Alternator light, still having issues Options

[Ray Warren]

new VR
new ALT
12.6 not running
13.9 running
replaced all fuses
ran wire from batt neg to eng tin
all lights are working (i removed driving lights and just capped off the wires. don't know if this matters)
alt light was bright all the time but since i changed everything it is much dimmer. I know the alt is charging but i can't get that dam light to go out completely.
I have also checked the continuity between the alt housing and the red wire from alt to starter.
The only thing i have not checked is the wattage of the alt bulb.

I'm stumped! (IMG:style_emoticons/default/confused24.gif)

[Dave_Darling]

It is likely you have resistance somewhere in the circuit feeding "switched" power to the light.

You said you replaced the fuse--good. Did you clean up the "fingers" that hold the fuse? Did you clean up the conections between the wires and the fuse block? Did you clean up the connectors at the ignition switch? At the battery?

--DD

[Ray Warren]

It is likely you have resistance somewhere in the circuit feeding "switched" power to the light.

You said you replaced the fuse--good. Did you clean up the "fingers" that hold the fuse? Did you clean up the conections between the wires and the fuse block? Did you clean up the connectors at the ignition switch? At the battery?

--DD

I cleaned the fingers.
Did not mess with the conections on the back of the fuse block.(didn't want to open a can of worms).
does look pretty clean there though.
Light is bright when key is turned on and dim when running so i think that meens that the ign switch is ok. Battery connections are new.
I have read several posts where you refer to fuse#9.
Is that counting from the left or the right?

[Dave_Darling]

Don't remember....

The light is supposed to be on, bright, when the key is on but the engine is not running. Obviously, the dim light when the car is running is not what's supposed to happen...

Rats, i remember a Pano article last year about alternator lights, they gave a short list of things to check when the light did certain things. Anyone remember what those were, or know a resource on-line for that??

--DD

[lapuwali]

The alt light is connected so that one terminal goes to the field post on the alternator, and the other to a source of switched power.

When the alternator is not spinning at all (or not fast enough), current flows from the battery through the bulb, through the alternator windings, to ground. The bulb glows brightly (assuming the battery has a good charge). Once the alternator starts to spin, the field coils energize directly from the alternator itself, so the voltage on both sides of the bulb is the same, so the light goes out.

The light will only light if the voltage on either side changes. If the alternator is putting out too much current (the regulator isn't working), the light will glow. If the alternator isn't putting out enough current (belt slips or breaks, or the brushes wear out), the light will glow. Typically, the light will flash intermittently if it's the brushes.

If the light is glowing dimly, there may be some additional resistance on the switched power side (bad fuse connection, bad bulb connection) OR the alternator side (again, usually bad connections). The alternator may not have a good ground to the engine, or the engine to the body.

The brass or tin connectors used on most European cars of the era corrode over time, requiring you to remove them and really clean them. Just pulling them off and reconnecting them 2-3 times is often enough to scrape off the corrosion. It's these cheesy connectors that cause 99% of all "electrical problems". The British were always the worst since they used the cheapest connectors available, closely followed by the Italians, but once they're 20-30 years old, German parts are also usually toast. This is particularly true of the bullet-type fuseboxes used on most European cars throughout the 70s and 80s. You're willing to buy a new regulator and a new alternator, but you won't touch the stock fusebox? Open it up, remove all of the fuses, label and remove all of the wiring, and really clean all of the connectors with a stiff toothbrush and alcohol. Many mysterious electrical problems will vanish if this is done. Better still, just throw the old fusebox out and replace it with a blade-type fusebox, preferably one with gold-plated terminals. It'll outlast the rest of the car.

[SirAndy]

tranny ground-strap? (IMG:style_emoticons/default/confused24.gif)

[Dave_Darling]

Better still, just throw the old fusebox out and replace it with a blade-type fusebox, preferably one with gold-plated terminals. It'll outlast the rest of the car.

Paging JWest Engineering! JWest Engineering, white courtesy telephone please! (IMG:style_emoticons/default/biggrin.gif)

http://www.jwesteng.com/fuse.htm

--DD