Alternator/ charging problem

16bore

Not strictly car related, it's to do with a Zetor tractor. Very basic tractor, 16 years old, so nothing too strange about it.

Anyway, battery/alternator light is on all the time on the dash. It used to go out if you revved up a good bit, but now this makes no difference - on all the time. The battery is not getting charged either, we have to jump start every morning. Tractor runs happily all day, but if we turn it off, it has to be jump started again.

The battery is reading 12.1 volts with engine off. With the engine running, battery still reads 12.1 volts. I measured the voltage at the pole of the alternator, that was 12.1 volts too.

Took the alternator off and got it bench tested, they said there was nothing wrong with it. Battery was tested ok as well, am trickle charging it overnight.

What should I check next?

Avns1s

Is the fan belt tensioned correctly?

16bore

Good and tight

Avns1s

OK Can you check for continuity between the positive (large) terminal on the cable at the alternator and the +ve post of the battery. It could be a failed connection or a break on this cable.

Alternatively check the voltage between this terminal and earth. Should be the same as the 12.1v you referred to earlier.

16bore

Will check tomorrow...

Thanks for help

jimmyw

Avns1s wrote: »

OK Can you check for continuity between the positive (large) terminal on the cable at the alternator and the +ve post of the battery. It could be a failed connection or a break on this cable.

Alternatively check the voltage between this terminal and earth. Should be the same as the 12.1v you referred to earlier.

Yeah but 12.1 volts is too small.It should be at least 13 volts for a start.Would it not read the higher volts at the alternator terminal even it there was a break in that cable?

Or maybe the alternator is not getting any/the correct amount "exciting " current through either the warning light, or through whatever means it uses.

Avns1s

jimmyw wrote: »

Yeah but 12.1 volts is too small.It should be at least 13 volts for a start.Would it not read the higher volts at the alternator terminal even it there was a break in that cable?

His battery reading is currently 12.1v. The purpose of that test is just to check that the +ve cable is intact and there is a path back to the battery. The terminal should be disconnected from the alternator when doing it and the engine should not be running.

If a cell was gone in the battery, the red light would still go out with a rev on the engine.

jimmyw

Yeah, but when its running it should be more at the terminal even if the cable was bad.

16bore

That's what has me a little puzzled, I would have thought the voltage at the alternator terminal should be about 13 -14V. When I took that 12.1v reading, the cable was attached to the pole. Can I damage the alternator by running it with no cable attached to the pole?

Cogsy88

Most likely cause is a damaged cable or corroded connections. if the alternator an battery are in good condition The usual reading should be around 14.4v. Disconnect the battery and check continuity of the cables with your multimeter.

jimmyw

16bore wrote: »

That's what has me a little puzzled, I would have thought the voltage at the alternator terminal should be about 13 -14V. When I took that 12.1v reading, the cable was attached to the pole. Can I damage the alternator by running it with no cable attached to the pole?

Yes it can be damaged, don't run the engine without the cable.

Avns1s

I'd still have my doubts about that alternator being faulty.

The charging circuit where an alternator is involved is relatively simple in that there aren't many things to go wrong.

This wouldn't appear to have anything to do with the battery based on the symptoms described.

The link from the ignition switch to the small alternator terminal and the bulb are ok or else the bulb wouldn't light.

That leaves the main cable which you should test the continuity of to rule that out.

After that you're back to the alternator!!

mickdw

Ifs is anything like the earlier 6211, it will have a seperate regulator under the dash. Failed regulator could possibly lead to a failed exciting signal meaning the alternator would never put out the correct voltage of around 14v.
check for a shiny rectangular box with 4 wires connected to it.

jimmyw

Can you really check a large cable with a continuity tester? Maybe the ohm setting on the multimeter would be better.There could be continuity but still not enough to carry the heavy current needed for an alternator.

It might not be "excited" through the warning light too.Some use other ways instead. My guess is maybe the alternator under load? or the exciter current.

