I've got an old Ford 800. Battery dead, 5 years old, so I thought it was reasonable. Put in a new battery, started and mowed for a few hours. I shut if off and started it again. Next morning, battery dead. Recharge battery, disconnect alternator since I couldn't find any short anywhere. Started next morning. Seems like the alternator is draining the battery. Is there a way I can test the alternator? Thanks.
Alternator Problem Maybe
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sunnyside360
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Some Advance Auto Parts stores can test alternators. A few years ago they would do it for free -- maybe they still do. Give them a call.
E/S
Gold Member
There is an easier ways;
1 - Start the tractor
2 - Disconnect the positive cable on the battery
3 - Check the voltage at the cable to ground, it should be around 14 volts (you may have to reeve the engine slightly).
The other way is to hold a screwdriver blade next to the alternator / generator shaft at the back side with the engine running. If it is charging there will be a strong magnetic field and the blade will be pulled to the shaft.
Hope that helps.
E/S
1 - Start the tractor
2 - Disconnect the positive cable on the battery
3 - Check the voltage at the cable to ground, it should be around 14 volts (you may have to reeve the engine slightly).
The other way is to hold a screwdriver blade next to the alternator / generator shaft at the back side with the engine running. If it is charging there will be a strong magnetic field and the blade will be pulled to the shaft.
Hope that helps.
E/S
Diamondpilot
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Does it have a alternator? My 861 had a generator until we did a alternator conversion. Is it a 6 volt battery? If so I am guessing its a generator.
Chris
Chris
to check system for drain on battery, disconnect either batt cable with key off, engine off. connect ammeter one lead to batt cable, other lead to respective batt post, it will show amount of drain if present. to check your setup, turn key switch on with ammeter in place, if correctly hooked up you will see meter show the drain. if you have a drain with key off, disconnect alternator, assuming you're using a delco with internal regulator, if drain disappears, you found it. if you are using alt with external regulator, disconnect regulator as well as alternator, one at a time and check. you can also use a test light, hooked up the same way, aligator clip on cable, probe on batt post, in series with batt, if you have a drain bulb will burn. with everything off, test light will be off. to check charging system, NEVER disconnect battery cable with engine running. a charging battery gives off hydrogen gas, even a small spark could cause battery to explode. i have seen two explode, like a stick of dynamite. to check, put volt meter on batt terminals. better to check amperage, but if proper voltage is present, its charging. test light method for drain is more than adequate for your tractor. hope this will be of some help.
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RickB
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Never operate an alternator without it being connected to a battery. Doing so is the best way possible to damage a perfectly good alternator. he same voltasge test should be performed with the battery connected, and withthe tractor both running and not. There should be a voltage difference between the two tests. In this case, we may also have a bad diode set in the alternator which is allowing the alternator to drain the battery at rest. Often an alternator will charge OK with this problem.
Diamondpilot
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Did you guy miss that this should not have a alternator unless converted to 12 volts???? The 800 series Ford tractors had a 6 volt system, positive ground, and a generator, no alternator.
Chris
Chris
banjodunn
Veteran Member
G'day i think you have done your own test, disconnected and no prob if you really want to test hook it back up again and see if it goes flat again i would say you have blown a diode if it is an alternator
Jon
Jon
Volfandt
Veteran Member
Assuming that this tractor has been converted to 12v properly and it's worked as desired for a time, for a good battery to drain down over night, there has to be something thats connected directly to the battery thats finding it's way to ground.
In an alternator there are reverse current diodes installed that are supposed to prevent a batt from dischargeing through the alternator but if they are blown and shorting out, they would be the primary cause IMHO. Alot of conductive material built up on the starter solenoid at where the main hot battery cable connects is another.
It's never good to throw new and sometimes expensive parts at a problem until one has tried to isolate via troubleshooting.
One of the best and easiest ways to troubleshoot a possible battery discharge problem is to make up a simple tester w/an automotive type bulb, I use an 1156 (but any will do), and solder two wires with a bit of length to it. One wire should be soldered to the lead tip and the other to it's case ground. To make sure it's good, just place one wire on the batt + and the other on the batt -, it should glow if it's properly soldered.
Now take the + battery connector off of the battery, leaving the - connected. Wrap one of the testers wires around the batteries positive post and the other wire around the connector you just removed (I use vise grips to keep the wire on the batt post). With the key off, if the bulb glows you've got something thats shorting to frame/battery ground. To determine which device, you can either start removing fuses one at a time or remove the "hot" connector at each device, i.e. starter solenoid, alternator etc., until the lamp goes out.
If the tractor uses a positive ground electrical system, leave the positive connected (ground) and lift off the negative connector (hot).
re. alternators
even with the reverse current diodes they still allow (leak) a very small amount of current through them (milliamps) and a system with a good battery and charging system will keep up with no problem. This cheap lamp tester won't glow in this case because the current isn't sufficient to energize it but, any appreachiable amount of current will glow that bulb. Keep in mind that even if the bulb just barely glows, that signifies too much current is leaking and is a problem.
I like using the bulb over a multimeter because the meter when set to measure millamps will show the normal discharge of the alternator and cause a replacememnt of a properly functioning alternator (BTDT)
Generators generally don't have any leaks because their regulators have a cutout relay that opens the circuit when it's not making electricity.
Good luck
In an alternator there are reverse current diodes installed that are supposed to prevent a batt from dischargeing through the alternator but if they are blown and shorting out, they would be the primary cause IMHO. Alot of conductive material built up on the starter solenoid at where the main hot battery cable connects is another.
It's never good to throw new and sometimes expensive parts at a problem until one has tried to isolate via troubleshooting.
One of the best and easiest ways to troubleshoot a possible battery discharge problem is to make up a simple tester w/an automotive type bulb, I use an 1156 (but any will do), and solder two wires with a bit of length to it. One wire should be soldered to the lead tip and the other to it's case ground. To make sure it's good, just place one wire on the batt + and the other on the batt -, it should glow if it's properly soldered.
Now take the + battery connector off of the battery, leaving the - connected. Wrap one of the testers wires around the batteries positive post and the other wire around the connector you just removed (I use vise grips to keep the wire on the batt post). With the key off, if the bulb glows you've got something thats shorting to frame/battery ground. To determine which device, you can either start removing fuses one at a time or remove the "hot" connector at each device, i.e. starter solenoid, alternator etc., until the lamp goes out.
If the tractor uses a positive ground electrical system, leave the positive connected (ground) and lift off the negative connector (hot).
re. alternators
even with the reverse current diodes they still allow (leak) a very small amount of current through them (milliamps) and a system with a good battery and charging system will keep up with no problem. This cheap lamp tester won't glow in this case because the current isn't sufficient to energize it but, any appreachiable amount of current will glow that bulb. Keep in mind that even if the bulb just barely glows, that signifies too much current is leaking and is a problem.
I like using the bulb over a multimeter because the meter when set to measure millamps will show the normal discharge of the alternator and cause a replacememnt of a properly functioning alternator (BTDT)
Generators generally don't have any leaks because their regulators have a cutout relay that opens the circuit when it's not making electricity.
Good luck
