After start, will not charge until revved past 3k RPM

[kamzcab86]

but the battery light should be illuminated when the key is in the ON position and the engine is not running. Simply because the alternator is not turning and not charging the battery.

Precisely why I said that since the OP's light is not on when the key is turned and the alternator isn't charging until rev'd up to past 3000, the exciter (aka charging) circuit has a fault somewhere due to the way the circuit works.

Actually the year of the vehicle does matter, as we are aware, there are different wiring diagrams for diferent model years. Even though the charging system operates the same, there may be suttle wiring diferences. Therefore to make sure the correct data is used, the correct diagrams for the car must be used.

Like I said, I am going to research the circuit and confirm it on my cars (both known servicable), since the '87 and '88 use the same diagrams, they should both be the same.

The only difference in this circuit between the years with CE1 panels (1983-1993) is the OXS warning light and counter box (1988+ do not have the light and counter box). All years' charging circuits use a blue wire and is routed thusly:
D+ on alternator > single pin connector near battery > into relay panel at C2 > out of relay panel at A16 > into instrument cluster at pin 12.

Those with OXS lights: The circuit also leaves the panel at D4 and goes to the counter box, which continues to the instrument cluster at pin 10. This is why the OXS light is also on with charging light until the engine is rev'd.

The 1980-1982 cars: The blue wire goes from the D post on the alternator directly to the instrument cluster, bypassing the relay panel (and also ties directly into the OXS warning light). The early cars have a simpler system wiring-wise, but still works the same way.

[nabeelr]

So, I think I found the problem. There is a second thin blue wire that runs from the alternator, and the connecter on it is badly corroded.

When I play with the blue wires connector, with the key in ON and the engine off, the alternator bulb will come on or flicker. If I leave it in the place that allows the bulb to come on and stay on, after a start, the alternator will charge the battery right from the get go. If I disconnect the cable, the alternator bulb will never come on, and after start, charging will only happen if I blip the throttle past 3k RPM.

The way I know it isn't the bulb in the dash is because all the warning bulbs in Cabriolets are LEDs, and there is almost no chance that they will be dead, let alone intermittent.

So that seems to be fixed for the time being, I just have to figure out how to clean or fix the connector.


Does that seem reasonable to everyone else?

[Briano1234]

That is the exciter circuit. It powers the lamp in the cluster. Not all the "bulbs" are leds in the cluster.
Remove the connector from the wire, it is just a ring connector and Replace it.
It attached to the little stud next to the big honking red one.

When you start the car, Key in, the charge lamp will light to say you are running off of battery.
Start the engine, the light may still be on until you "blip" the throttle above 900-1100 rpm momentarily.

This is considered normal operation.

If you have to rev to 3000, before you see a charge, then that I suspect is a failure of the voltage regulator as it isn't correct.

[nabeelr]

Yeah, when the exciter circuit cable is working correctly, there is no need to blip the throttle at all on my car, the battery bulb goes out right when started, and the voltage gauge reflects that the battery is charging.


True, all the bulbs aren't LEDs, but the Battery, Oil, Coolant Temp, Turn Signal, and Shift Up lights are all LEDs.
The only traditional bulbs are the two front illumination bulbs, the clock illumination bulb, and the high beam bulb.
Well, in my 88, anyways...


Well, thanks to everyone for the help! It is genuinely much appreciated.

Now to ask more questions!

[CalAltaDubber]

Actually the year of the vehicle does matter, as we are aware, there are different wiring diagrams for diferent model years. Even though the charging system operates the same, there may be suttle wiring diferences. Therefore to make sure the correct data is used, the correct diagrams for the car must be used.

Like I said, I am going to research the circuit and confirm it on my cars (both known servicable), since the '87 and '88 use the same diagrams, they should both be the same.

The only difference in this circuit between the years with CE1 panels (1983-1993) is the OXS warning light and counter box (1988+ do not have the light and counter box). All years' charging circuits use a blue wire and is routed thusly:
D+ on alternator > single pin connector near battery > into relay panel at C2 > out of relay panel at A16 > into instrument cluster at pin 12.

Those with OXS lights: The circuit also leaves the panel at D4 and goes to the counter box, which continues to the instrument cluster at pin 10. This is why the OXS light is also on with charging light until the engine is rev'd.

The 1980-1982 cars: The blue wire goes from the D post on the alternator directly to the instrument cluster, bypassing the relay panel (and also ties directly into the OXS warning light). The early cars have a simpler system wiring-wise, but still works the same way.

Agreed Kamy, but first rule is always use the correct diagram for the car. He has an '88, so I look at the diagram for an '88, not a '79 or '93. That way (baring P/O hack jobs) I have the correct information for the car. The wiring diagrams also provide information like wire colour including stripes, wire size, pin number, and terminal connection. As you noted the wiring does change with the MY.

[CalAltaDubber]

Yeah, when the exciter circuit cable is working correctly, there is no need to blip the throttle at all on my car, the battery bulb goes out right when started, and the voltage gauge reflects that the battery is charging.


True, all the bulbs aren't LEDs, but the Battery, Oil, Coolant Temp, Turn Signal, and Shift Up lights are all LEDs.
The only traditional bulbs are the two front illumination bulbs, the clock illumination bulb, and the high beam bulb.
Well, in my 88, anyways...


Well, thanks to everyone for the help! It is genuinely much appreciated.

Now to ask more questions!

There you go you found it.
Sorry to take so long to answer, but the blue wire (exciter cct.) is where the battery LED gets powered.
I have confirmed the battery light does illuminate when the key is in the ON position and the engine is not running.

The hi beam should also be an LED, according to the Bently.