I keep thinking I've got this problem fixed and it keeps coming back.

If I ground the little red seed wire at the firewall the light does not come on. So this should eliminate the engine harness and alternator.

Its not the bulb because it works sometimes.

So I am wondering where the power feed comes from for the light. From the diagrams I have, it does not go through the fuse box on a 93. The oil pressure light is working and I think is on the same power feed. Is this correct? If it is it should mean the ignition switch is ok right?

Any ideas?

I recently had a similar intermittant problem where the brake, brake failure and amp lights would not come on when I turned the key. Eventually they would not come on at all. I also noticed that the dash lights would be dimmer on occasion, then return to normal brightness. One morning the car died with a dead battery. The problem was the small red wire on the alternator had come loose, the off completly. I tightened the connector and put it back, and all has been fine since.

absolute A#1 thing I would start with...

Put a volt meter to the battery with car off. SHould be about 12.5v. Then start the car... should be 13.3-14v. Maybe you already checked that...

You can go a long time with no charge to the battery if you mostly drive during the day...

--
-Matt I ♥ my ♂

Thanks, I have a dash voltmeter so I know when the alternator is not charging. Plus the ABS light comes on when only on battery for some reason.

Today it seems to be working. There must be a poor connection in the dash somewhere. It's not the alternator because I can get it charging by jumping the seed wire to the battery

Hello There,

This almost has to be a tarnished contact based on what you have posted.

Here is what I would check and clean (now this is based on the wire colors from an 86 and the notes from my broken Alt ground wire issue from a while back). Disclaimer Wire Colors may vary based on year and model.

Turn the Key to Post II and see if all the lights come on. That would indicate that you have a good circuit most of the time.

Check the following, you will most likely want to pull the instrument cluster unless you are young and flexible.

1. Check the contacts on the back side of the instrument cluster.

Change the Alt Bulb with another one and check the contact surface where the little connector makes contact. It may just be the contact on the back of the bulb or the bulb itself. The little bayonet contacts could be loose or just tarnished a bit.

Check the Blue/Red Wire Contact coming from fuse 13 (at least that is the color on my 86) Pin A on the Half Moon Connector. Shine anything else that looks dull or tarnished while you are in there.

Check the contact 11 (Red Wire going to the Alt) on the round connector on the back of the instrument cluster. Clean up the others while you are there.

Check the mating pins on both where the connectors plug in for tarnish, shine as needed.

2. Check the contacts on both sides of Fuse 13, shine with the Pink Pearl as needed.

3. Check the large gray connector on the firewall. Take a Pink Pearl eraser and give the male pin a good shinning up on the large connector. Check the inside of the female side and make sure it is also making good contact.

4. This is going to be a long shot but been burned by it once so here goes. Check the over all condition of the ground wire from the alt to the engine block. If in doubt replace it.

Thanks all I got and good luck,

Paul

Thanks I am going to pull out the cluster this weekend and check the stuff you mentioned. Its not the ground. I just had the alternator off to replace the wiring harness (the big wire shorted and burned the whole wire harness) and the ground wire is perfect.

"If I ground the little red seed wire at the firewall the light does not come on. So this should eliminate the engine harness and alternator".

Probably so....but it doesn't eliminate the connector.
Do you have battery voltage (12V) on the red wire at the connector, on the side that goes to the alternator?

"Its not the bulb because it works sometimes".

Could be the bulb socket, or a loose connection.
The (excitation) voltage for the alternator travels through the bulb to reach the alternator.
If the bulb blows, or loses continuity through it or it's circuit, the alternator won't charge.
The charge light also won't illuminate.

"So I am wondering where the power feed comes from for the light. From the diagrams I have, it does not go through the fuse box on a 93. The oil pressure light is working and I think is on the same power feed. Is this correct? If it is it should mean the ignition switch is ok right"?

The power feed (voltage) comes (un-fused) from the ignition switch to the instrument cluster, travels through the charge light, then thru the big connector at the firewall and directly to the alternator.
You should have 12V on the small (red) alternator wire when the switch is on.
Have you checked this?
Try grounding the wire at the alternator, and see if the charge light illuminates.
I know that you grounded it at the firewall, but check it at the alternator.
Is your engine ground strap to the chassis intact...loose?

The oil pressure circuit is fed from the same power source in the instrument cluster, so your problem is apparently from the cluster to the big connector at the firewall.

Just a few ideas
Hope this helps
steve

Thank you, yes that helps. I mainly wanted to know if I could eliminate the ignition switch. So that leaves the red wire or the instrument cluster as possible culprits.

93 240s don't have a connector at the firewall. The harness goes right into the dash. I have the wire spliced at the firewall, because of a burned alternator wiring harness.