1 wire alt.

Anonymous-0 · Dec 20, 2008

Do single wire [GM]altenators drain batterys when not used regulary.My battery in my 36 goes dead in about 3 weeks.I just replaced my 6v lead acid batt with a optima thinking the battery was at fault.If the alt does drain the batt what can I do to prevent it? Thanks Phil

Bob · Dec 20, 2008

Try completely disconnecting the alternator. (Tape up the leads for safety.)

If the battery stays up, you'll know for sure it's the alternator.

Have it checked out/updated, or replace it with a 3-wire setup. (IMHO, some of the one-wire units seem to be prone to discharging the battery while the machine sits unused.)

John T · Dec 20, 2008

Phil, I'm smarter on generators then alternators, but can still tell ya some of the one wire alternators do cause some minor low amperage trickle discharge when setting idle buttttttttttt if the alternators is okay????, I dont see it as causing a battery (which is otherwise okay, no internal shorts or discharging) to discharge in like 3 weeks. As Bob notes simply unhook it n see if the discharge stops.. Many auto parts houses can test alternators at no charge..

John T

old · Dec 20, 2008

Simple answer is yes most do drain battery over time because they self excite and do not disconnect 100% so it has a small amp draw at all times. My self I would switch over to a 3 wire can never look back and also never have that problem again unless of course it goes bad but if you get it at the right place you can also get a life time warranty on it. I buy mine from O'reilly's auto parts and they have the life time thing
Hobby farm

Janicholson · Dec 20, 2008

As noted below, they can and do drain bats. Putting a heavy (60 amp rated) switch between the alt fat wire, and the amp gauge will also keepmit isolated when not in use. JimN

mkirsch · Dec 20, 2008

Dad's Super M has a 1-wire alternator on it. Sits for months at a time during the winter. Fires right up in the coldest weather. In fact it cranks over like crazy.

There is something wrong with your alternator.

Janicholson · Dec 20, 2008

I agree. The internal VR in some of the one wire systems draws about 200ma (if measured across an open battery terminal) others draw more like 500ma or more. They are not all the same. Putting a ma meter on the alt output wire will tell the story. JimN

JMOR · Dec 20, 2008

(quoted from post at 17:29:24 12/20/08) I agree. The internal VR in some of the one wire systems draws about 200ma (if measured across an open battery terminal) others draw more like 500ma or more. They are not all the same. Putting a ma meter on the alt output wire will tell the story. JimN

And compare those numbers to the standard GM 3 wire setup & see why many recommend sticking with 3-wire. The standby draw on those is 0.75ma.

75A-H battery, divided by 0.75ma divided by 24hrs/day=4,167 days.
Probably self-discharge on the shelf before that.

Hugh MacKay · Dec 20, 2008

Phil: Reading this discussion, there must be a wack of alternator out there having something wrong with them.

I agree with Old, convert it to 3 wire and leave your troubles behind.

Bus Driver · Dec 20, 2008

No need to guess about what is draining your battery. Remove the grounded battery cable. Then hook a voltmeter between that cable end and the battery terminal that formerly had the cable. ANY electrical draw will show as a voltage. Then disconnect one thing at a time until the draw ceases. When the voltmeter goes to zero, that item is the problem.
This meter is a bit pricey, but well suited for vehicle electrical testing.
Hoyt

El Toro · Dec 20, 2008

Install a master switch in the ground cable and this will isolate the battery from being grounded. The military has used this for years. Hal

John M · Dec 21, 2008

Plumb a normally open oil pressure sending unit into the line to the gauge. Run your wire from the alt to that, then the gauge. When the engine runs, the circuit is closed and the alt charges, not running its open and doesnt drain the battery, and its hidden and out of the way, and no extra wires or switches to install.

JMOR · Dec 21, 2008

(quoted from post at 09:47:08 12/21/08) Plumb a normally open oil pressure sending unit into the line to the gauge. Run your wire from the alt to that, then the gauge. When the engine runs, the circuit is closed and the alt charges, not running its open and doesnt drain the battery, and its hidden and out of the way, and no extra wires or switches to install.

Is that an idea, or have you actually done it? Reason for asking: alternators can put out 50 to over 100 amperes (model dependent) and a typical oil pressure switch turns on a milliampere 'idiot' light bulb.
Just asking.

Some manufacturers (MF diesel for one) use an oil pressure switch to power the field Excite line on 3-wire alternators at about 4 amps. But that is not the 1-wire type being discussed here.

John M · Dec 22, 2008

Got two like that! One has been on there for Im guessing about 12 years, the other Dad put on in 1978 when we bought the tractor, but we have had other equipment that we have bought and done that to. Theres many tractors and other equipment around here that othrs have done the same thing to, and so far so good. As soon as Santa brings my new camera, Ill post some pics.

JMOR · Dec 22, 2008

(quoted from post at 07:21:39 12/22/08) Got two like that! One has been on there for Im guessing about 12 years, the other Dad put on in 1978 when we bought the tractor, but we have had other equipment that we have bought and done that to. Theres many tractors and other equipment around here that othrs have done the same thing to, and so far so good. As soon as Santa brings my new camera, Ill post some pics.

I'm impressed! Fine little switches.

1 wire alt.

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