Just to be sure, alternator question

[nestorjw]

I have checked all connections and they seem to be good, the alternater and oxs lights turn on when the car is idling, then go off when the car is revved up. What is the next step to fix this, buy a new battery? or get the alternator tested. I read some past posts, but just want to be sure i do the right thing. FWIW the car only has 75k on it so i am not sure if the alt. would already go bad. The battery is some weird off brand that the PO had put in. Where do i go from here?

[autobonrun]

This may not be a problem worth spending any money on. That is, it should come on when the ignition is on, but there should be enough voltage even at idle for it to go off. I've heard of some cars where the indicator stays on at idle. I think this is ok as long as it goes off when you press the accelerator.

The problem is that the voltage at the battery is different from the alternator output voltage. One check is to verify your alternator belt is tight.

Also, measure the charging voltage at the battery when the car is running. There have been other posts that address the correct voltage you should see.

Also read the attached link. It's written for Triumph but the fundamentals are still applicable. I just finished reconnecting my alternator wires reinstalled my fan housing 10 minutes ago. I hope I don't have to reference this article myself. I'll know in about 30 minutes.

http://www.vtr.org/maintain/alternator-overview.html

[304065]

Do a search in the archives and look for "zero-ampere rpm". Warren has posted a procedure for adding a resistor in parallel with the warning light bulb.

You may ask, why is this happening? Juice flows out of the battery into the ignition switch and over to the warning light bulb, which is a 4W in 82-and later cars. Current flows out of the bulb into the D+/61 "Blue Wire" circuit, flows back through two 14-pin connectors on the electrical console, then into the engine wiring harness and connects to the back of the alternator.

The alternator rotor does not have much residual magnetism, and does not include a permanent magnet like "self-exciting" types. So, until there is a voltage present in the rotor windings, no current will be generated in the stator and the alternator output will be zero. So to fix this, current flows into the rotor from the Blue Wire, magnetizing the rotor, which creates a voltage, which is then rectified by the "trio" diodes and fed back into the rotor, and you're off to the races.

So why would the alternator's output be really low at low RPM? Because there's not enough current flowing through the Blue Wire, or because the engine speed isn't high enough. Most people just rev it up a little, and then things should be fine. But you could also add a resistor in parallel with the bulb, to increase the amount of current flowing through the blue wire, providing greater current at low RPM's.

But that shouldn't be a fix for corroded electrical connections in the circuit. The 14-pin connectors have silver pins, which can oxidize, likewise the bulb holder behind the oil pressure gauge can also oxidize. I would clean those first before modifying anything, chances are that is the cause of your situation.

Good luck!

[nestorjw]

The problem has actually gotten worse over the past day, the lights are on most of the time, and I am thinking that the belt may be loose also. Under a bit of throttle it felt like something was slipping? It kind of had an odd feel like it would slip then catch. I will have more time today to look at the possible solutions. Thanks for the help so far!