General ALternator question

[shinnlinger]

HI,

This alternator is on a LUll telehandler, but it is not working. I took a meter and can't seem to get much out of it when it is running , but where would I check?

I assume it would give me 14+ volts between the bottom bolt obviously grounded and one of the top two, but no go.

Any suggestions?

Thanks.

 

[Coyote machine]

Not familiar with the telehandler but I would check the volts at the battery with the engine off and then running and then with a load like headlights on to see if you get any different readings at the battery.
Looks like it has a built in voltage regulator, (black box). Can you remove it and have it tested by a rebuild shop?
What were/are the symptoms that make you suspect it is bad?

Could be bad regulator, alternator brushes, diodes, winding- hard to say without more info.

 

[shinnlinger]

HI,

There is nothing on the Lull (big construction forklift) to put an electrical load on the machine except the fuel pump and starting it and it doesn't need the fuel pump. There are some wires that are disconnected so I was just trying to see if the alternator was good by seeing if it put out any juice.

 

[DieselPower]

From the looks of it the bottom right stud that has a wire going to the mounting bolt is going to be the ground. The center stud looks like it has a heavy gauge wire going to it and is probably the output terminal. The top stud may be a accessory tap for something like a tachometer or may be a external sense/excite wire. With the engine off check the voltage at the + output terminal. Start the engine and it should increase to around 13.5 volts.

Are you having starting problems? Like Coyote machine just wondering what the problem is. If it has been setting for a extremely long time without running it is possible that the rotor has lost it's residual magnetic charge and needs to be remagnitized. Does the voltage increase at all when the engine is started?

 

[schmism]

HI,
I took a meter and can't seem to get much out of it when it is running , but where would I check?

with out knowing the specifics of it i cant say for sure.

but most 2 wire alternators (which it looks like it is) require a second 12v source to engergize the feild before it will start generating current. with out that source it will seem as if the alternator is bad (not produceing any voltage)

if you know the connections are good (good 12v on feild wire) then the second most common failure is the rectifier (the thing that takes the AC current and turns it into DC current)

 

[banjodunn]

G'day as said earlier i think you need another wire going into the back prob a blade push on terminal it should be running through a light on the dash and if you have got a wire like that near the alt put a test light on it and it should power up with the ign on. Hope this helps


Jon

 

[some zilch]

usually, an oil pressure switch will tell the alternator to turn on, giving it the 12v needed to make 14v

 

[wvpolekat]

usually, an oil pressure switch will tell the alternator to turn on, giving it the 12v needed to make 14v

Interesting. I can't say that I can ever recall a setup like this. All the ones I have seen run it through the idiot light circuit.

 

[shinnlinger]

THanks folks,

Too wet to play outside today, but there are some disconnected small wires. I will see if any of those wires power up with the key or if they are always hot. Now where would I connect one of these wires to the alternator? I don't believe this machine has any lights on the dash, but I have an idea of where to start.

Thanks again.

 

[banjodunn]

G'day a little bit hard to tell from your pic but look in the back of the alt between the two term with the wires on them and look for a male blade term looking at you


Jon