Alternator help!

Good evening guys hope you are all good.

So my alternator is putting out Volts but no Amps

I there anything i should be checking or is me alternator scrap?

Cheers Landy Lee

How are you checking it?
How many volts?

lynall said:

How are you checking it?
How many volts?

Click to expand...

Amps with a DC clamp meter and volts 14.4 when running

If it's pumping out a voltage it can provide current (Amps) the two are intrinsically linked.
The question is how many Amps ...
To test this start the engine, disconnect the + lead from the battery and put an ammeter between the cable (+) and the + terminal on the battery.
Most DMM's have a amperage setting/connection.

With the battery disconnected, do the lights work ? (Yes = you have amps)

Why were you checking it?..

landy-lee said:

Amps with a DC clamp meter and volts 14.4 when running

Click to expand...

Well if it is making over 14 V I would ignore the amps and just keep on trucking.

miktdish said:

If it's pumping out a voltage it can provide current (Amps) the two are intrinsically linked.
The question is how many Amps ...
To test this start the engine, disconnect the + lead from the battery and put an ammeter between the cable (+) and the + terminal on the battery.
Most DMM's have a amperage setting/connection.

With the battery disconnected, do the lights work ? (Yes = you have amps)

Click to expand...

This is your answer mate. The amps will depend on what's drawing power. if any of the electrics work then you're fine

As above, the amps registered depends on what is used and a good condition charged up battery will draw little.

Hi guys thanks for the help.

ok so i do have amps but it is inconsistent. i have put a clamp meter on the heavy brown cable on the back of the alternator and im getting between 3 and 11 amps.

when i increase the engine revs i goes up by maybe 2 amps.

@miktdish i have done as you said and the lights do come on but i guess that is because i am making just enough amps to light em up?

Cheers Landy Lee

Then, Mr Lee, you are producing current, so no need to worry ...
You need to 'draw' the current to be able to measure it. For example if you had a dead short across the alternator it would deliver the max it could, for a short time and then (internally) melt.
If you put a device that needed 80A to operate then your 100A alternator would provide the current (typically altenators are 75 to 80% efficient) as long as you span it fast enough with enough power to overcome the back electro magnetic force (EMF) that was trying to stop it.

So you need a 'load'.
The one to borrow is a "Clore Automotive Solar 1874 500 Amp Carbon Pile Battery Load Tester" or you can buy one ..... from Amazon UK (for some reason I can't post a link)
Here's the scoop ...

landy-lee said:

Hi guys thanks for the help.

ok so i do have amps but it is inconsistent. i have put a clamp meter on the heavy brown cable on the back of the alternator and im getting between 3 and 11 amps.

when i increase the engine revs i goes up by maybe 2 amps.

@miktdish i have done as you said and the lights do come on but i guess that is because i am making just enough amps to light em up?

Cheers Landy Lee

Click to expand...

The amps will increase or decrease depending on the draw from working electrics, which is usually constant. The voltage regulator on the alternator controls voltage not current. I'm not an expert but i imagine the current will increase initially after starting to top up the battery and then will depend on the draw from accessories, lights etc. I suspect a bit of variation is normal.

To be honest if the charging voltage is within the normal range, your battery is healthy (this can be checked by looking at its charge with the car off, do it about an hour after you last switched it off so the surface charge has time to dissipate) and all your electrics work, just forget about it.