Hey guys, here is a problem I have and very little time to solve it. I have an 84 vette that had a bad alternator. I charged the battery up and started the car and watched the voltage on the digi dash slowly go down and down and down.

I replaced the alternator but the battery was so bad even after charging it two more times, it wouldn't start. So I replaced the battery. I also replaced the connector to the alternator that goes to the spades. After I dropped in the new battery the car started right up. However even then I noticed that at the battery it wouldn't read past 12.5v and the digi dash read 12.2v. The voltage wouldn't drop but it wouldn't go up to the normal 13.5v either. The car held at that many volts.

Here is the bad part. After a few minutes I started noticing smoke coming out from under the dash. It didn't do this before. So I turned the car off and the smoke stopped. I waited a few minutes and started it back up and same scenario as above. I have taken apart most of the dash and I found a brown/white wire that runs from what appears to be one end of the firewall to the other. I cant really see if it runs into the fuse panel. I started removing some of the electrical tape that holds all these wires together and there would be less smoke but still smoke. Now, I turned the car on but not the engine. I could feel the wire get warm but not boiling hot like while the engine is running. With the car off the wire is normal. I cant find any damage to the wire and haven't found any short.

I took a look at the alternator and the plug that goes into the spades is not hot or melted and neither of the two splices are melted or damaged either. Can an alternator really cause this? Please help!!!!!!!!!

 

Does it look like a factory wire? The only thing under the dash that I see would be attached to the check engine light and Lamp driver module. Have you tried disconnecting to see if the voltage rises or even stops something from working? I repaired a lamp module awhile back for someone on here. If that what it turns out to be he can let you know where ordered the parts. It was a cheap fix.

 

OP - Do you have a FSM? There is a brown/white "resistance wire" in the charging circuit for the '84. The wire is 10 OHM I believe and for diagnostics I believe if the connector and the charge wire are good at the battery and also the alternator I'd remove the alternator and return it for a check on the bench. I'd maybe check the voltage with a DMM at both of the fusible links, I wouldn't rely on the Volt Meter in the cluster.

Are you sure you've wired the connector at the alternator correctly? I overlooked you mentioning the replacement of.

The "resistance wire" is in the RUN aspect of the ignition switch.

 

Yes it does look factory. Where and what do I disconnect?

 

Unfortunately I dont have an FSM yet. This is the same diagram I was following. I've had very little time to do anything more than I've done so I need a little extra help.

The alternator connector is wired properly except factory it's a red and brown wire versus the replacement which is a red and white wire. Where exactly is the fusible link? Not trying to sound totally stupid just pressed for time with everything else the world is throwing on me right now and basically finding time in between to take care of this. I gotta get it fix ASAP because of my stupid HOA.

Also, I never returned the core alternator. I was actually gonna put the old one back in to see if it was still happening. With the old "bad" one it didn't.

 

I'd maybe get the old alternator checked as well as maybe the NEW also - when a person creates a "new" issue replacing parts it's generally assumed you check your work before assuming anything else. Your situation I'd say makes it very clear that you need to check your work.

As you can see in the diagram you already mentioned having both fusible links are at the starter solenoid BUT you can check both wires without having access to the starter solenoid.

 

I think we got this. It's gotta be a bad alternator. Just for the hell of it I unplugged the brown wire from the alternator connector and started up the car.

Guess what? No smoke after ten minutes. Also the brown/white wire is cool to the touch. So I reconnected it and guess what? Smoke after a few minutes and the brown/white wire is hot as hell. I turned the car off and let it cool. I checked the batter with a VM and battery is good. I started it back up and checked voltage at all terminals. Voltage at the battery was 12.4V.....yeah I know sucks. Voltage at the BAT was 12.4V. Voltage on the red side of the connector was also 12.4V. Voltage at the brown side of the connector get this.......40.6V!!!!

We got smoke fellas. I turned it off and let it cool. After letting it cool I put the old alternator back in and connected it with all wires. The old alternator started cranking out 12.16V......even suckier! However, it was 12.16V throughout all connections and during ten minutes of running, no smoke and the brown/white wire is cool to the touch. I think we found the problem. Although I have never heard of this happening but hey it's a "rebuilt" alternator right?! Good thing I never took back the core.

One other thing that happened now and maybe it's nothing but I put the digi dash on and it's not lighting up. I looked at it with a flashlight and you can see the digits and see the RPMs go up when you step on the gas but I'm assuming it's because the older alternator is weak and is not putting out under 12V....around 11.7V. Am I assuming correct with the digi dash?

 

No lamp driver module on an '84.

 

My Haynes manual isn't all that great I guess, it covers all the years of the C4 and didn't specify that. I guess the FSM would probably be the one to go by.
I may have to go ahead and buy one.

 

I think we need to go back to some electrical basics.

