4th blown alternator


FBA

GT Owner
Dec 5, 2010
1,654
31.022340° N / 44.846191° W
My alternator blew for the 4th time in 2 months, last 2 times in the dyno during a pull.

We've changed it and even done a rebuild 2x. 1st time we changed it we noticed the bearings were shot, which was on the OEM alternator I got last year, but the last 3 didn't have that issue. There are no loads or spikes that we were able to measure.

I'm stumped...
 

tmcphail

GT Owner/Vendor
Mark IV Lifetime
Apr 24, 2006
3,996
St Augustine, Florida
Booooooo
 

nota4re

GT Owner
Mark IV Lifetime
Le Mans 2010 Supporter
Feb 15, 2006
3,584
I'm guess you are experiencing a high current short and you're blowing out the diodes. Two obvious places to look/inspect with my bet being on the second one. First, make sure battery is buttoned down as it should be and then with your hand, trace the positive battery cable as far as you can and make sure it is not compromised anywhere. Second, ideally with the rear pan removed, have a look at where the (+) battery cable attaches to the starter. Often, this connection will melt with the exhaust too close. Once again, make sure no compromises to the cable and/or connector. Any chance that the exhaust can torque into the exhaust? Exhaust components tight around there. Motor mount tight?
 

soroush

Ford Gt Owner
Mark II Lifetime
Aug 8, 2007
5,093
that is an odd one... has anyone else ever experience this? my car lived on the dyno for while and I never had any issues with alternator

has anyone done any "wiring" on your car? do you have boost a pumps or any other additions?
 

FBA

GT Owner
Dec 5, 2010
1,654
31.022340° N / 44.846191° W
I have a Boost A Pump
 

FBA

GT Owner
Dec 5, 2010
1,654
31.022340° N / 44.846191° W
No kidding - and it was going well too...
 

soroush

Ford Gt Owner
Mark II Lifetime
Aug 8, 2007
5,093
I have a Boost A Pump
are you running a bigger crank pulley too?
 

PeteK

GT Owner
Apr 18, 2014
1,204
Great Falls, VA
Bearings wearing out is odd. Possible one with a bad bearing. You said the other 3 didn't have bearing problems. What do you mean by "blew" and what did you do in the rebuilds? I don't see the connection between the dyno runs and the alternator failures. Need to know more about the failure mode.

One other thought: I haven't check the manuals on this yet, but is there some kind of cooling air duct to the alternator that is blocked?
 
Last edited:

Xcentric

GT Owner
Mark II Lifetime
Jul 9, 2012
5,204
Myakka City, Florida
What does "blew" mean? How do you know the alternators are bad? Do you bench test them?

Are you replacing with Ford parts or third world? What are you rebuilding?

Can't help with no information to go on.
 

Sinovac

GT Owner
Mark II Lifetime
Jul 18, 2006
5,551
Largo, Florida
are you running a bigger crank pulley too?
This was an issue on some of the GT500s with the bigger overdrive crank pulleys. They were spinning the alternator too fast.
 

B.M.F.

GT Owner
Mark II Lifetime
Jan 29, 2009
1,280
Minnesota
This was an issue on some of the GT500s with the bigger overdrive crank pulleys. They were spinning the alternator too fast.
The alternator is not spun off the 10 rib for the supercharger on either the gt500 or ford gt. So i have to dissagree there. Also i spin my engine 8300rpms with stock alt and an innovators west balancer which maintains oem 6 rib for acc belt on my ford gt.. 20000 miles like that.
 

nota4re

GT Owner
Mark IV Lifetime
Le Mans 2010 Supporter
Feb 15, 2006
3,584
last 2 times in the dyno during a pull
I still say a high current short. How is car strapped down to dyno? I'd be REAL suspicious of the (+) cable on the starter - maybe a dyno tie-down hitting it or compressing the suspension with strapping tight, etc. Another area to have alook at is the connections at the alternator itself. Battery, starter, and alternator is really the only 3 "exposed" areas for high-current, always hot, terminals.
 
