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View Full Version : Alternator dead at 50k miles


ausie
01-22-2012, 01:46 PM
It finally went out.... Car had several months undriven last year which resulted in a dead battery. I had revived the original battery by charging it with jumper cables. All was well except when you punch the throttle hard. The higher RPM's resulted in the battery light comming on. Changes that I had made was to the programming of the CPU. Advanced timming and slight performance mods (such as higher red line). It is possible that the original alternator may have been overspun at 7000RPM. I will drop the redline back to the factory default when I replace the alternator. I am considering the PA performance alternator with a higher output current (170A) than the stock 130A alternator. I believe the advanced timming may have contributed to the battery issue as well as the high setting on the cut-off RPM. I had also replaced the battery recently but the alternator was not charging the battery. With the engine running, voltage on the battery would drop to 11.9V over the RPM range. Under idle conditions the battery voltage was measured at 13v. This was prior to the alternator going out. Now, all I get is the battery voltage and no indication of voltage increase from the alternator. More than likely the voltage regulator was not operating properly before the alternator began to fail. Everything is stock with the exception of the cat-back, tune, MAF, and CAI. I may have the O2 sensors replaced when I have the clutch installed. Better to have new sensors since they degrade over use.

ausie
01-30-2012, 07:28 AM
I ordered the 130Amp alternator (PA-2606) due to the better pricing. It was only $50 more than a remanufactured alternator of unknown origin ($10 less than the ford remanufactured alternator GLV-8616-RM).

I was hoping for an easy install, unfortunately I will have to take a coolant bath. Too bad I already flushed the cooling system before I moved down. No big deal, it is an easy task, just more work.

ausie
02-03-2012, 07:25 AM
I received the alternator two days ago. I went back to the web site to look up the pulley ratio calculations and discovered that the stock OEM pulley is too small for the PA alternator. Stock alternator pulley is 2.6" in diameter. I was uncertain about the actual size of the lower drive pulley 7.4", 7.5" 7.6"? In searching many forums, CobraBob Q&A was helpful (found resource on svtperformanc). Along with that, there were many treads on what alternator is good etc....

The trick is to know the minimum RPM and maximum RPM of the replacement alternator. The 6G family PA Performance alternator (2606) has a minimum RPM requirement at which it will generate a charging voltage and a maximum RPM requirement not to exceed or overload and failure will occur on the voltage regulator (and or bearings). The last thing I wanted to do is install a new alternator only to burn it out on the test drive.

PA alternator specs: min alternator shaft rpm: 1800, max alternator shaft rpm 16000.
Ford OEM alternator specs: minimu alternator shaft rpm 2400, max alternator shaft rpm (unknown).

The stock drive pulley is 7.625" (7 5/8)
The stock alt pulley is 2.6"

Pulley ratio is 2.93. If I used the factory installed alt pulley, the redline alternator shaft speed would be 19045. That would cause early failure. Unfortunately my tune will allow max RPM up to 7000RPM which would equate to 20510 shaft rpm on the alternator. The 2.6" pulley would make sense due to the higher minimum shaft rpm to generate charging voltage for the factory alternator. At least I am greatful that the alternator did not come with a pulley installed. What is needed for the PA alternator is a 3.2" pulley.

The pulley ratio with the stock lower drive pulley and the 3.2" pulley will be 2.38. (7.625/3.2=2.38) The alternator shaft speed would be 1949rmp at engine speed of 819rpm. At redline (6500 rpm) the alternator speed will be 15470 which is below the 16000 maximum for the alternator.

alternator shaft speed is the engine rpm x pulley ratio.

Always check the spec on the alternator and verify the pulley ratio is correct. It is desirable to keep the alternator shaft speed below the maximum RPM. In my case, I will have to drop the redline back to the factory setting. It just so happens that once I increase the redline (engine cutoff to 7000rpm is when I started having issues with the original alternator).

I do not mind waiting for the 3.2" pulley to arrive (metco). I would rather have done it right the first time, if it fails, it would be related to the alternator components and not due to overspinning.

I have read many posts about the alternator issues. There are those that claim they had failure while underdriving the alternator. Many of these people have larger drive pulleys installed to increase boost on the Eaton. More than likely they are only referencing pully ratio charts for the facctory installed alternator and not taking into account for the specifications on the replacement alternator.

