Alternator Wire Getting HOT

[musicbum82]

Hi All,

My alternator died on my 93 Camry 5SFE and now I have a dead battery. I got a jump after installing the new alternator and everything seemed normal.

Then I noticed the smoke pouring from under the hood. The rubber cover to the generator wire caught fire and the end of the wire was glowing like a coil in a toaster. I took it off and managed to limp my car home under battery power.

Any ideas on the glowing generator wire? It's not the wires in the harness but the one that connects via a small nut on the top of the alternator.

Thanks,

Marc

[LynchburgCSI]

Generator? I think you mean alternator. In order for something to heat up like that, there has to be a TON of resistance. I'm guessing since the only thing different before you had problems is a problem with the alternator itself. I'll wait for someone more familiar with alternator specific problems to chime in though.

[musicbum82]

I was thinking along the same lines, that it was just a ton of resistance in the wire. How would I replace that wire? It runs into that plastic block that hangs between the timing belt cover and the valve cover. Is there a way to just bypass the old wire and put in a new one?

[SuLLiVaN88]

could it be a bad voltage regulator? if it was allowing too much power through could melt the rubber and get the wire hot... but then again it would probably fry your battery too, at least that is what happen to me

[95PimpingCamry]

The problem is that too much current is running through the wire. If there was too much resistance there wouldn't be enough current at 12 volts to burn off that much power required to make it glow.

You have a short from that wire to ground somewhere.

[LynchburgCSI]

Originally Posted by 95PimpingCamry

The problem is that too much current is running through the wire. If there was too much resistance there wouldn't be enough current at 12 volts to burn off that much power required to make it glow.

You have a short from that wire to ground somewhere.

uh. current is a direct factor of resistance. at 12 volts, a car can generate enough current to overwhelm the wire. overwhelming the wire because it's resistance is too high. toasters work on the same principle. high resistance + high current = heat. Enough technical junk though.

+1 on checking for a short.

[95PimpingCamry]

^ Lynch, yes I know how voltage, current, resistance (or impedance), and power are linked together. V=IR and P=VI. Just remember that as resistance increases, current will decrease. I just find it hard to believe that an alternator wire with too much resistance, and NO short, could glow red. I could very well be wrong, I just don't think that I am.

[2JZ-3VZ]

Was the entire wire hot, or just the point of connection? I would make sure its not grounding out on the body of the alternator around the battery post, especially if the eye terminal is bent downwards or something (i've seen it happen alot), Also make sure the battery post insulator is still there, if the alternator is reconditioned they may have left it out, or it may be cracked/broken (or if it was a new one, it still may be cracked/broken from overtightening the battery nut).

If the entire wire was hot, i'd check back along the wire, through the harness/etc and make sure there are no shorts.

if you can safely, i'd run the alternator (run the car) for a short time and see what voltages are being pushed out with a multimeter, check at the battery and the alternator, if theres no short, they should both be the same (though technically, if there was a decent enough short in the cable between the battery and alternator, the fuse on the battery side would have blown, thus protecting the battery, but not the alternator, but that'll also mean you'll have 12 volt reading at the battery and 14v+ reading at the alternator with a blown fuse in the loop)

Though if you have a multimeter, you can always disconnect the alternators battery lead at both ends, and check it for continuity from one end to the other, and also from one or both ends to ground/the cars body/engine block. If its a dead short, that'll tell you. And for good measure flick it to ohms and check it for an excessively high ohm reading

personally though im going to put my tips on there being a short somewhere between the battery post of the alternator and the alternator fuse near the battery (definitely check the fuse, cause if there was a short, it definitely would have short current from the battery side of the wire as well, ie the current from the alternator would travel down the wire to the short then short to ground, the other side of the short, the wire from the short to the battery, would not just be empty, it would have current traveling from the battery positive term in the opposite direction toward the same short, the difference is, the battery side is where the fuse is usually located)

and the current argumant, well, technically your right pimping, if there was a high resistance the current would drop assuming voltage and resistance stayed relatively the same. By Lynchburg's reasoning, the OP would have made his alternator charged at 100% the whole was home by removing the battery lead (which would change the resistance from what ever the lead was to infinite). Just doesn't work that way

[djb2]

Was the whole wire was burnt?

Did it cool down after shutting off the car, or only after disconnecting the battery?

Did the car run normally after disconnecting the alternator?

My guess is that the alternator had a bad diode pack. When a diode shorts out, the battery dumps its energy through the alternator. Most of the connections can handle a lot of current, with the alternator positive wire being the most likely to overheat. When you disconnected the battery, the wire cooled off enough to disconnect. Once disconnected, the battery was not longer being drained through the wire and the car ran normally, albeit under battery power only.

[musicbum82]

Wow guys, great answers! Thanks for all the suggestions!

The alternator has a good ground, the grounding wires from the body to the engine block ground out.

However, the wire that connects to the top of the alternator (the one that connects via the nut) showed a high level of resistance between the mounting end and the positive pole of the battery when I put the multimeter on Ohm mode.

Per 2JZ's instructions, I checked for continuity between the small post on the alternator and the metal housing of the alternator, there was none.

It seems like the wire is the problem.

Can I just bypass this wire and connect a new one from the connector to the positive pole of the battery? I assume that I would have to add a fusable link in this new wire.

Once again, Thanks! Toyotanation forums once again pull my ass out of the fire!!!

[musicbum82]

UPDATE: I pulled off the wiring loom cover and the wire looks fine, except for at the point of connection on the alternator side. When it was hot, it was glowing at the point of connection but the wire looks fine about 2-3 inches back. Between the wire at the point of connection to the alternator and the block, I'm getting about 500ohms of resistance.

[musicbum82]

FIXED! The alternator passed the initial tests, but at the urging of my neighbor I brought it to the car parts store to have it tested again. It passed once and failed twice, so they gave me another one on the spot.

I also cut the wires back to get a clean connection. I wanted to get a new connector, but I had to make due with the old one. The car runs great now!

Thank you all SO much!

[Mike Gerber]

Thanks for posting the solution.

Mike