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FBA

GT Owner
Dec 5, 2010
1,654
31.022340° N / 44.846191° W
No it's not a Dyno tiedown, because it has happened in the street on a WOT pull (often in this car ;))...I am going to check the cable near the exhaust...that makes a lot of sense to me too! I'm with the high current short philosophy too...

Guess I'm driving the Performante for a few days till this gets sorted out...lol
 

FBA

GT Owner
Dec 5, 2010
1,654
31.022340° N / 44.846191° W
What does "blew" mean? How do you know the alternators are bad? Do you bench test them?

Are you replacing with Ford parts or third world? What are you rebuilding?

Can't help with no information to go on.
I bought a new OEM from Ford last year as I was seeing a bit of flicker at idle. That one died on me in spring after only a few hundred miles on it, and the bearings were toast...so we didn't think the problem was anything beyond that...but we were wrong.

I took it to my shop, who said he felt he'd rather rewind and repair than replace. OEM wasn't expensive, but he replaced with heavier duty bearings and a higher current capability. Today, I asked them to see exactly what blew in the last 2 repairs and they are checking to see...

Didn't bench them...all we get when it happens, is 9 volts out of it...and no real current capability. Last night, the car just stopped running when I tried to take her home.

The rebuilder isn't a 3rd world rebuilder...he's actually pretty good with a good reputation, and my repair shop is Lamborghini Montreal, who does pretty good work and they don't tolerate shoddy sub's...

So, in the end, it is a Ford OEM that has been rebuilt now for the 3rd time...

Don't have more info than that, yet
 

Xcentric

GT Owner
Mark II Lifetime
Jul 9, 2012
5,204
Myakka City, Florida
Do you have headers? Headers will melt the wiring at the starter solenoid. See post #1 in this thread.
 

soroush

Ford Gt Owner
Mark II Lifetime
Aug 8, 2007
5,093
The alternator is not spun off the 10 rib for the supercharger on either the gt500 or ford gt. So i have to dissagree there. Also i spin my engine 8300rpms with stock alt and an innovators west balancer which maintains oem 6 rib for acc belt on my ford gt.. 20000 miles like that.
I suspect the rebuilt units are just not up to par... since almost no one else has had any issues with their alternator, I also ran the innovators west crank pulley on my car and spun to 8000 with no issues...

on the melted wire to the starter I had that issue as well all that happens is the plastic connector melts but the connection will remain if there was an issue with that connection you wouldnt be able to start the car in the first place.
 

Sinovac

GT Owner
Mark II Lifetime
Jul 18, 2006
5,551
Largo, Florida
The alternator is not spun off the 10 rib for the supercharger on either the gt500 or ford gt. So i have to dissagree there. Also i spin my engine 8300rpms with stock alt and an innovators west balancer which maintains oem 6 rib for acc belt on my ford gt.. 20000 miles like that.
Is it the a/c compressor that’s on the 10 rib belt?
 

nota4re

GT Owner
Mark IV Lifetime
Le Mans 2010 Supporter
Feb 15, 2006
3,584
The 10-rib drives the SC and the power steering pump. 6-rib accessory belt drives the alternator, AC compressor, and water pump.
 

2112

Blue/white 06'
Mark II Lifetime
Alternator failure is pretty common over the entire '07-'14 GT500 run.

Repeat alternator failure is also very common in F-series trucks (particularly with the Powerstroke) from the early 2000's until not sure when.

I have had to replace several. I asked the last time this subject came up here; does the GT use the same alternator? I am still on the original in my FGT.

I gave up and went with one of these units;



I am pretty sure the will build the alternator to fit your application.
 

FBA

GT Owner
Dec 5, 2010
1,654
31.022340° N / 44.846191° W
It's for sure not a load issue here...it's a dead short at high RPM, so no matter how much power we rebuild / rewind to, it won't fix the issue. I am looking in the exhaust area to see about melted cables as I believe that's where the issue is.