Single-Wire Alternator Questions Again

[Sledge]

Folks:

I've got a Powermaster 100-amp single-wire alternator in my BDR. I do not have a stereo or other massive power drain, just the juice required to run the engine, fuel pump, lights, and the two aux cooling fans.

I don't understand what my voltmeter should be reading when the car is running. Sometimes it reads 15 volts or so, other times it reads less than 12. I drove my car down to San Diego (in daylight, lights off), and while cruising on the freeways (the aux cooling fans were off) I watched the voltmeter go from 15 slowly to 12-, then return slowly to 15 volts 15-20 minutes later. It did this two or three times during the trip.

When I started the car to bring it home it initially read 15 volts, but for the last 70 miles home it read 12- volts for the entire distance--no cycling, even with the fans coming on and off (traffic jam). Again, this was daylight with lights off. When I next started the car (a couple of minutes after getting home) and drove it for a couple of miles, the volt meter stayed at 12-.

Are the above indications normal for BDR installations? I'm just looking for feedback from other BDR owners with single-wire alternators as to what "normal" volt indications are or should be; just a baseline starting point. I've asked these questions before but most responses tied the variation in the voltmeter to heavy electrical loads, which weren't present in this recent trip as the lights and fans were off. So I guess I'm cross-checking against previous responses, and looking for new additional input if there is any aout there.


If it isn't normal then I've either got a gauge problem or another failed or failing alternator, or maybe a wiring problem, so I've got more troubleshooting to do. I've got 1100 miles on the car. Armond hasn't been able to help me much in ths regard, although he replaced the first alternator under warranty, and I'll be talking to Reg on Monday if I can get him. I haven't invested in an alternator output meter yet, was hoping I wasn't going to have to.

Thanks and cheers

Bill

[392cobra]

Bill,
You might have already done this but have you had the battery tested ?

[Sledge]

Fred:

No I haven't. The battery has been working fine for the last 1100 miles so I didn't think I needed to. I've already had to replace one alternator, so I've been assuming that's where the problem has been.

Does your car have a single-wire alternator and a voltmeter? If so, are the indications I've described different from yours?

Thanks

Bill

[harley]

Sledge

I have a single wire alt - but i don't think it matters much - your readings are not normal - the bare battery should be about 12.6 volts and when running you should expect between 13 and 15 volts - this would indicate a charge on the battery

It is a pretty simple circuit - it could be the battery, alternater or something intermit that is is taking a very healty slug of current or shorting to ground

If i had to guess, i would guess the alt has a thermal problem and does not charge when hot --- I don't know where it is mounted and how much heat it is picking up - but the easy checks would be get it hot and take it to the local parts place and they can test it --

good luck

jim

[Sledge]

Jim:

Thank you! I thought that it should read around 15 or so volts pretty near all the time if the darn thing was working, and certainly more than 12.6 or so.

So here I go again.

I don't think the battery is the issue as it cranks the engine just fine. If it had a short between cells I would have thought that it wouldn't crank the engine. Is there a more sophisticated battery test that should be done, or other battery fault that could be contributing to this?

Also, when I started the car this morning, cold, the alternator still did not come on line. So I don't think it is a heat problem.

Time to take it to an expert I reckon.

Any other suggestions would be welcomed!

Thanks

Bill

[trularin]

Have you done a search on the posts?????

[Sledge]

Yes

Bill

[Cashburn]

I've had problems with aftermarket 1 wires before. They sometimes do not energize properly and/or their internal voltage regulators can be screwy. Find a specialized starter/alternator shop and let them test it... Pep Boys and Autozone testers never spin 'em enough to properly test the aftermarket 1 wires.

[Frank Messina]

Sledge,
My daily driver (Cadillac Eldo TC) does exactly the same thing. It's one of the reasons I swore to myself to not use a 1 wire on my Cobra and am using a Ford 3G. This is not the first GM product I've owned that has exhibited this condition either. Makes you nuts watching the volts drop but it seems to keep going with no unusual battery problems. Sorry I don't have a silver bullet for you.
Frank

[Boudy]

I have not used the one wire alternators on a Cobra. However, my impression is that your alternator may be inconsistantly charging. It should read 14 or so running and 12 not running. If the meter drops to battery voltage (12) while running, I'd suspect the alt. Try this: Get a $10 volt meter and measure the battery while the car is running and the gauge says 12. If the volt meter confirms that the gauge is correct, I'd take it to a shop to have the alt tested.

