Alternator light not on when starting.
 

Hello all,

I have an 83 SC. for the past week, I have noticed that my alternator light on the oil gauge does not turn on when I turn the key prior to ignition. I know that it usually lights up when I did that. Not sure if this is something I should take notice of. It is an indication of an alternator going bad. I'd thought that when an alternator goes bad that the light would light up and not the opposite.

I've also noticed erratic tachometer intermittently. surging from 3k to 6 and back and then would settle down to normal.

Right now, I have no starting problem and the car seems to run good. Then again, I'm hesitant to take it on a long trip. If it's the alternator not charging then the car would eventually die on a long trip. I use it for commuting and it's 11 miles each way. so I am assuming that that is not a long enough drive to totally drain the battery.

Any insight to this observance is greatly appreciated.

Alternator light may simply be burnt out - try swapping it out. Happens all the time.

Pull the bulb and test. Then check for continuity between the blue wire in the dash and the blue wire at the 14-pin connector in the engine compartment.

If the bulb is good and you have continuity then the alternator is likely bad. I just went through this in my car a few weeks ago.

Erratic tach is a sign there's potentially something wrong with your electrical. In my case it was a loose wire grounding out (bad alarm install :)).

I'd check the bulb first, but don't be suprised if your alternator goes sooner rather than later.

One safe check would be to measure the voltage across your battery. Engine off should be around 12 (12.6 for fully charged battery). Engine running you should get over 13V. If you aren't, your alternator isn't doing its job or you have a short somewhere.

In many older cars, the indicator bulb is part of the charging circuit. If it is not on the car is not charging. Could be alternator, wiring, or bulb if the SC is of the older charge circuit style.

If it IS on the car is not charging. If it is on during cranking and out during operation above about 1000 rpm, the car is charging. (probably)

Thanks for your quick responses.

For an update, I charged the battery overnight and this morning, I check by turning the key to the on position and the alternator light is now on and goes off after ignition as it should.

A little puzzling. I'll just have to keep an eye on this to see if the battery wil need recharging again. I will test the battery voltage with the car off and with it on idle.