dull glow for the rest of the ride? Nothing to worry about of course, it's only been doing that for three years

[Bruce Dorsi]

WOW! --- Thanks for the F-A-S-T response, Frank!

As I recall, in those days AMC used a Motorola alternator...

Well, that explains it.  ...I never had a manual for that car, and my only experience was with Delco alternators, so I foolishly applied GM/Delco logic.

   

Now most normal people would take it in to be checked, a technician would repair whatever the problem was, and go on their merry way. But Nooooo, you had to just keep driving it, being distracted all the time by that red light on the dash.

YOU are the first person who has ever accused me of being "NORMAL." --- THANK YOU! THANK YOU!! THANK YOU!!!

[58 Yeoman]

Did you put a piece of black tape over it while it was on?

[47convert]

Did you put a piece of black tape over it while it was on?

Hah! reminds me of my daughter's old Neon - the check engine light came on and stayed that way for months even though the car was in for service and everything was fine. I finally took the bulb out and we forgot all about it. Later she sold the car to a friend who took it in for service and the mechanic replaced the bulb. She had it checked repeatedly for problems after that until she finally had them remove the bulb. Car's still running great.

[model a vette]

I got a '73 Gremlin for free once. My wife drove it for about five years. I think I put about $200 in the car during the five years and sold it for $500. The Motorola charging system was weird for the entire time. Sometimes the light would be on, sometimes not. I installed an ammeter so I could track what was REALLY going on. The system acted like the current one wire alts. It didn't "turn on"  until the engine was revved. I changed both the alt and the regulator and the system continued to work the same way. The light didn't reflect whether the system was turned on or charging. The regulator was a sealed solid state unit so it was difficult to know why it acted the way it did. As long as you revved the engine on startup there was never a problem with a discharged battery.
AMC seems to have always "marched to a different drummer"!

[Dave]

I got a '73 Gremlin for free once. My wife drove it for about five years. I think I put about $200 in the car during the five years and sold it for $500. The Motorola charging system was weird for the entire time. Sometimes the light would be on, sometimes not. I installed an ammeter so I could track what was REALLY going on. The system acted like the current one wire alts. It didn't "turn on"  until the engine was revved. I changed both the alt and the regulator and the system continued to work the same way. The light didn't reflect whether the system was turned on or charging. The regulator was a sealed solid state unit so it was difficult to know why it acted the way it did. As long as you revved the engine on startup there was never a problem with a discharged battery.
AMC seems to have always "marched to a different drummer"!

We actually took a gremlin and wired a ford voltage regulator to the alternator cause the dam electronic external regulator kept giving the owner fits and crapping out. As far as I know the thing worked fine for years after we did it.
Dave

[Dave]

Whats the beastie boys got to do with a light... See
ms your on the wrong board DUDE
Dave