Electrical 4.6 96GT Buring alternators in a matter of 1 day of driving

96GTMike

New Member
Jan 5, 2021
2
0
1
26
Newport TN
I have a 1996 Mustang GT, 4.6L of course.
It is bone stock, aside from interior.
I have had issues with the car burning up alternators in just a couple of days at the most. this is the 3rd alternator in one month. I cannot figure out what is causing it, Ive checked fusible links and fuses, Wiring looks good. 0GA from alternator to Power block, 0 gauge grounds everywhere. I bought a bunch of 0ga black wires with lugs and just put them all over the place ( engine to chassis- battery to chassis) . It has a rotted trunk, not sure if there is wires back there to cause an issue ( i dont see wires back there)

The Battery gauge drops literally in a matter of seconds to right above the 8 miraculously able to start the engine and then the battery light is solid lit.

Yes we know the alternator is in fact bad now, but i am not wasting more money on a new alternator until I can diagnose the issue

I should note that the voltage from the D connector on the alternator with the engine running is : Green wire 11.93 volts Yellow Wire. 0.10 V white and black striped wire 0.00 v
 
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08GT500

Active Member
Jul 12, 2018
898
139
53
50
Massachusetts
I have a 1996 Mustang GT, 4.6L of course.
It is bone stock, aside from interior.
I have had issues with the car burning up alternators in just a couple of days at the most. this is the 3rd alternator in one month. I cannot figure out what is causing it, Ive checked fusible links and fuses, Wiring looks good. 0GA from alternator to Power block, 0 gauge grounds everywhere. I bought a bunch of 0ga black wires with lugs and just put them all over the place ( engine to chassis- battery to chassis) . It has a rotted trunk, not sure if there is wires back there to cause an issue ( i dont see wires back there)

The Battery gauge drops literally in a matter of seconds to right above the 8 miraculously able to start the engine and then the battery light is solid lit.

Yes we know the alternator is in fact bad now, but i am not wasting more money on a new alternator until I can diagnose the issue

I should note that the voltage from the D connector on the alternator with the engine running is : Green wire 11.93 volts Yellow Wire. 0.10 V white and black striped wire 0.00 v
Hi,
Sorry to hear, agree, 1 replacement failure-ok- beyond that, unlikely the alternators.. Battery flatten out quickly on its own connected/disconnected?
Clues suggest a larger circuit short, alternator loop, less protected by fuses.
1) Terminals disconnected, what’s the resistance between the terminals?
2) Have the battery load tested (parts stores do it for free). If terminals read as low resistance, may get lucky quickly by pulling fuses, yet sounds as if it may be less protected, larger circuit wiring.
With diagrams* in hand, log everything you’ve tested, ruled out. I can post them*(?)
3) Using a VOM, check the wires resistance to ground/each other in the alternators circuit first. Check for good contacts & verify no posts are physically striking ground slightly, follow along to ensure all wire insulation integrity.
4) Then, begin measuring resistance to ground on the larger wiring feeding the blocks & the starter itself (known water leaks?..look for moisture) , diagrams in hand, work outward from the terminals to the fuse blocks, after you’ve done a good visual..
5) Have a stereo Amp in trunk? Disconnect..
Then, begin pulling fuses to isolate them to see if resistance level improves between battery terminals.
6) Backtrack, any changes noted/work done, I.e: Mods, new parts, work done, or unusual running conditions, etc. around the 1st Alternator failure?
Will follow up once I see your response.
Good luck!
Best, John

Initial thoughts..
Battery, Alternator circuit, mains to fuse block wiring; moisture, Starter moisture; wire(s) melted to exhaust, chafed insulation from larger wiring to block, belt tension low; misaligned. Alt. O/P -2V (13.7-13.9).
 
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96GTMike

New Member
Jan 5, 2021
2
0
1
26
Newport TN
Hi,
Sorry to hear, agree, 1 replacement failure-ok- beyond that, unlikely the alternators.. Battery flatten out quickly on its own connected/disconnected?
Clues suggest a larger circuit short, alternator loop, less protected by fuses.
1) Terminals disconnected, what’s the resistance between the terminals?
2) Have the battery load tested (parts stores do it for free). If terminals read as low resistance, may get lucky quickly by pulling fuses, yet sounds as if it may be less protected, larger circuit wiring.
With diagrams* in hand, log everything you’ve tested, ruled out. I can post them*(?)
3) Using a VOM, check the wires resistance to ground/each other in the alternators circuit first. Check for good contacts & verify no posts are physically striking ground slightly, follow along to ensure all wire insulation integrity.
4) Then, begin measuring resistance to ground on the larger wiring feeding the blocks & the starter itself (known water leaks?..look for moisture) , diagrams in hand, work outward from the terminals to the fuse blocks, after you’ve done a good visual..
5) Have a stereo Amp in trunk? Disconnect..
Then, begin pulling fuses to isolate them to see if resistance level improves between battery terminals.
6) Backtrack, any changes noted/work done, I.e: Mods, new parts, work done, or unusual running conditions, etc. around the 1st Alternator failure?
Will follow up once I see your response.
Good luck!
Best, John

Initial thoughts..
Battery, Alternator circuit, mains to fuse block wiring; moisture, Starter moisture; wire(s) melted to exhaust, chafed insulation from larger wiring to block, belt tension low; misaligned. Alt. O/P -2V (13.7-13.9).
nope car is absolutely bone stock. factory stereo, It is a GTS model. no back speakers etc. the single wire on the alternator appears to have become bare small wire coming from d connector to single pin on top back of alternator. Could that have cause it? battery isnt great. I put it on my load tester. I have some tools ive stocked up on. resting voltage for the battery is 11.43 volts. Vehicle off parasitic draw of 0.06 V.
 

08GT500

Active Member
Jul 12, 2018
898
139
53
50
Massachusetts
Hi,
Battery resting voltage should be no lower than 12VDC, that alone is a fail if it’s been adequately charged externally at rest.(?)
Surprised zener diodes in EEC are even conducting below 12VDC & starting the car.
Parasitic loss test in series connection between battery & terminal @ 6/10th’s of 1 DCV isn’t alarming.
-John
Edit: Try charging you're battery with a good charger on a 10A setting for 6-8 he’s to see if it will level up to/ better 12.2-12.6 V, check that it’s not getting hot during so, if this fails, I’d replace the Battery.
Chart, C/O LMR..
 

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08GT500

Active Member
Jul 12, 2018
898
139
53
50
Massachusetts
nope car is absolutely bone stock. factory stereo, It is a GTS model. no back speakers etc. the single wire on the alternator appears to have become bare small wire coming from d connector to single pin on top back of alternator. Could that have cause it? battery isnt great. I put it on my load tester. I have some tools ive stocked up on. resting voltage for the battery is 11.43 volts. Vehicle off parasitic draw of 0.06 V.
Hi,
When tackling a charging system issue, a questionable battery is handicapping you from the onset. Bare conductor is melting due to excessive draw overheat(?)
I’m guessing you went with an OE stock (not a 130A) O/P Alternator, stock wire is near/at its current carrying limits in stock form, upgrade the terminal with a fused AWG #4 conductor for the Alt. circuit with a screw-type lug or equivalent as it needs replacement anyway. That alone can be a problem- yes.
Best!
John
 
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dr.zed

Member
May 17, 2020
17
6
13
71
Nova Scotia
... a 12V battery will not likely start. "Good" batteries will be about 12.5V when the car is off.
A dead or dying battery can take out an alternator quickly, though one day is fast.
Have you replaced your battery?