Ded_Zebra

I wouldn't rule out a bad battery yet. Charge the battery over night and measure the voltage in the morning. It should be about 12.6V.
Then have someone try to start the engine while you check the voltage. If while cranking the voltage drops to 6-7volts the battery has most lightly had it.

mickdw

Just to add. If you find that the tractor has a regulator, I might have the correct one here. Would be happy to send it to you €25 and take it back if you didn't need it.

16bore

Battery has charged to 12.6V.

Caught up in family stuff today, will be Monday before I get back to the tractor!

martinr5232

Connect a jump lead between the main live coming from the alternator and the positive on the battery that will tell you if there is a problem on that cable or not.

I think though as mick said they have a seperate regulator its a long time since i worked on tractors though but maybe worth following the wires back from the alternator.

16bore

Using a fully bench charged battery today - 12.6V

There is continuity on the cable between alternator and battery, so don't think that can be the problem. Ran a jump lead from + pole on alternator to + pole on battery, still only getting 12.4 V.

Disconnected the battery charging/warning light wire on the alternator, there is 12 V on that wire. Light goes out, and comes on again when I earth it. So that seems to be working ok.

Didn't see a regulator under the dash, but it's pretty cramped and hard to see. It's a bit awkward trying to trace the wires, but I'm trying to check all connections and terminals for corrosion and good connections.

Any more ideas? Otherwise it's going to the garage!

Thanks for all the suggestions anyway

Avns1s

Post a picture of the alternator, someone might know if the "regulator" is internal or external. I'd be surprised if its not internal unless the alternator is 40 years old and even then.......!

If it's not the external regulator, then your alternator is the problem.

mickdw

Avns1s wrote: »

Post a picture of the alternator, someone might know if the "regulator" is internal or external. I'd be surprised if its not internal unless the alternator is 40 years old and even then.......!

If it's not the external regulator, then your alternator is the problem.

Well we have an 1989 zetor here with external regulator.



Here is what the regulator under the dash looks like in our tractor. Yours may or may not have one

16bore

Not a great photo, but is that silvery rectangular thing the regulator?

It's a 1996 Zetor 6340

jimmyw

First I assume that you only have two wires going into the back of the alternator OP.The problem can really be only 4 things in my opinion.First, the "exciting" (in your case the warning light circuit) current is not going into the alternator.Two, the alternator is not producing current to the battery.Three, a bad earth on the alternator (less likely).Four, bad wire to the batt.

If when you have the engine running, if there is at least 13 volts on your test meter at the alternator post, then the problem could be the wire from the alternator to the battery.

But if there is only 12 or there abouts there, then the alternator is not producing current, its as simple as that.Now since your test on the warning light appears to be ok, then I think that can be ruled out.Which leaves the earth.You could use a jumper cable from the body of the alternator to the engine to rule that out aswell.


In my opinion, despite what your alternator repair facility says, I would say its an alternator fault, but only if there is just 12 volts at the alternator post.

16bore

Success at last.

Bad connection between warning light (exciter?) and alternator, where it clips on to the alternator. Gave everything a rub with sandpaper and a wire brush. Even though the warning light circuit was testing ok, wasn't making a connection with alternator. Was beginning to tear my hair out over this.

jimmyw

16bore wrote: »

Success at last.

Bad connection between warning light (exciter?) and alternator, where it clips on to the alternator. Gave everything a rub with sandpaper and a wire brush. Even though the warning light circuit was testing ok, wasn't making a connection with alternator. Was beginning to tear my hair out over this.

Its nearly always the small simple things that trips ya up. :(Ya got it going anyway.Light now goes off?

itsirishfarmer

put distilled water in all the cells ,there might be 6-8 on a battery

16bore

Yes, light goes off. 14.8 V at alternator and battery.
At least I will know what and how to check next time.

I topped up the battery cells when I bench charged it.

Thanks.