Keep in mind, even the rebuilt alternators that are direct replacments may have different specs than the original installed alternator. I have looked at many on the internet that had different amp outputs and maximum alternator shaft rpm. There were some that did not publish the min/max speeds.

ausie
02-04-2012, 03:16 PM
I have seen many how-to-do-its on removal of the alternator.
They are all very good, but there were some items missing. It is a bit tricky getting access to all of the bolts but with patience it is not all that big of a deal.

The obvious:
1. Raise the front end and support with jack stands.
2. Remove the left front wheel ( ease of access, this is optional).
3. Disconnect and remove battery and battery tray.
4. Use a 1/2 in drive breaker bar to remove tension in the drive belt. The easy way to get the drive belt off the supercharger pulley is to slip the belt off the lower idler pulley below the supercharger. Now you can remove the belt from the alternator pulley.
5. Remove the electrical connections from the alternator (plug and power cable).
6. Loosten but do not remove the top long bolt on top of the alternator. If you take it out too soon, the alternator will be in the way of removing the alternator braket.
7. Remove the lower alternator bolt. Tight squees. I had to use a ratcheting combined with box end wrench to remove the bolt. All of the hoses will be in the way. Take your time.
8 Remove the two bolts that hold the alternator bracket in place. You do not have to remove the bracket that holds the flexible line.
9. Grab hold of the alternator pully while removing the upper bolt on the alternator. Carefully release the alternator.
10. From the underside of the car, the alternator will drop out between the coolant hose and the frame of the Cobra. If you forget to remove the alternator bracket you will not be able to remove the alternator.

I was able to get it out witout banging a knuckle or cursing at the engineer who designed the engine.
Just for curiosity, and to verify that the alternator was dead and not related to a wire or floating ground, I had the alternator tested. Sure enough it was dead. Now for the fun part. I decided to take it appart. The rear bearing is difficult to remove. At this point I did not care. Three bolts and the case can be pryed appart. I removed the voltage regulator that houses the brushes. Brushes looked fine, contact surface area on the rotor looked good too. Now I think I understand how the alternator operates and why there is a 20A fuse for the alternator in the power distribution box. The brushes are used to connect to the rotor winding. The plug connection is used to alter the magnetic field generated on the rotor to alter the output of the alternator stator coils. I could test the stator diodes to see if they are still good. I am curious to find out if it was a diode failure, I did see some cracks on the stator wire encapsulated circuit assembly. Perhaps the embedded metal connections were damaged or erroded. Besides that, the rotor did not move freely in the alternator assembly. It did rotate but did not sound healthy. I did however keep the alternator pulley. In order to remove it you will need an impact wrench and once you loosten the nut it will come off easily.

Now I am tempted to change the supercharger pulley. Too bad the 2.6" alternator pulley will not fit, but that would be too small anyway.

Snoopy 777
02-06-2012, 09:37 PM
I changed the alternator on my 2007 GT500 w/ a PA alternator, it was a total pain getting to the bolts. :(

ausie
02-07-2012, 12:01 AM
I think there is less working space in the GT500. I am sure things may be easier with the cooling system hoses removed, but at least it was not that bad removing the alternator without dumping the coolant.

Where is the alternator on the GT500? Is it in the same area?

I sure hope the PA alternator will not fail prematurely as others have found out.

I just got the 3.2" pulley today. The box was marked for a 4lb drive pulley. Not in the case with the PA alternator due to the max rmp limit.

Still waiting on the idler pulleys. I decided to replace all of them on the front belt due to the higher tension the belt will have (assuming it will fit with the larger alternator pulley).

I should replace the belt but the original is in great shape. No cracks or signs of wear but that does not mean it is any good after 50k miles.

ausie
02-09-2012, 06:27 PM
Everything is installed but the belt. Had to order a longer belt due to the alternator pulley change.

Almost thought I could get the stock belt on, even removed the stop tab on the tensioner. It it was even possible to get the stock belt in place I would have removed it and ordered the longer belt any way (would have been too tight).

I did consider replacing the inner serpentine belt, that job is involved and can wait since I am eager to get the car on the road again. The inner belt looks in good shape so I will leave it as is for the time being.

For stock pulley set up and a 3.2" alternator pulley the belt length need to be 1" longer. Metco had a reference chart for the belts for different combo of lower and upper pulley and a reference note how much to add to belt length for the alternator pulley sizes. I calculated 0.943" as the difference on belt wrap for the 3.2 compared to the 2.6 (metco referenced 1" for the 3.2).

Went with a Dayco Belt 5080760 which looks about the same as the Gates k08 series and Gatorback 408 series.

