According to the factory wiring diagram, there is a diode located in the wiring harness between the charge lite and the alternator. Does anyone know exactly where it is located?
info: 86 V6 Fiero gt new alternator charging voltage is 14.65 V (high) charge lite stays dimly lit when running.
The 86 Factory Service Manual calls out the location as "In main harness, below rear bulkhead grommet". IIRC, it is on the inside of the passenger compartment, passenger side grommet, about 6" away from grommet. Look for a brown wire with a tape bundle......
bulb on likely means Alt with problems. Alt is new but still check alt for bad alt diodes etc. New and Rebuild can be bad right out of box. Check side plug for iffy wire or connection(s).
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
According to the factory wiring diagram, there is a diode located in the wiring harness between the charge lite and the alternator. Does anyone know exactly where it is located?
The 86 Factory Service Manual calls out the location as "In main harness, below rear bulkhead grommet". IIRC, it is on the inside of the passenger compartment, passenger side grommet, about 6" away from grommet. Look for a brown wire with a tape bundle......
What is the diode supposed to do in the circuit? Is it just keeping voltage going one direction or?
We have a battery drain in our 85GT N* conversion which I believe is the new Caddy alternator. It drains only on the alternator. We have replaced it twice (with the same brand) and it continues to do the same and charges inconsistently at idle...lights getting brighter and then duller. It seems to be more consistent at driving speeds.
Could it be a bad diode in our car allowing voltage to go both directions?
Had same problem with my 86 GT - light glowed but charged ok, diode trio in alternator was bad - part was about $4 at NAPA. To test - unplug alternator & start car - if light is off diode trio is bad.
I don't agree with your test, AL68. That light needs a completed circuit in order to glow. By unplugging your alternator, you are breaking the circuit regardless of what is causing it to glow.
To excite the field and start producing voltage, the wires on the small plug to the alternator must have 12 volts. One wire is always hot, the other wire sees voltage when the key is turned on, via the GAGE fuse cicuit, thru the VOLT meter and CHARGE light. Unplugging the alternator and starting the car will result in a NO CHARGE condition. A diode is simply an electrical check valve. It was not used in the 88's.
Originally posted by olejoedad: To excite the field and start producing voltage, the wires on the small plug to the alternator must have 12 volts. One wire is always hot, the other wire sees voltage when the key is turned on, via the GAGE fuse cicuit, thru the VOLT meter and CHARGE light. Unplugging the alternator and starting the car will result in a NO CHARGE condition. A diode is simply an electrical check valve. It was not used in the 88's.
Iffy side plug or wire to it can stop alt to charge. See my Cave, Alternator Sense
Most often Diodes fail in Open condition and Lamp etc connected to it/them Will Not light. This is why I said above Lamp diode isn't the problem. If diode is shorted you could see negative volts from volt meter across the lamp. (Make sure meter black goes to ground. Don't pull the lamp. Measure at dash circuit "board.")
Diode Trio fails same Open condition most time. A shorted Diode can drain the battery. Call a trio but uses 6 diode... Diode Trio because Three Phases AC from Alt's windings to rectify.
I don't agree with your test, AL68. That light needs a completed circuit in order to glow. By unplugging your alternator, you are breaking the circuit regardless of what is causing it to glow.
Exactally - by unplugging it you eliminate problems in the rest of the circuit from the alternator to the dash light. The glowing light is caused by a partially shorted diode trio in the alternator.
In the Fiero alternator circuit the bulb needs a ground to light, if unplugging the alternator turns off the light the problem is in the alternator. If the light is still on or glows the wiring is shorted to ground somewhere else, the alternator may be ok.
I see what you are saying. I agree that the test indicates that something inside the alternator casing is bad...just don't agree that it zeros in on the diode trio specifically.