Boudy

[trularin]

Start the car, while running disconnect the battery positive terminal.

1. If the car dies, the alternator is NOT charging.
2. If the car RPMs goes up, the battery or car may be pulling it down.

Read the battery with the terminal disconnected. If it is 12.8 to 13.2 volts, you battery is probably fine.

Read the voltage at the wire you connect to the battery. it should be around 14.2 to 15.1 volts. If it is over this, it may be over charging the battery. If it is less, I would have the alternator checked. It can put out just the minimum and not charge the battery. This is caused by either the feedback wire ( self excitation ) not connected properly to the battery charging system. Bad regulator ( not grounded well in the case ) or winding failure ( I think, it's hard to remember this stuff when you haven't used in in several years ).

Single wire or self excitation works as long as all of the criteria are met. Personally I use the three wire setup as designed by Ford. It is a no brainer for anyone if they just settle down when working on it.

Just my $0.02

[Sledge]

Tru, Boudy, Frank, Cashburn:

Thank you for the responses and ideas. I really do like this forum because of the people willing to help others.

The alternator is simply going off line occasionally, then coming back on.

I've checked the wiring out and found loose, corroded, poor-contact-making wire terminations at the battery terminal of the starter solonoid, which is where the charge wire from the alternator goes. We also found a loose wire at the battery switch. In spite of cleaning/tightening/fixing the terminals, the volt meter (confirmed by a separate volt meter) showed the alternator would come on line, then go off line, then come back on line again. Independent of fans, lights, etc.

I also installed a new (gel) battery because I wanted to anyway, seemed like a good time to do so. No change to the on-again, off-again charge output from the alternator.

I talked to Powermaster today and they say this is definitely not what this alternator should be doing--once on it should stay on without cycling. I've taken some pictures of the alternator and installation and have forwarded them to Powermaster (per their request) and will be talking with them some more tomorrow. Unless they come up with something I haven't seen (easy enough to do since I'm both stupid and blind) I may have had a couple of bad alternators in addition to or because of the wire terminations.

I haven't taken the alternator in yet to confirm the fault, but that appears to be the next likely step. And then a new alternator.

Hope this helps someone else, and thanks again for the responses.

Bill

[chuckmynatt]

Sledge,
I installed a 100 amp Powermaster single wire on my Cobra a while back and I have not any problems. One "quirk" I have found is that the voltage right after start will be around 12 volts and will remain there until you rev the engine up to about 2000 rpm. The voltage will then swing up to around 14 volts and remain there for the rest of the time regardless of rpm. Mine seems to need that initial rev to get it up on line and it's good to go after that.

Chuck

[Ron61]

I did see one of those brand alternators do exactly what Sledge said his is doing. After fighting with checking everything, we took it off his car and to an alternator/starter shop here and they put it on a tester. It did the same thing and the company sent him a new alternator. I don't know much about the single wires, but I think they said the exciter in his was bad. It would kick on at about the 2000 RPM like Chuck said and then a minute or so later go off line.

Ron

[Nor Cal Al]

I had a vintage alternator built for me and had a pack put on the back to make it a 1-wire (ie., add-on regulator). I have underdrive pullys and they said the charge may not turn on until it gets rev'd once. My experience has been that the charge will turn on, run at about 14 volts and come down or shut of when the battery is charged providing there is not a great load on. Mine runs for quite a while because the Beast does not get out once a weekend or maybe everyother weekend. Less over the winter.

My first pack failed and I had 18 volts to the battery.

[Sledge]

Al, Ron, and Chuck:

Thank you for the adding some more experience to the single-wire pool. For a while there I thought I was going nuts, but Ron's experiences were good to hear in a misery-loves-company sort of way.

I drove #168 up the Angeles Crest Highway today, and back, and the alternator did not come on line even once--battery all the way. And I assure you I was frequently and at length above 2000 RPM. The alternator is off the car tonight and going to Powermaster tomorrow. The way things are going I may buy an extra alternator just to have a spare.....

Thx and cheers

Bill

[Boudy]

Cool. Glad to see you got it figured out. Keep us posted when you install the new one.

Boudy

[Sledge]

Boudy:

Put the new one in (another Powermaster) today and it worked like a champ. Did lots of stop-and-go driving with fans on most of the time, never indicated below 14 volts.

I'm waiting to hear what Powermaster finds with the one I sent back to them. I suspect the loose and intermittant connections at the starter solonoid did it in.

Cheers

Bill