31 replies to this topic

[Rockoz]

Once the initial excitation is done, the alternator pretty much takes care of itself through a third set of diodes that handle the rotor power.

You can get an alternator working by 'flashing' it.

It needs external excitation so that it doesnt drain the battery when it isnt running.

Electronic trickery. lol

 

The indicator lamp works the following way.

When the alternator isnt producing power, the indicator terminal is effectively at 0v.

With 12v from the ignition to one side of the lamp and 0v on the alternator side, the lamp glows.

Once excitation has taken place, the indicator terminal goes to output voltage.

Once that happens you have output voltage on both sides of the lamp, so no current or illumination.

Im guessing depending on the internals of the regulator, there needs to be a reasonable current flow to cause excitation.

It is likely to vary according to manufacturer, but would all be around the same ballpark figure.

But from memory somewhere between 1/2 and 1 amp, given the indicator lamp is probably around 5 to 10 watt.

Would have to do some searching to get better figures.

But a fairly low resistance is needed to get excitation started.

Certainly not in the 100s of ohms generally.

 

I have flashed the indicator terminal on alternators to get them running.

All that is is touching 12v direct to the terminal for a brief moment.

Once running, a keen ear will be able to hear the alternator producing power.

Once you know what to listen for, it is easy to detect.

 

Cheers

 

Rob

[Dr Terry]

Once that happens you have output voltage on both sides of the lamp, so no current or illumination.

Im guessing depending on the internals of the regulator, there needs to be a reasonable current flow to cause excitation.

It is likely to vary according to manufacturer, but would all be around the same ballpark figure.

But from memory somewhere between 1/2 and 1 amp, given the indicator lamp is probably around 5 to 10 watt.

Would have to do some searching to get better figures.

 

Cheers

 

Rob

Most cars of the 60s,70s & 80s had a 5W or 6W alternator warning light globe.

 

That's close enough to 1/2 amp for me.

 

I remember I had a car in once which had intermittent alternator charging issues, which all boiled down to the owner fitting a little 3W globe into that stop. Fitted a 6W globe, job done !

 

Dr Terry

[minor miss steak]

So it certainly sounds like the adapter plug they sent was incorrectly wired and that is what I thought when I tested it. If what I'm hearing is that the alt light is between 10 and 20 ohms and the current is therefore around 2/3 of an amp (0.6666 amps) I should have no prob now. Great work guys.

 

Last thing, could someone post a link to somewhere that stocks the fusable link, I can't seem to find one.

[Rockoz]

To be honest I dont think you will find an original fusible link.

 

But a good supplier for something aftermarket would be JAS Oceania.

 

Because the standard fusible link is in a hostile environment, I would consider a slight rewire and get it away from the starter.

Run it from the battery instead and fit a modern fusible link.

 

Got quite a few people out of trouble many years ago when the original fusible link blew.

Sometimes they will actually pop without showing any external signs.

A quick tug on the link shows it has blown. Twisted the ends together to get them moving temporarily.

 

Fuses in any form are a real compromise for circuit protection.

The fuse wire by design is a lot smaller diameter than the wire it protects.

As such it is prone to heating up a lot more than the wire itself.

As it heats up, it oxidises slightly.

That oxidisation reduces its CSA ever so slightly.

So the next time it heats up just a bit more and oxidises some more.

Over time the CSA keeps reducing to the point where it wont support even a low current flow.

At that point, they just pop instead of blow.

 

Made lots of money over the years particularly at the start of winter.

Would get a call to a house which had lost power.

Quite often I was already in the pub relaxing.

Asked them to check the fuses.

They invariably said that they had done that and that none were blown.

Turn up and check the fuses.

They look good, but when you pull on the ends the wire is no longer intact.

Quick replacement and collect the after hours call out fee.

Usually with a lot of animosity, as I had "just changed the fuse wire"

 

Anyways. I digress a little.

 

Cheers

 

Rob

[Rockoz]

Just a thought on the alternator.

 

Apparently there is a difference between a charge light activated alternator and one that is regulated by the computer.

LS alternators I believe are like that and can be difficult to get running.

Just something I remember reading from somewhere a while back

 

Cheers

 

Rob

[minor miss steak]

So, after all this time I finally have the whole system up and running. Voltage across the battery with the engine running at idle is 14.66 volts which I hope is not to much , any thoughts anyone?

 

To conclude all this I was trying to reuse as much off the original wiring harness as possible and tried just completely disconnecting the regulator and connecting the indicator ( gen light) on the original alternator connection plug to the approriate anternator connection. THIS DID NOT WORK.

At the regulator there are two plugs, one is a T shaped double connector and the other a single plug. I had to run a new wire from the regulator single plug to the alternator in order to get the gen light to work.

 

Since I wanted to run the voltage sensing wire from the "end of the system" I also ran a new connection from the power wire on the electric fan thermostat to the alternator voltage sensing connection and the only original alternator wire I could use was the fuse box to alternator positive wire, of course I also had to run an additional "battery cable" to from the alternator to the battery positive and I had to replace the original battery negative to car body connector with another battery cable since the original wire was quite thin and only designed to handle around 70 amps max and the new alternator can put out up to 250 amps if needed.

[Rockoz]

14.66 should be okay.

My VF SS often indicates 15.2 and the auto eleco said that should be fine.

Only went to him because the battery wouldnt charge and it was under warranty.

 

Optimal for auto stuff is 13.8.

But a bit higher isnt an issue.

 

Cheers

 

Rob