Voltage+amperage=HEAT. You have heat which means you have these in adbunance. Since we are dealing with a 12V system we can assume we have about 12V more or less. For amperage to go up (what you have) resistance MUST go down.

Either the wire or something it is connected to has less resistance than it is SUPPOSED to have and causing more amperage to flow and thus smoke and heat.

If you have smoke, SOMETHING is damaged somewhere. You NEED to find it. Not optional at all unless you like more smoke.

Given the simple circuit, you could have a short to ground ANYWHERE on the brown wire or the orange wire.

The alternator could be the short. However, since you did both. IDK? That being said unless you have steady battery voltage at Pin 1 brown wire at the alternator it will NEVER charge regardless of if the alternator is good or not.

I would disconnect the alternator and go to Key on and see if you have battery voltage at the brown wire at the alternator. SHOULD be close to battery voltage within a tenth of a volt or so!!!

Its possible you have MORE than one issue. The original alternator could have gone bad and the new one maybe defective. You should NEVER have more than about 15V from an alternator unless the rectifier diodes took a crap. Switch to AC on your meter and take readings and see if any is present.

 

Alternator friends! I took the new one back to Autozone and it turned their bench tester off the voltage spiked so high.

The parts manager even said it was a good thing I didn't drive it. Luckily another store down the street had another one and the parts manager from the store I went to told me to make sure they test the new one before leaving the store cause he'd never seen that before. So I went to the new store and made them test now the new/new one and left them the old/new one.

I still have the old/old one in my possession so until I drop in the new/new one I'll let you guys know what happens.

 

Another reason I NEVER buy aftermarket alternators or starters. They are JUNK. I go OEM Reman (they do exist but cost more) or have it rebuilt by a good automotive electrical shop. Not worth the hassle.

Hope the new one works out for you. I would still check that wire VERY closely. You don't want to have other issues down the road.

 

Nope! There is definitely a problem elsewhere except this time it came from the alternator itself. The new/new alternator burned up. I could see the slight flame inside the case. Luckily the hood was up and I caught it immediately and shut the car off immediate.

I'm starting to really wonder wtf?! Could it really be as simple as the hiring harness/connector to the alternator. My neighbor has a friend who worked on nothing but Chevy's for twenty years and he said over the phone it sounds like the problem is somewhere between the battery to the starter or the starter to the alternator. Hell if I know at this point.

 

Hey guys, it did find one thing that is disturbing. Not sure if this can and does affect anything but maybe you guys can chime in.

After I took a break and came back to the car, I noticed that the bracket for the alternator below where it faces the front cracked....maybe from overtightening??? Not sure. But it's definitely cracked, maybe broken. Aren't all points of the bracket supposed to create a ground for the alternator? Could this be causing a short?

 

Yes, the case is grounded to the engine block as its ground. However, one cracked bracket should not cause this.

I'm in agreement with the neighbor friend.

Considering what has/is happening a through investigation of the wiring is needed.

 

If that wire is 10 ohms even if you put the whole 12-15 v across it would only draw 1 to 1.5 amps.

I cant believe that would heat t much esp not enough to make any smoke. Maybe someone replaced it with plain wire? Or the smoke came from the other alt?

 

It's almost like both alternators were doing the complete opposite. With the original alternator that wasn't charging we had no smoke just pretty much a dying alternator.

With alternator number two, we had a hot wire inside the car. With alternator number three we had a hot alternator. The best part is with no alternator in the car and just the key in the on position, my digi dash started working again. Let me ask this simple question. Should there be any voltage coming from the BAT cable with the car off? If so, what should it be? Or should it be 12+V with the car running? The battery is 12.44V with the car off. On the red wire of the alternator connector, it's also 12.44V. At the brown wire it's 0V. When I put it in the On position the brown wire also shows 12.44V.

I looked for voltage drops from the negative post to the alternator case, the ground, the engine block and I'm getting 0.00 or 0.01 max even with the key in the On position. I'm really starting to suspect that the problem is a bad crimp in the connector itself. I got up under the car today with a flashlight and looked all around the wiring and felt for any loose connections and just couldnt find any. When alternator three roasted it clearly roasted right at the spade where the brown wire connects.

 

Take the battery out completely, wait a while, unplug the alt connector, measure for voltage from the + battery cable to the alt connector that the brown/white wire goes to.

Once youre certain theres no residual voltage left (use lower and lower dc volt ranges) the you know its safe to use the ohm meter. Put the meter on ohms read from the + battery cable to the brown/white wire on the alt connector. Afterwards put your meter back on a high vdc range (best way to store it in case you take it out to use and forget its on ohms) .


Tell us the ohm reading.

 

I will definitely do that tomorrow. I have no alternator in the car right now and the battery is unplugged. Should I look for readings across all ohms setting or any one in particular?

 

The lowest ohms range most likely 200 ohms full scale