Intermittent 3 light charging problem

[eltrain]

Hey folks,

Long time lurker/consumer here.

Have a 1990 3VZE w/AT that has the 3 light (BRAKE, Charge, A/T TEMP) problem, but intermittently. New battery, new alternator, redid all the grounds I can find. Still don't know just where the one in the passenger kick panel is, is it in the mount of the ECU itself? Been through the threads on here I could find regarding the problem. The load on the engine seems to affect the lights coming on, if you turn the blower and headlights on it will go on/off. the engine rpm goes up when the lights go off, and vice versa. Checked the connection from the ALT to the BATT, it's good. 80A fuse by the battery is good, as are the connections. It's the intermittent nature of the problem that is bugging me, if it would just do one or the other it would be much easier to figure out. Thanks for reading (and hopefully shedding some light!).

John

 

[flyinhawaiian01]

are you using the same stock +12v wire from the alternator to the battery? I'm thinking your wire is corroded or has a really high resistance, which can cause the charging system to not actually get enough current to the battery. You can upgrade the wire to an 8awg or larger wire pretty easily (at least on the 4 cylinders it is).

The batt/brake lights on the dash generally tell you that the alternator is failing, but since you've replaced the alternator already (assuming it is a good or new/rebuilt unit), and you've replaced the majority of ground wires, the only thing I can think of is that +12v wire. I know you checked it, but if its gotten a lot of acid into the cable from near the battery, and it has seen a lot of moisture, that will deteriorate the copper over the years. It will still make a connection, but its now working more as a resistor than a wire.

Other than that, maybe try doing the "BIG 3" to bypass whatever's causing the issue. Not sure if you know about it, but Google that term to find out what its all about. Sounds like you've already done some of it with the ground wires, no sense stopping now! :bigok:

 

[eltrain]

Thanks for the reply.

Yeah still the stock wire from alt to batt. Measuring 0 ohms and 0V while running across it, but I'll rerun it anyway. Batt to ground is fresh, and so are both engine block grounds. One up by intake mani/cowl and one drivers side head/fender. Redid and soldered the crimp on the fusible link between fuse block and battery. Did notice there seems to be lower voltage coming into the alternator via the smaller wires, from the diagram they go through the ignition switch and other mazes. It's a game of assumptions, and weeding them out it seems. The rebuilt alternator never stops worrying me either.

are you using the same stock +12v wire from the alternator to the battery? I'm thinking your wire is corroded or has a really high resistance, which can cause the charging system to not actually get enough current to the battery. You can upgrade the wire to an 8awg or larger wire pretty easily (at least on the 4 cylinders it is).

The batt/brake lights on the dash generally tell you that the alternator is failing, but since you've replaced the alternator already (assuming it is a good or new/rebuilt unit), and you've replaced the majority of ground wires, the only thing I can think of is that +12v wire. I know you checked it, but if its gotten a lot of acid into the cable from near the battery, and it has seen a lot of moisture, that will deteriorate the copper over the years. It will still make a connection, but its now working more as a resistor than a wire.

Other than that, maybe try doing the "BIG 3" to bypass whatever's causing the issue. Not sure if you know about it, but Google that term to find out what its all about. Sounds like you've already done some of it with the ground wires, no sense stopping now! :bigok:

 

[flyinhawaiian01]

Yeah, that would be my other guess, the alternator may not be good,even though its been rebuilt.

I've seen a good amount of discussions on rebuilding alternators and having them not put out the proper current due to improper winding and/or oversized copper wiring (or decrease in the amount of wire, which is also how they get more current). If the rebuilder re-wound your alternator with a much larger copper wiring, it may not be able to produce enough current at lower rpms, and the larger the wire is, the higher the rpm needs to be to get the same amount of current (although as you increase rpms, the current will rise at a higher rate than a stock wound alternator).

I'd say to also have someone test the current of the alternator to see what it's actually putting out and at what rpm you're seeing solid, clean, stable current.

Or, just try a stock alternator that you know works, see if the problem goes away. Easy enough to borrow one from a buddy's truck for a day or so and see if it eliminates the lights.

 

[eltrain]

I think I can still exchange it, might take it in and have them just swap it. Makes sense; less windings, less voltage. Just like an electrical transformer. Heck, if it's a rebuild the brushes might even be sticking. Still gonna try the wire first, since I have all that lying around already.

Thanks again for the advice, I'll report back once I get a nicer day to work on it. And get the wasps out of the fenders, they will ruin a wrenching session quick.

 

[eltrain]

Seem to be right on the edges of success and failure. Sometimes when idling, the three lights will be off. Turning on the parking lights, the blower, or hitting the brake pedal will make them light. Anything that draws current. Then they will go off again when turned off. On a whim I took standard jumper cables and bridged the alternator+ to batt+, no change in condition. Going to exchange alternator next.

 

[eltrain]

Exchanged alternator for a different one and all seems to be good. Maybe it was wound incorrectly. Thanks for all the advice. Now onto the brakes.