Looking for some help electrical PLEASE

[RacqFan1]

I have a 99 cobra, the alternator was still original 71k miles. it stopped charging correctly i was down at 10.8 volts and the alternator smelled like it was cooking some material, I changed it with a Bosch rebuilt unit 130amp stock replacement, everything was fine during 1 hour test drive yesterday NO ISSUES. Today i had to take it out for a small cross town drive 3/4 mile and between 2-3 gear i heard an exhaust backfire, all electrical instantly was dead, everything, gauges swept right and stuck there.no lights, nothing like it had no battery, as I was walking home, I decided to go back to car 10 minutes later, the electrical was back on, I fired it up, it was running bad, got it home and electrical 100% out again in my driveway, i walked in house came out 10 minutes later and still nothing, put meter across battery and showed 12.79Volts, so i decide to disconnect battery, hook it back up and all electrical is present again, I started it for 5 min and shut it off. before the alternator going bad this car has had zero issues, not a blink of a problem. In my mind i think the only thing i touched was the alternator so i want to know if this can possibly be the issue, before i installed this bosch rebuilt i never had these symtoms or any electrical of any kind, all cables are tight and in proper order, why would it suddenly lose 100% electrical power, then later come back?

Thank You

 

[OldSVTGuy]

Just a suggestion from a previous experience with blown alternators. Check your primary and secondary wiring to see if you are shorting out anywhere. I worked on a car that blew two alternators in one day; it turned out to be a battery cable shorting against the frame rail. The insulation on older wiring does tend to get brittle. Just a thought.

 

[RacqFan1]

Just a suggestion from a previous experience with blown alternators. Check your primary and secondary wiring to see if you are shorting out anywhere. I worked on a car that blew two alternators in one day; it turned out to be a battery cable shorting against the frame rail. The insulation on older wiring does tend to get brittle. Just a thought.

I will give it all a good look over, the alternator itself can't internally short can it? causing this issue, I have never seen anything like it but i will follow your recommendations

much appreciated OldSVTGuy


thank you

 

[RX1Cobra]

Sounds like a ground to me. I think the 99's had a problem with the ground strap to the engine. Take a look there. Could be your alternator was never the problem.

 

[CammyTheCobra]

I have a 99 cobra, the alternator was still original 71k miles. it stopped charging correctly i was down at 10.8 volts and the alternator smelled like it was cooking some material, I changed it with a Bosch rebuilt unit 130amp stock replacement, everything was fine during 1 hour test drive yesterday NO ISSUES. Today i had to take it out for a small cross town drive 3/4 mile and between 2-3 gear i heard an exhaust backfire, all electrical instantly was dead, everything, gauges swept right and stuck there.no lights, nothing like it had no battery, as I was walking home, I decided to go back to car 10 minutes later, the electrical was back on, I fired it up, it was running bad, got it home and electrical 100% out again in my driveway, i walked in house came out 10 minutes later and still nothing, put meter across battery and showed 12.79Volts, so i decide to disconnect battery, hook it back up and all electrical is present again, I started it for 5 min and shut it off. before the alternator going bad this car has had zero issues, not a blink of a problem. In my mind i think the only thing i touched was the alternator so i want to know if this can possibly be the issue, before i installed this bosch rebuilt i never had these symtoms or any electrical of any kind, all cables are tight and in proper order, why would it suddenly lose 100% electrical power, then later come back?

Thank You

Check the ground harness, as mentioned above. If you conclude it's all set, than there's something else I want you to check. Alternators have what's called a voltage regulator, and it is exactly as it sounds. Sometimes they can fail, causing a surge of extra power to run through the cars systems. You can fry computers this way. What you should be checking is the battery terminals with the car running, not off. Check the voltage there, healthy or sustainable voltage output will be ~13.5v - ~14.5v. Check it idling and revving it up. You're more specifically looking to check at revving voltage. If the regulator is toast, as you spin your motor the higher it revs the more voltage will be produced and won't be regulated if the regulator on the alternator is toast. They cab produce an excess of 15v and I've actually seen as high as 19v and who knows could go higher. But if that happens, it will cut out the entire vehicles electrical system, until the voltage output goes back to nominal levels. Make sure the output voltage is stable on high revs and idle. Check the ground and your alternator output idling and revving before you further continue.

Yes, they can internally short. Your description if I understand it correctly, I'm leaning towards your alternator voltage regulator. Check that, in the way I explained above.

 

[RacqFan1]

I thank you, I will check all of the above mentioned replies, I am grateful to receive input from all of you,again Thank You, I only had a half hour in the garage today due to family matters, but I did notice that the power distribution box side cover looked melted a bit in the corner, this stems from when my Viper alarm was installed, the stud that the hot wire from ALT/BAT gets attached to was rattling around and loose, the alarm was tapped in there with its own wire on a spade lug terminal, everything was loose and flopping around, the nut was not even bottomed on the terminal, i corrected that issue and will check the alternator tomorrow for Voltage output readings under high revs to see if the regulator keeps it in check, I will also check all grounds and wires through out, i figured if i lost power due to bad connection even for a split second it would act like i turned the key off while it was running and i did infact lose ALL POWER ELECTRICALLY., i only drive the car maybe 1000 miles per year if that, so this been in this condition for some time, i asume that when i changed my BAD alternator on Sunday, I must have upset how the terminals were resting on eachother and problem raised its head.

 

[OldSVTGuy]

Sounds like you may have found it. Good catch. I think I've read of others that have had problems with the distribution box.