58mark

iTrader: (3)

I've tried three different alternators, including a brand new powermaster, an all three put out random, fluctuating amounts of charge. Sometimes it will read 13.3 (still a little low) but usually its hovering around 10. What could cause this if the alternator is bench testing as being good? I've already replaced the pigtail that plugs in the back. Could it be a groundside resistance problem, and if so, how do I fix that? I did a groundside resistance test and it shot back a 4, which I hear is a little high.

Edwardgp

I run many grounds. I have one that runs from the top alternator bracket to the chassis. Here it meets up with the ground for the battery to chassis ground. I have both cylinder heads grounded, which is recommended when you use a MSD ignition. I also run two engine to firewall grounds. I don't know if this will help you but it is worth a try.

58mark

iTrader: (3)

OK, update. I added a ground from the battery to the alternator case, no improvement

I added a ground from the body of the car to the alternator case, no improvement

I removed all the front side brackets that I had powdercoated just in case there was a grounding issue there. I filed off all the powdercoating any place they cam in contact with a bolt or the block. No improvement

Even though this is a brand new alternator and was bench tested before it was shipped, I had it bench tested again. It failed because it's only putting out 11.4 volts. Could there be something about my car that is killing alternators? I have three of them doing the exact same thing.

58mark

iTrader: (3)

OK, this is strange. The powermaster alternator tested as bad, but the original alternator that I replaced it with (because I thought it was bad) tested good, but because I had a problem with it, Autozone gave me a replacement anyway. This new one seems to be fine. My mechanic's theory is that the bad grounding due to the powdercoating killed the first three alternators, and after this morning when I took it apart and checked all the grounds, this new alternator should be fine, but I'm going to keep a close eye on it anyway.

Tibo

iTrader: (15)

Could be partially the result of a poor connection such as not having it touching bare metal and instead powder coat. Could also be because the battery is bad or was drained and the alternator was working overtime to charge it. Could be a power wire that is too small or cut/frayed. I think stock wire harness uses 10 gauge, which to me sounds too small. For grounds ensure that you have as a minimum, ground via cylinder head, and engine block, and battery to chasis. I believe that stock battery to chasis ground is 10 gauge which again in my opinion is too small.

58mark

iTrader: (3)

I'm hoping it was a grounding issue, and I've since removed all the powder coating from any part of the Brackets that touch the block, the alternator, or a bolt.

Jonesyfxr

iTrader: (2)

Grounds are by far the most important connections in a 12 volt system. Nine out of ten wiring problems are ground related.......ask how I know. Twenty years of installing car audio systems, wiring limos and emergency vehicles.

Always make sure you have a clean metal to metal ground and you'll alleviate TONS of headaches.

I'd bet your powder coated brackets are what killed you power master.

If you want to know how important grounds are, just disconnect your ground wire and complete the circuit with a volt meter.