TC-18 Alternator Check

[Riddler]

When I use a 12v sprayer on my TC-18, the battery drains after awhile (e.g., after an hour or two) even when I maintain an engine speed of 1,500 to 2,000, or more. The sprayer pump is a 2 gpm, 60 psi, model, that is supposed to draw 7 amps. The wires to the spayer are attached to the tractor's battery terminals with alligator clips. After I disconnect the sprayer and charge up the battery, the tractor starts up and seemingly operates fine for other uses. Because the battery takes (and seemingly holds) a charge, I have been assuming that my problem isn't a bad battery.

The battery terminal connectors aren't in the best shape, so I'll start by changing those. While I do that, is there a way I can use a garden variety volt/amp/ohm meter to check whether the alternator and/or voltage regulator may be malfunctioning?

Also, any tricks on how to prevent future corrosion of the battery terminal connectors would be much appreciated.

 

[jinman]

If you measure the voltage on a good battery with the engine not running, it should be anywhere from 12.5 to a little over 13 volts depending on how long it has been since the engine was running. With the engine running, you should measure around 14.2 volts. If you have less than 13.85 volts at the terminals while you are running the sprayer, then your alternator is probably not carrying the load.

A 7-amp sprayer really doesn't pull that much more than your headlights would. If you run your tractor with just the headlights on, is the battery depleted? I would measure your alternator for 14+ volts out with the headlights on and also check the specific gravity in each cell of your battery to see if something isn't up. If your battery terminals are dirty and you have alligator clips on the terminals, you should be pulling current exclusively from your alternator. There's a chance that your alternator's power lead is loose or corroded at the alternator, but the symptoms you describe don't sound like dirty battery terminals to me. I don't think clean terminals will improve your situation although you ALWAYS want to have clean terminals for the best battery charging.

 

[Riddler]

Thanks Jim. I agree that the sprayer pump ought to be working off the alternator exclusively. Because the pump runs the battery down relatively fast, I have been suspecting the alternator. I almost never use the headlights, so I've never had the opportunity to observe whether the battery runs down with the lights on and the tractor running.

What's confusing is that once I've recharged the battery with the charger, the battery and alternator combine to work the starter motor well enough. Then again, the draw on the battery at starting is a short, one shot deal, so perhaps the alternator functions just well enough to restore battery function (for starting purposes) between the occasional starts.

I can't get to the tractor until this weekend, but when I do, I hope the voltage test reveals something. I use the sprayer to control weeds in vine rows, and at their rate of growth this time of year, time is not on my side!!

 

[jinman]

If you run a long set of test leads from a voltmeter up to the battery with the voltmeter set on the 20 VDC full-scale range, you will be able to operate your tractor and monitor what the charging voltage is doing while you operate the sprayer. When you turn your sprayer on, the normal operation of your alternator and battery would hardly show on the voltmeter. If you can see the volts going down steadily as you spray, it's a sure sign that your alternator isn't doing its job.

I don't know what the rated capacity is on your TC18's alternator. I would expect it to be at least 25 amps. Mine on my TC45 is 45 amps and there is a 40 amp main fuse for protection. If you check your main fuse and add about 5 amps, that's probably the maximum load of your alternator. It would be a really wimpy alternator to not be able to keep the battery charged with a 7 amp load.

Since you are using alligator clips to power your sprayer, are you sure it is not faulty and pulling too much current? Does it have an inline fuse? I would expect it to have at least a 10 amp inline fuse if it normally pulls 7 amps maximum. If it has no fuse, running with alligator clips is really taking a chance in case something shorts out.

BTW: The little red and green felt washers really do help to eliminate corrosion. Also, there are corrosion preventing sprays that work well. I have one that sprays a yellow foam and turns pink as it treats corrosion and prevents it in the future. Either or both should solve your problem.

 

[Riddler]

I'll report back when I do the voltage test.

I've never liked clipping the pump leads to the battery terminals. For that reason, just this past weekend I installed a switch box and switch on the fender next to the driver seat (i.e., next to the other controls), and an extension cord type female plug at the very rear of the tractor. Next, I'll make a permanent connection to the battery terminals (probably with lugs of some type) and run permanent wiring from there to the switch box. I will complete the retrofit by attaching a regular male plug to the pump leads. Then, when I use the sprayer (which is 3pt mounted), all I have to do is plug it in at the back of the tractor. The switch will allow me to turn the pump on and off easily from the driver seat. I never thought of including a fuse somewhere in the new permanent wiring, but now I will. Thanks, jr

 

[Riddler]

Well, installing a new set of (fancy brass) battery cable connectors, and adding some lugs to securely connect the pump feed wires to the battery, appear to have done the trick. With the pump off, the voltage at the battery after starting the tractor reads 15 volts (at approximately 1,500 rpm). With the pump on, it only drops to 14 volts. I am assuming that with those readings, there must be nothing wrong with the generator.

Just FYI, the OEM battery cable connectors on that tractor were made of relatively thin, stamped metal. It didn't take much corrosion to weaken them to the point where they wouldn't hold the battery terminals firmly. All I can figure is that the old terminals might have been loose enough to cause an intermittent connection between the alternator and the battery, while at the same time still allowing the pump to draw enough current from the battery to run it down.

Oh well, with the crisis solved, I can live with the mystery . . .

 

[jinman]

Riddler, I used to work with a guy in the US Navy who said, "It's a grape!" to describe any easy task. I guess that was his version of "piece-o-cake!" Anyhow, as you're a vinyard owner, I thought that expression was appropriate.

I checked my Repair Manual for my tractor and it said the charging voltage should be 14.5 to 15.0 volts. It should never exceed 15.5 vdc. So, it sounds like you have an alternator working within spec. If the battery is failing, I'd bet the battery is at fault.

Nice job!