altenator change?

[moif]

Driving this morning with my headlights on they began to dim and brighten alternatly with my amp meter showing off scale positive. It was pegged. My battery is fully charged and the connections are secure. Driving home with my headlights off the amp meter shows a normal slight charge. Is this an indication of a wiring problem or failing alt, it has 60000 mi. on it. 1987 Caprice Classic LS, 305 eng. All stock. Any particular wires I can check? Thanks for any help.
moif

[silicon212]

By dimming and brightening, do you mean as in overcharging i.e. normal brightness and really bright?

If so, it can be a failed internal voltage regulator. This will require the replacement of the alternator, and fast! You will kill your battery, blow your computer and cause light bulbs to fail in short order.

Now, if you mean it got really dim and then normal brightness, then there could be a ground issue with the headlights. Check all underhood grounds and ensure that they have a solid connection. Tighten any you find that might be loose.

[moif]

Thank you silicon 212,it`s the alt. will r&r tomarrow.

[mike561]

The old fashoned way to check an alternator is have the engine running and disconnect the battery, if the engine shuts off you know the alternator is bad

[j cAT]

Originally Posted by moif

Thank you silicon 212,it`s the alt. will r&r tomarrow.

without using a volt/ohm meter your guessing and this can and usually means unnecessary and sometimes damaging attempts to repair..

with the meter report your findings to the forum and we can give you the correct repair direction..



I have seen defective batteries....batteries that short out....If you place a new alternator on this type of failure its by by new alternator...also you could have bad wires,,,,shorts causing this problem all needs to be checked out with meter...




good luck

[silicon212]

Originally Posted by mike561

The old fashoned way to check an alternator is have the engine running and disconnect the battery, if the engine shuts off you know the alternator is bad

No. This is a very efficient way to KILL an alternator! If it was good before, it might not be good later!

[Chevy59Diesel]

The frame to engine ground strap could be loose. Most times if it is an intermitent problem checking loose wires/grounds could solve the problem.

[silicon212]

Originally Posted by Chevy59Diesel

The frame to engine ground strap could be loose. Most times if it is an intermitent problem checking loose wires/grounds could solve the problem.

VERY good point.