Bad Alternator???

[RyRy]

Hi,

How do you test if your alternator is working? I think mine might be stuffed on my 78 BJ40.

Theres 2 plugs on the alternator ; one has 2 connections on it, the other has one. If i unplug both with the car running and put the multimeter on the plug with one connection, it only registers around 1 volt! However if i test it when its plugged in, it registers around 12 volts. Seems like my alternator's only putting out one volt!

Also if i put the multimeter on my battery it registers only 12 volts when the car's runnning.

Would this be my alternator or an electrical short somewhere?

Thanks guys

Ryan

 

[Waggoner5]

With a meter across the battery posts, when the engine is running, you should see more than 12 volts. Most 12v alternaters are voltage regulated at 13.8 volts, but under weak battery conditions, you could see lower voltages. Pull the large wire off the back of the alternater and check the output at idle. It should read somewhere between 12.5-13.8volts.
The only way to check it correctly though is to load test it. Most auto parts houses have a hand held tester.
Gary

 

[The Dude]

I think you're in trouble....

My BJ40 is 24V

Yup, take it out and go to the local altenator/starter shop. They should be able to test it no prob.

 

[Waggoner5]

My 61 is too, I guess I should have asked what system he has. Oh well most of it still applies except the voltages???......

 

[Radd Cruisers]

I think the voltage should be around 25 to 28ish.

Usually a alternator will pack it in slowly and is hard to notice.

What is causing you to think your alternator is shot?

Rob

 

[beanz2]

I think Ryan is an Aussie (from the way he describes his alternator as "stuffed" ) Aussie Landcruisers have 12V systems, so his should only read up to 13.8V

Dave

 

[arutgers]

If i unplug both with the car running and put the multimeter on the plug with one connection, it only registers around 1 volt! However if i test it when its plugged in, it registers around 12 volts. Seems like my alternator's only putting out one volt!

Also if i put the multimeter on my battery it registers only 12 volts when the car's runnning.

Ryan, assuming your battery is OK, it's either the alternator or the voltage regulator. The fact that you measure only 1 Volt when the connetors are loose, doesn't mean the alternator doesn't work. That's because the field-coil of the alternator needs battery-power before it delivers volts & amps (and you disconnected the field-coil also by unplugging teh connector).
If you have an external voltage regulator (at the firewall on the driverside; don't know if that is true on RHD), you can check the alternator by overruling the volt regulator. There is a connector near the volt regulator. It should have 3 wires. Pull the connector and make a shortcut between the black & yellow and the white & green wire. Leave the white & black wire open. By doing this the field-coil in the alt will have maximum power. If you start the engine the alternator should give maximum output. You can check this by watching the ammeter at the dash; it should give a firm positive reading. If you have modified or bypassed the ammeter, you can also check by measuring the voltage at the battery; it should be about 13.8 V (or 27,6 V in a 24 v system). If this is the case, the volt regulator is shot and you should replace it. If the ammeter is still at zero or the battery voltage is still 12 V, then it's the alternator. Assuming the alt is mechanically OK, first thing to check are the carbon brushes. They are the most probable cause for failure; replacing them yourselve will cost you about 10 AUS$. Here's a webpage which descirbes replacement of brushes http://www.bitwalla.com/cruisers/articles/alternator.html
Hope this helps.

Ton

 

[RyRy]

sorry mate, yeah im an aussie, so 12v i guess. I'll take it to the auto sparky tomorrow and get them to test it. Checked out the website on changing brushes; doesnt look too hard! Thanks again fellas!

 

[RyRy]

Hey guys,

I took the alternator to an auto electrician and he tested it, and said the brushes need replacing. But he said it would be cheaper for me to get a second hand alternator, as its quite a big job to replace the brushes on these alternator's. I had a bit of a look at it when i got home... Took the big bolt off the front where the pulley is but it still doesnt come off. Took the bolts that hold the oil pump on and that doesnt come off. The 3 screws that hold the back cover bit on wont budge at all. Any tips on how i can do this??

Or alternatively, are there any similar alternators off a different car in australia i might be able to put on my bj40? There isnt too many bj40's here and im sure finding an alternator off one will be veryyyyyyyyyy hard!

Thanks

Ryan

 

[beanz2]

They tend to be the same for a BJ40, B-engined Dyna trucks or Coaster buses of similar vintages. Just bring the alt to the wrecking yard and compare mounting points, vacuum pump attachments, amperage, and connections.

Dave

 

[roscoFJ73]

Ryan You have to separate it by tapping with a soft hammer.
Check the online manual at birfield.com or try another auto electrician.
It doesnt look any harder than any other alternator.

 

[cruiser_guy]

On my BJ60 which is also 12v but an '82 model, you do not even need to remove the altenator to change out brushes. There is a sheet metal cover on top of the altenator that covers the brushes. Pull off the cover (couple of screws) and the brush holder (couple more screws) and you should see the brushes come out with the holder.
Like I say, it may be different with the '78 model.