Alternator ampage

Can anyone tell me the correct ampage for the alternator on a 351C 2V.

I called a supplier in the UK and they have told me there are 2 options of 61amp or 70 amp. I was told to measure across the rear of the alternator. There are two sizes 5 1/4 inch means its a 61amp and 6 1/2 inch means i need a 70 amp. I looked on NPD website via a link from a previous post on this forum and that took me to a 55amp alternator.

http://www.7173mustangs.com/thread-replacment-alternator

So now i am confused.

The reason i am asking is because i have a brand new battery. The battery will not hold any charge. After charging the battery and running the car for around 10 miles and then switching the ignition off the battery is completely dead when i try to start the car again straight after switching off the car.

Whilst i am replacing the alternator i may as well replace the regulator at the same time. Can anyone tell me which regulator i should purchase.

Even without an alternator the battery should last quite a while, without fuel injection these engines don't take much power. Have you checked your ground cables?

As for the stock alternator I'm not sure. I replaced mine when it went bad with this one. http://www.themustangshop.ca/product/11445207/658143

Here are the 72 AMA Specs for alternator applications. I have not heard of a 70 amp application in the US. It may be unique to export though. Hopefully these help.

72 alternator - AMA spec.docx

Voltage Regulator:

https://www.npdlink.com/store/products/mustang_voltage_regulator_alternator_electronic_replacement-100810-432.html

For original look, replace the cover with 'concours' one.

There was an option for HD battery which I think gave you a larger alternator. Also if your car had Power Windows, Rear Window Defogger it came with the 70 amp alternator. My Mach 1 has the big one but nothing listed on options referring to HD battery it was part of the options that I picked that did the upgrade. There are different wire harness for each I believe. Just the short one from the alternator to the regulator. I will not hurt anything to have the larger one just won't have to work as hard to keep charged. It should be stamped on the top of the alternator what AMP it is might have to brush it to see it. Originals had stamp replacement might not. Your local parts store should be able to check your system for free and tell you what is up. You will have to go in with full charge in the battery for the check. They can check the battery and alternator in the car while running.

With your battery going dead sounds like you have something shorted maybe draining the battery. I would unhook the battery when not driving to prevent possible fire. Make sure all fuses are in place and proper size to prevent melting down something. Previous owner of one of my cars did some crazy things and had melted the AMP meter in the center gauges. It got so hot it melted the housing and ran down.

did u ck the voltage across the battery without motor running and running ??

off = 12 to 12.5v, running 13.5+v. i just got a really nice 100a alt on ebay and chrome for $100 (us). keep engine bay correct is not something high on priority

for there are enough things changed already to off factory.

So i had battery and alternator checked. Looks like the alternator is the culprit. Alternator is pushing the bare minimum through it. Trying to start a 5.8L with bare minimum going through the alternator is a no-no.

David mentioned it may be a short; After removing & charging the battery again and taking the car to a local garage to diagnose the problem i turned off the car and started it again at the garage. This time it started after turning it off. So as mentioned above i took battery off which meant moving the wires. So maybe i have a ground issue on top of alternator needs replacing.

I think i am going to replace the alternator & regulator at same time. With the new battery i should be trouble free in that area for some time. When i fit new parts i will undo all wires and sand them to be sure the problem does not recur for a while.

Thank You for all your help

Starting a car does not involve the alternator; the battery provides the amperage to the starter motor. Only when the engine is running (and key in RUN position only) does the alternator/voltage regulator provide power to the battery and the car.

A fully charged battery, in good condition, will provide enough energy to start a car several times and drive more than 10 miles, unless there is a lot of load (lights, heater, stereo, etc) or a short.

Did your garage perform a load test on your battery? New doesn't mean it doesn't have a bad cell, or other problems.

A fully charged battery, in good condition, will provide enough energy to start a car several times and drive more than 10 miles, unless there is a lot of load (lights, heater, stereo, etc) or a short.

Did your garage perform a load test on your battery? New doesn't mean it doesn't have a bad cell, or other problems.

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Yes Don the garage performed load test on the battery. I feel certain there is a short due to the car now starts after removing/replacing battery with the movement of wires during the process.

The cars starting process had no issues. However, when i dropped it off to have all the wheels removed and refurb the wheels the starting issue began after that. So i am wondering if the jacking process and standing on jack stands made the problem occur.

Naw...the tire company stole your charge::devil::...you did give them your charge card, right?

Naw...the tire company stole your charge::devil::...you did give them your charge card, right?

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