Yes, I am a Moron - Electrical guys help!

[fjules]

Lets get the moron comments out of the way. I have my battery relocated in the trunk. I disconnected it to do some mods (new radiator & IC tank). Finished the install and reconnected the battery. The problem is I connected the battery backwards!!! I walked to the front of the car and there was smoke coming from the driver side fuse box area. I quickly disconnected the battery and inspected the area throughly. I could not find anything obviously burned. I reconnected the battery and the car starts no problem. What components should I check for damage? Since this is a DC system I would think the only things that could get damaged would be IC's and diodes. Please share your thoughts.

 

[Dana]

The alternator is probably toast.

 

[fjules]

Yeah, I am kinding of thinking that because I do not see any signs of melting of the wiring in the area of the smoke. The only other thing over there is the alternator. Alternators don't do well under revers bias? Any way to tell if it is dead or should I just replace it?

 

[1svtfan]

Yeah, I am kinding of thinking that because I do not see any signs of melting of the wiring in the area of the smoke. The only other thing over there is the alternator. Alternators don't do well under revers bias? Any way to tell if it is dead or should I just replace it?

With the car running is the voltage at the battery about 12 volts or closer to 14 volts? MIght be a quick way to check, but it may still be toast with a load. Turn the lights and ac on while its at idle and see what the voltage looks like.

 

[Oxford Snake]

Start the car and then disconnect the battery, if the car dies then the alternator is toast.

 

[fjules]

Well, so far, ran the car, aeroforce scan gauge indicates battery voltage = 13.6V. When I turn on lights and ac drops to 12.6V. Sound good or bad? Found first problem, radio will not turn on, anybody know which fuse that is?

Is it ok to pull the postive battery lead off with car running to see if car dies? Just a little gun shy, do not want to screw anything else up.

 

[oldmodman]

Check the fusable links for partial melting. They are a smaller guage wire spliced into one of the main feed wires coming out of either the plus battery cable or the main fuse box under the hood. They are designed to literally burn up if exposed to a dead short. The factories use them instead of a big fuse because they do not degrade when expose to a large current draw over a long period of time. If it has partially melted it will have to be cut out and a new one spliced in.

 

[Dana]

Don't disconnect the battery cable to check the alternator. This could damage the alternator. The current it is producing has no where to go.

Anyway, check that the voltage not too high either. A diode can either go open or short. If it shorts, the voltage can go way up. This can over charge a battery.

 

[Oxford Snake]

Don't disconnect the battery cable to check the alternator. This could damage the alternator. The current it is producing has no where to go.

My bad, that's what I had always been told.

 

[svtnos1011]

your flux capacitor is definately toast

 

[wjurls]

Don't disconnect the battery cable to check the alternator. This could damage the alternator. The current it is producing has no where to go.

Anyway, check that the voltage not too high either. A diode can either go open or short. If it shorts, the voltage can go way up. This can over charge a battery.

I don't usually like to get involved in electrical discussions due to lots of dissagreements and missinformation but I would like to clarify that an alternator only produces enough current to meet it's demand at the time. A 150 Amp alternator may only produce 20 amps of current if all that's on at the time is the engine and maybe the dash lights. Ever notice when you go to jump a dead car how the running cars alt start to howl when you connect the cable to the dead car? If they were always producing max current they would always howl and probably only last a few days.
On that note I still wouldn't use the "disconnect the cable" method on any computer controlled vehicle. For one it is a largely unreliable method and the main point is that battery acts as a real nice buffer for the electrical system to help surpress voltage spikes and sags. You take a chance of a nice electrical spike when you disconnect the cable on a running car (especially if you have a bad regulator and your voltage is too high). Your best bet is to remove the alternator and go get it load tested. Or you can take the car in and have the whole starting/ charging system tested.

 

[coild]

+1!!!!!

 

[Dana]

I don't usually like to get involved in electrical discussions due to lots of dissagreements and missinformation but I would like to clarify that an alternator only produces enough current to meet it's demand at the time. A 150 Amp alternator may only produce 20 amps of current if all that's on at the time is the engine and maybe the dash lights. Ever notice when you go to jump a dead car how the running cars alt start to howl when you connect the cable to the dead car? If they were always producing max current they would always howl and probably only last a few days.
On that note I still wouldn't use the "disconnect the cable" method on any computer controlled vehicle. For one it is a largely unreliable method and the main point is that battery acts as a real nice buffer for the electrical system to help surpress voltage spikes and sags. You take a chance of a nice electrical spike when you disconnect the cable on a running car (especially if you have a bad regulator and your voltage is too high). Your best bet is to remove the alternator and go get it load tested. Or you can take the car in and have the whole starting/ charging system tested.

The reason an alternator doesn't always produce full output is because it's output based on battery voltage. The lower the voltage, the higher the alternator output. As the battery voltage approaches 13.6 volts or so, the ouput of the alternator begins to decrease.
The reason the alternator may begin to howl when connected to a car with a dead battery is that the regulator is seeing the battery voltage of the dead battery now also. This in turn causes the alternator to produce much higher output.
The output is also based on the speed of the alternator.
The load doesn't enter into this anywhere, unless you consider the dead battery that is sensed by the regulator as a load.
The point is that an alternator will produce voltage and current under any conditions. With no battery in the circuit, the regulator can see zero volts, so it goes to maximum output. This may be brief, but it can be enough to do substantial damage to many things in the electrical system.

Dana

 

[wjurls]

We are kind of saying the same thing but not exactly. The Alt output current is regulated by ohms law and nothing else. The regulator doesn't "see" any outside voltage but simply regulates the output voltage of the alternator. If this voltage is 14.4 volts then the regulator will try to maintain this voltage providing the alternator has enough current to meet the demand. What increases the demand is actually the resistance of the electrical system. A dead battery has a very low resistance and therefore will strain a alternator. Conversly when the battery is fully charged it has a high resistance and therefore puts very little load on the charging system. As resistance decreases on a circuit with a fixed voltage current must increase to maintain the voltage. Remember Ohms law dictates that V=IxR where I=current in amps so when (R) (resistance) decreases (I) must increase to satisfy (V)

 

[CPViolation]

Maybe killed the bridge rectifier in the alt.

 

[RealBadDude]

Well, so far, ran the car, aeroforce scan gauge indicates battery voltage = 13.6V. When I turn on lights and ac drops to 12.6V. Sound good or bad? Found first problem, radio will not turn on, anybody know which fuse that is?

Is it ok to pull the postive battery lead off with car running to see if car dies? Just a little gun shy, do not want to screw anything else up.

12.6 seems a little low...

but i wouldnt go replacing parts unless you know their bad. if the car runs fine, no check engine light or any others, then i wouldnt worry about it until some problem surfaces...