sgtskid

So having no voltage a terminal "L" doesn't mean anything then?
My DIC hasn't lit up since I've owned the car which makes following the next part of the troubleshooting guide difficult because it wants me to jumper a wire and see if the indicator lights up.

I currently have the DIC out to check bulbs and determine why it doesn't light up. According the the FSM if the DIC AND gauges don't work then it is the CLSTR FUSE. But my guages work only the DIC doesn't. The buttons for trip/fuel/eng/met all work but they are on a separate circuit.

I swear I hate electronics!

sgtskid

so after doing some more research it appears as though the "L" circuit is merely grounded by the alternator and if the charge indicator doesn't light up the problem is elsewhere. This circuit would not affect the charging status of the alternator.

I believe I may have a problem with the fusible links. I will try and check those tonight or tomorrow night.

AGENT 86

You may want to have a closer look at your 90 manual.
My 86 manual shows that terminal "L" is the field wire, which turns "ON" the alternator.
It gets power from ignition switch through a resistor or resistor wire. Terminal "S" is the sensing wire, which senses if there is more output required.

sgtskid

I'll try to post up a picture tomorrow of the wiring diagram but unless I'm reading it wrong, terminal "L" just goes to indicator. (p.s. it's very likely I'm reading it wrong so someone correct me. Electronics and diagrams are by no means my strong point)

Speaking of which, I did manage to find out why my information center doesn't work.

8a8mfh

I used to convert those alternators to run on older vehicles. I'm pretty sure the L terminal has to go through either a light or a 33 ohm resistor to get the alternator to charge.

So in a stock application you might check that the wire is not broken, etc. Maybe run the L terminal through a resistor to 12 volt temporary and see how it works. I know they wouldn't charge at all with nothing connected to that terminal, and something as simple as a light bulb would make it.

sgtskid

The information center has a broken ground circuit for all the bulbs - I'm guessing that's why it never worked in the 12 yrs I've owned the car. But that would also mean that the "L" circuit has never been complete. I have battery voltage from "F" and "S."

Your saying that it needs resistance on "L" to charge? The latest alternator charges like mad for about 20 minutes (audible noise) and then shuts off. Like it overheats or detects an overcharge. I can shut the car off and come back a while later and it will do the same thing.

Here is the circuit I am working off of.

AGENT 86

Your diagram shows 4 wires to alt. Do you have 4 wires to alt ?

AGENT 86

Did some google of your CS 130 alternator. Didn't find any info on 4 wires to alt, just the fact that "L" is what turns on alt, by getting 12v from ignition via warning light. It seems that the bulb itself is being used as the resistor, so you would need to fix the open in that circuit.
Could be the bulb is burnt or the 5 amp cluster fuse is blown.

sgtskid

Yes, there are four wires to the alternator. 3 are in a harness plug and consist of the "L" "S" and "F". The 4th wire is a larger wire that connects to a terminal on the back of the alternator and runs straight to the battery. (See pictures on page 1)

Fuse and bulb are both good. I have the unit at a repair shop where they are attempting to solder it back together. But again - the DIC hasn't worked in the 12 years I've owned the car so why would it matter now?

AGENT 86

Well, it seems you have the field energized via the 4th wire.
What does your manual say about "L" in diagnostics ?



Good Luck

8a8mfh

Maybe the previous owner rigged it so it would charge with the DIC not working and his rig has now failed. Not going to find that info in a book.

sgtskid

Alrighty, well here's something that I haven't seen in all my time owning the car. The DIC working..... I took it to a guy at work and he was able to solder the broken ground. I put the dash back together and went through the troubleshooting guide again and everything tested fine. Started the car and went on a 2 hr drive and not once did it act up! !!

I still can't wrap my head around how/why that works but hey, I have my vette driving again! Thanks for all the tips and suggestions!

desertmike1

you have it working that's all that matters!