Killed my alternator

[dk8019]

I took a look through some of the similar threads here, but can't find if this might be the true cause of my problems with my alternator.

My wife and I took the M109 down to Kentucky for the Thanksgiving weekend, it was a hit, we slept in the back of it, while connected to a 120V outlet outside her parents house, they have a small place, and no spare rooms that weekend, so it worked out well. The Deuce did wonderful the 300 miles down and back, it was a great trip.

Well on the way back my wife was using a small electric heater connected to a 1500 watt inverter, the inverter did fine it seems, but I noticed about half way through the trip that the battery gauge now showed in the yellow instead of the green. We made it home without any issues but I was never able to get it to come back into the green, even with everything off. I run the numbers, and it looks like there's a good chance running the inverter near it's max load could have exceed the output of the alternator. (24V or so * 70A = 1680W or so, roughly the draw of the inverter at full load)

So my question is did my poor choice in inverters kill my alternator? I have a feeling it did, as the voltage output is pretty much at battery voltage. I just want your opinions, did my alternator die because it was time, or did I kill it with too much load? I've ordered another regulator for it, it seems in good shape otherwise from what I can tell. Thanks for the help!

 

[FMJ]

Unhook your batts, and check the output of the Gen with a meter, (engine running) you should see 25 volts or so depending on where the regulator is set...

Where you hooked to one battery to run the inverter? If so you might want to try charging the battery you had it connected to.

 

[dk8019]

Well she was running the entire time I had it on the inverter, with the alternator unhooked the voltage is a little less than 25V most of the time. I thought it should be around 28V unhooked, or else she's bad.

 

[doghead]

To test if you are charging, simply measure the combined battery voltage(24v) with your VOM, then start and run the engine. If your battery voltage reading increases, then you are charging. If it does not, then you are not.

You may damage your alternator by running the engine without it properly connected to the batteries.

Is your inverter a 24V input or 12?

 

[FMJ]

Where you running the inverter off of one battery?

 

[dk8019]

FMJ,

No, it's a 24V inverter, so it feed directly off the battery side, through a disconnect switch, and then to the inverter and is then grounded to the frame.

 

[FMJ]

Well, then your assumption is most likely correct, likely the generator quit.

 

[bgekky3]

When you hook up and inverter or something with a high draw, it is important to hook directly to the batteries. Steel is a conductor but lacks the extra valence electron that copper has. I don't think it killed your generator, but it will make the inverter run better.

 

[dk8019]

Bgekky,

I've done a few large amp installations, say 1000-1200 watt range, and I can't say we ever once ran it back to the battery. The starter, and other high draw devices in the deuce don't have a return on the ground, so I never thought they were necessary.

 

[bottleworks]

Unhook your batts, and check the output of the Gen with a meter, (engine running) you should see 25 volts or so depending on where the regulator is set...

No, no. Never do that. That is the best way to damage an alternator.


Correct charging voltage should be ~28 Volts. You need to confirm that there is power @ the 14 ga wire corrected between the alternator and accessory switch. The alternator will not produce a charge without power there. It will regulate the output voltage based on what it reads at the connection. Check to see if the field has voltage, the regulator may have failed. You can full field the alternator to confirm it's a regulator problem. The regulators, brushes and brush holders are available new for these alternators. Perhaps more... However, you may find it cheaper to buy a used unit. Keep in mind -- It's a used unit.

 

[bgekky3]

I am detailed to the electronics department at work. We have camera trucks with up to 7 12 volt batteries. Chevys, Fords, and Dodges, all charging all batteries off of the 12 volt single or duel factory alts. The cameras run 12v DC, 24v DC, or 110 AC depending on model. Whenever we run a high draw system and don't have a good ground, the truck comes back with a problem. There is more resistance through a body ground than through a copper ground. I run my lights on my personal vehicle and starter through the body ground. My winch and inverter are run through a copper ground. Other than the lower resistance of copper than steel, I can't give you a reason. I don't have any experience with big amps just my .02.

 

[ARMYMAN30YearsPlus]

I think my duece alternator is on it's way out it has to run high RPM to get into the green. I know my alternator on the M818 is bad and it is getting me thinking I need to look into highly reliable commerical updated ones that crank out more current for a big rig. I like original but like LED lights I am not out of the fix it with technology frame of reference

 

[dk8019]

David,

Are there any commercial bolt on alternatives out there? If it will get above freezing here I'll check the output on the wire as mentioned. I think I'm going to fuse the inverter at 60A to hopefully prevent this.

 

[gimpyrobb]

DK, I got a 100amp single wire 24v alt for under $200. When looking at your charging system, keep in mind that there should be a screw to adjust the output of the Generator.

 

[FMJ]

No, no. Never do that. That is the best way to damage an alternator.

So, when I start my trucks with a slave cable and no batteries installed I'll ruin my Generator???? Hasn't happened yet.

 

[doghead]

So, when I start my trucks with a slave cable and no batteries installed I'll ruin my Generator???? Hasn't happened yet.

In this case, if you disconnected the slave cable and let it run with no batteries connected to the truck, it most likely would ruin the alternator. The alternator will sense low(no) voltage and increase it's output until it burns out the voltage regulating components(internal). You will also blow your lights if they are on!

If you have a generator with an external regulator, this usually is not a problem.

If you have not burned something out yet, you have been lucky!

 

[FMJ]

In this case, if you disconnected the slave cable and let it run with no batteries connected to the truck, it most likely would ruin the alternator. The alternator will sense low(no) voltage and increase it's output until it burns out the voltage regulating components(internal). You will also blow your lights if they are on!

If you have a generator with an external regulator, this usually is not a problem.

If you have not burned something out yet, you have been lucky!

Hmmm, thanks. I need to do a test when I get home from work today...

 

[dk8019]

Gimpy,

Mind sharing PNs? I would love to have a higher output unit. What was the difficulty in mounting it?

 

[gimpyrobb]

DK, I got it for my M725. It went in really easy. I might get another and put it on the deuce, but don't know if it would be hard or not. I doubt it would be hard. I will look tonight and let you know what I find.

 

[doghead]

FMJ, what about the test? I hope you didn't explode or something. Please update us.