Just have to remember to reflash the ECU and drop the redline to stock, as well as return the high speed fan back to its original settings.

Snoopy 777
02-09-2012, 07:41 PM
I think there is less working space in the GT500. I am sure things may be easier with the cooling system hoses removed, but at least it was not that bad removing the alternator without dumping the coolant.

Where is the alternator on the GT500? Is it in the same area?

I sure hope the PA alternator will not fail prematurely as others have found out.

I just got the 3.2" pulley today. The box was marked for a 4lb drive pulley. Not in the case with the PA alternator due to the max rmp limit.

Still waiting on the idler pulleys. I decided to replace all of them on the front belt due to the higher tension the belt will have (assuming it will fit with the larger alternator pulley).

I should replace the belt but the original is in great shape. No cracks or signs of wear but that does not mean it is any good after 50k miles.



The GT500 alternator is on the drivers side, at the bottom. Under the PS pump and in front of the oil cooler. Packed in tight.

I didn't change any pulleys, just a straight forward replacement.

ausie
02-10-2012, 11:25 PM
The GT500 alternator is on the drivers side, at the bottom. Under the PS pump and in front of the oil cooler. Packed in tight.

I didn't change any pulleys, just a straight forward replacement.

That is the same location for the terminator. Does the GT500 have a dual belt drive system (outer supercharger drive and inner surpentine accesory drive)? My guess is that it does.

Snoopy 777
02-11-2012, 07:44 AM
Yes 2 belts. There was other stuff it the way if I remember correctly? And some bracket piece that made removing one bolt near impossible to get at.

As you can see by the pics there were tons of hoses, wires and pipes to get around.

http://i670.photobucket.com/albums/vv61/fastestshelby2/Alternator/DSC08262.jpg

http://i670.photobucket.com/albums/vv61/fastestshelby2/Alternator/DSC08265.jpg

http://i670.photobucket.com/albums/vv61/fastestshelby2/Alternator/DSC08266.jpg

http://i670.photobucket.com/albums/vv61/fastestshelby2/Alternator/DSC08268.jpg


I also had to remove the front of the sway bar to get it out.

Problem was releasing these special bolts.

Had to replace 4 of these bolts at $9 each!!!

http://i670.photobucket.com/albums/vv61/fastestshelby2/Alternator/DSC08270.jpg


.

ausie
02-11-2012, 10:19 AM
Holly **** Charlie Brown:eek:,
Removing the alt in the GT500 looks as difficult as replacing the surpentine belt on the terminator. Removing and installing a new alternator in the terminator is a walk in the park compared to that.

Snoopy 777
02-11-2012, 08:26 PM
That's why I'm keeping a very good eye on battery voltage since it sits so much.

ausie
02-12-2012, 01:07 PM
I would agree.
Mine sits alot too. Was considering getting a battery tender.


Still waiting for the belt to come in. Should have ordered it online instead of the local shop. I could have saved a few bucks too.

Since I have been hearing some noises and not sure if it was the alternator, water pump, or clutch, I decided to take off the SLP cat back and install the 04 OE exhaust. I have too many spare parts in my garage along with many unpacked boxes of stuff from the move. I can now rule out the outer belt ilder pullies since I replaced them with double bearing metco 90mm pullies.

Since the spring season may be a wet one, I decided to install the BBS wheels since the Toyo's are excellent in wet weather.

Snoopy 777
02-12-2012, 03:08 PM
Battery Tenders are a good investment.

I have 3 of these that I rotate between our cars, trucks, 4 wheelers and jetski's.


http://www.northerntool.com/shop/tools/product_200332201_200332201

ausie
02-14-2012, 07:27 AM
I picked up the belt yesterday. Did not take long to install. Considering the surface of the grooves, it looks very much the same as the OE belt so I will hold on to it in case I have to replace the alternator again ( will go the 160Amp route on ebay, that one uses the stock alt pulley).

Seems to be a good fit. I will not be able to install the SC pulley cover due to the oversized metco idler pulleis. The reason why I installed the siglent 04 exhaust is to hear if the odd noise returns. So far it has not and it may have been the OE alternator crapping out or one of the idler pulleys was breaking down.

Even with more back pressure from the stock exhaust, the car is stronger than ever. The wife does not like the SLP due to drone. She just does not get it. When you get on it, all you hear is the supercharger and a little bit of engine. Brings me back to the day I bought it :rotf: