Measuring alternator amperage???
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Laughing Gas
Joined: Feb 2004
Posts: 1,080
Likes: 1
From: Elsinboro, NJ
Measuring alternator amperage???
Is there a way to do this without taking it to a shop and having it tested? You know more than the Good/Bad test? I spoke to a shop locally that rebuilds alternators and starters, and the guy was telling me that our 130 amp alternators generally put out about 43-44 amps at idle/low RPM's.
I am getting ready to put on a H.O. and it says that at idle it puts out 100 amps. The snow plow motor is killing me with my lights dimming every time I lift the blade. The one on the truck now is less than a year old and in good shape, just hoping that this may be the answer to my problems, not to mention help run the inverter....
I was just trying to figure out if there was some test to run and see the data for myself...
I am getting ready to put on a H.O. and it says that at idle it puts out 100 amps. The snow plow motor is killing me with my lights dimming every time I lift the blade. The one on the truck now is less than a year old and in good shape, just hoping that this may be the answer to my problems, not to mention help run the inverter....
I was just trying to figure out if there was some test to run and see the data for myself...
Junior User
Joined: Sep 2005
Posts: 75
Likes: 0
From: Fort Rock, OR
If you have an ohm meter you could check resistance in your battery cables, and supply cables to your plow. Clean all connections.
The alternator will only put out 100 amps if the system requires it, if everything is working properly.
Stock alternator should put out about 25 amps at idle after glow plugs have cycled and alternator has re-charged batteries after starting. Also no heater fan, lights or other accessories on.
The alternator will only put out 100 amps if the system requires it, if everything is working properly.
Stock alternator should put out about 25 amps at idle after glow plugs have cycled and alternator has re-charged batteries after starting. Also no heater fan, lights or other accessories on.
Postmaster
Joined: Jan 2009
Posts: 2,667
Likes: 1
From: Glen Rose,Texas
We have seen alot of problems with over the counter alternators.I would suggest buying one from a true rebuilder and you will get a better built alt.He can build it to your specs.
Put your meter on the positive lead and see what it is putting out.
Put your meter on the positive lead and see what it is putting out.
Thread Starter
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Laughing Gas
Joined: Feb 2004
Posts: 1,080
Likes: 1
From: Elsinboro, NJ
Yeah, we talked about him rebuilding mine. He said the only problem is at idle. He said there is nothing they can do within the idle limits. They can take a stock 130 and make it a 200 but it is only 200 at 3000rpm's. He said it will still only put out around 40 amps at idle.
Junior User
Joined: Sep 2005
Posts: 75
Likes: 0
From: Fort Rock, OR
I've seen several alternators on '00 to '02 put out 85 amps at idle while the glow plugs were cycling and batteries recharging after start up.
I've got a fluke A/C D/C amp meter that I clamp onto the output wire on the alternator.
I'm no alternator expert, I'm just reporting what I've seen on systems functioning normally.
I'd check resistance in your battery cables and don't overlook the grounds.
Good luck.
I've got a fluke A/C D/C amp meter that I clamp onto the output wire on the alternator.
I'm no alternator expert, I'm just reporting what I've seen on systems functioning normally.
I'd check resistance in your battery cables and don't overlook the grounds.
Good luck.
Posting Guru
Joined: Apr 2000
Posts: 1,345
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From: NorCal
Just like Harris, I have a Fluke AC/DC Amp meter. It's a clamp that goes around the power lead leaving the alternator. It shows how many amps are running through the conductor via induction. There are a lot of less expensive brands out there (Greenlee for one) that work just as well.
Thread Starter
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Laughing Gas
Joined: Feb 2004
Posts: 1,080
Likes: 1
From: Elsinboro, NJ
Sounds like it may be a nice tool just to have around....Thanks guys, I'm going to look into one...
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Mountain Pass
Joined: Sep 2007
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From: Alaska
Just like Harris, I have a Fluke AC/DC Amp meter. It's a clamp that goes around the power lead leaving the alternator. It shows how many amps are running through the conductor via induction. There are a lot of less expensive brands out there (Greenlee for one) that work just as well.
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Postmaster
Joined: Apr 2006
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From: CA Bay Area
Don't the "clamp around the cable" ammeters work with AC only? I am not electrician, but that is what I was told.
Dimming lights when the plow lifting would indicate poor cable connections to the battery. There is no way an alternator can keep up with such demand and that what battery is for.
I do have 1HP electric motor for my dump bed and I think 2 HP on my winch I hardly see voltage drop when I push the switch. Good cables make the trick.
Dimming lights when the plow lifting would indicate poor cable connections to the battery. There is no way an alternator can keep up with such demand and that what battery is for.
I do have 1HP electric motor for my dump bed and I think 2 HP on my winch I hardly see voltage drop when I push the switch. Good cables make the trick.
More Turbo
Joined: Mar 2007
Posts: 636
Likes: 7
From: La Mesa, Ca.
The alternator has a voltage regulator that controls what amperage is needed to maintain the voltage. The Alt, doesn't "put out" per SE, but rather responds to a low voltage condition. The alternator can only work at rated capacity if it is in the proper RPM for that alternator, usually above 1500 RPM. Any poor connections in the cabling, or marginal batteries will make the whole system perform poorly. The key here is the voltage of the system when you add a load.
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Laughing Gas
Joined: Feb 2004
Posts: 1,080
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From: Elsinboro, NJ
Lucky for me friend had an amp meter. Truck running with glow plugs on drew about 46 amps. When the plow was lifting the amp draw was 72 at the altenantor wire. At the plow motor it was 134 amps on lift. Took off all the connections and cleaned them with the same results. Truck running looks like the altenantor was putting out 22 amps continiously.....
Now when the plow would lift the battery voltage would drop from 14.8 volts to 13.0...
Now when the plow would lift the battery voltage would drop from 14.8 volts to 13.0...
Mountain Pass
Joined: Sep 2007
Posts: 244
Likes: 4
From: Alaska
Voltage will drop when the power draw on the system exceeds the maximum power output of the alternator.
Posting Guru
Joined: Apr 2000
Posts: 1,345
Likes: 0
From: NorCal
Don't the "clamp around the cable" ammeters work with AC only? I am not electrician, but that is what I was told.
Dimming lights when the plow lifting would indicate poor cable connections to the battery. There is no way an alternator can keep up with such demand and that what battery is for.
I do have 1HP electric motor for my dump bed and I think 2 HP on my winch I hardly see voltage drop when I push the switch. Good cables make the trick.
Dimming lights when the plow lifting would indicate poor cable connections to the battery. There is no way an alternator can keep up with such demand and that what battery is for.
I do have 1HP electric motor for my dump bed and I think 2 HP on my winch I hardly see voltage drop when I push the switch. Good cables make the trick.
Postmaster
Joined: Dec 2010
Posts: 2,951
Likes: 4
From: Gary,Indiana
Lucky for me friend had an amp meter. Truck running with glow plugs on drew about 46 amps. When the plow was lifting the amp draw was 72 at the altenantor wire. At the plow motor it was 134 amps on lift. Took off all the connections and cleaned them with the same results. Truck running looks like the altenantor was putting out 22 amps continiously.....
Now when the plow would lift the battery voltage would drop from 14.8 volts to 13.0...
Now when the plow would lift the battery voltage would drop from 14.8 volts to 13.0...
