Electrical Help

[PhillipM]

My alternator is not charging the battery. I think I have been facing this issue for a very long time. I had this issue during homecoming. Today I put the second Alternator and voltage regulator on the car, still same issue.
This is what I have done so far.
1. New Alternator
2. Had the Advance Autoparts test the new alternator before I took it home.
3. New Regulator
4. Tested new alt/regulator with a volt meter and had Advance Auto parts test it as well. This is after I excited the alternator. Between 2000 and 2500 rpm, no voltage increase.
Could I have a grounding issue?
If I take a voltmeter and remove the red wire from the alternator, will I see voltage if I reconnect battery? I am trying to determine if I have a broken wire.
I am trying to determine the best troubleshooting techniques. Other that this issue the car runs great. Also, no blown fuses and all other electrical components work fine.
Phillip

[Aggressor]

Phillip
1st Refresh our memories as to what alternator and regulator configuration you are running.

Check for grounding issues first and then check the continuity of wire connections.
Also if you have aluminum mounting brackets for your alternator mounts - especially billet types - you may have to run a separate ground cable to the alternator housing. I worked on a customer's 53 Chevy street rod a few months ago. The battery terminal showed 12.5 volts prior to starting, jumped to 13.7 when the excitor kicked in, and then steadily fell to 10.5 on a short hop around town. About made me nutz until I called Powermaster and the tech asked about the mounts for the alternator. Separate ground installed - no more problem. Also if you're running a separate regulator mounted on glass, ground the housing to the frame as fiberglass is even a much worse ground than aluminum. Make sure your engine is grounded to the frame also.

- Geary

[Slither]

if you have aluminum mounting brackets for your alternator mounts - especially billet types - you may have to run a separate ground cable to the alternator housing. I worked on a customer's 53 Chevy street rod a few months ago. The battery terminal showed 12.5 volts prior to starting, jumped to 13.7 when the excitor kicked in, and then steadily fell to 10.5 on a short hop around town. About made me nutz until I called Powermaster and the tech asked about the mounts for the alternator. Separate ground installed - no more problem. fiberglass is even a much worse ground than aluminum.

- Geary

Not sure I follow this... aluminum is an outstanding conductor, commonly used in the power-distribution industry. In fact, my house runs on it... underground aluminum cables. Most of yours do as well! It seems that paint or some other non-conductive bushing would be the cause of this, rather than an aluminum bracket... unless maybe there was some serious corrosion at the mating surfaces.

The aluminum bracket is not the ground, but becomes part of the ground node along with the engine, frame,and anything else connected to that part of the circuit and the negative battery terminal. Such is the wire that you used to bypass the alternator bracket.

What did the tech say caused the issue? Is the billet stuff a non-conducting alloy? That would do it...

[mkassab]

Hi Phil.... I've heard of this problem before. In fact, I already purchased a ground strap for the Cobra build.... (from engine to frame).... here's a link. http://www.summitracing.com/parts/TAY-148014/
Even if this isn't the issue, it sure can't hurt. Mark

[JeepSnake]

Not sure I follow this... aluminum is an outstanding conductor, commonly used in the power-distribution industry. In fact, my house runs on it... underground aluminum cables.

Paul, you are right: aluminum is a fine conductor. But, the sticking point is that aluminum sucks in regards to making a good connection to it. It is extremely reactive - it is more quick to oxidize than iron. Every piece of exposed aluminum in your engine compartment has a thin layer of non-conductive aluminum oxide on it; if that's not penetrated in the connection, no conductivity. (Conversely, this thin oxide layer protects the aluminum underneath; rust does not do this for iron. That's why an iron piece will rust away faster, even though it's not as reactive as aluminum.)

And then there's the issue of keeping the connection once you've established it. Remember the fiasco of aluminum building wire in the '70s? The connections loosen up over time, corrode, build resistance, heat, arc, burn the house down... I know the industry tried various types of special connectors and even copper-plated aluminum wire in an attempt to get the connections to last over time, all without much success.

You service drop cable (about a 40% chance it is Southwire cable manufactured on a production line that I installed, BTW! Please go buy more! We need the business!) is indeed aluminum, but you'll see that it stops at your breaker box. From there on you'll have copper. You'll also see that where the aluminum is lugged into the box that it has gobs of conductive joint compound on it to increase condutivity, lube the lugs, and protect the connection from corrosion.

So, even though the aluminum itself is great, the various intermediate connections can kill you. A ground wire straight to the alternator case is an easy way to avoid a lot of potential headaches caused by the connections. (Also, always use a serrated lock washer for your ground wire connections - you know, the washers that look like a Skil saw blade. At the alternator case, these will cut through the oxide layer; at the frame, they'll cut into the steel for a better connection as well.)

[mkassab]

Phil, I agree with all the above on Alum. and Oxidation. So her's what I would recommend. Go to Lowes or Home Depot electrical section and buy a small tube of Ox-Gard. This is "grease" like stuff that prevents alum oxidation. Then clean any area you have alum connections, add OX-Gard, then clamp tight. I'd also run a seperate ground wire from the alternator.... I'm just not sure the gauge size you should use? My guess would be is to use the same size as the copper + (positive) coming from the alternator. One thing I do know is too big is much better than too small.

Mark

[mkassab]

Phil... I may missed it, but did you have your battery checked? Maybe something wrong on that end?