24v alternator problems

[maat]

Guys, My hj61 24v is having trouble when i have my stereo, head lights and spot lights on, have done all the tests with a multimeter on batteries and alternator itself, this is what i have:

*Under no load and engine off batteries both read 12~v
*Engine running at idle, no acc on both read about 13~14v approx 27~28v when tested from main + to earth
*Engine running at idle, no acc on the alternator pumps out 27~28v
*Turn on stereo (just an mp3 deck nothing huge) and high beams with 2 spot lights and at idle alternator drops to 22~23v and lights etc are dim as faaark! Volt meter in cab reads ~22v
*idle is set at roughly 800rpm and voltage only slightly (2~3v) picks up but still dull lights etc when hand throte is pulled for it to sit on about 1500-1800rpm

I have made a large battery guage cable that goes from the 24v positive terminal to the + point on the alternator but no Improvement.

I guess my question is, Is my alternator stuffed? I read heaps of threads i found when i searched and someone was saying an isuzu 24v alternator with a vac pump attached to it can be fitted to a 12ht pretty easily. Anyone know about this? Whats the go with vac pumps, do they all have different ratings etc? Or can i use any alternator that fits and has a vac pump on it?

Am i looking in the wrong direction with replacing it? Should i just take it to an auto sparky to rebuild and beef up with more Amperage?

Or should i just wack on a smaller pulley?

Thing is doing my head in, im going on a trip soon (few 1000kms) and will definately need my spot lights working etc at hwy cruising speed its not too bad but when 4wd-ing slowly its rediculous..

Thanks in advance guys

 

[Tim-HJ61]

I think you're just exceeding the capacity of your alternator.

What are the wattages of your lights and spotlights? I think the standard alternator is rated at 35A, and they are easy to overload.

Have you checked the brushes, may be a simple thing.

It was years ago now, but some part of mine, the bit that creates the amps, was replaced by the same interchangeable part from a 12v unit that was rated at 60A. Now mine is rated at 24v and 60A. Quite satisfactory!

Tim

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[maat]

So your saying my best bet is to ge the standard alternator re-bushed, and change the amp parts? Did you have the same problem? Im sure my head lights are stock as they arent exactly the brightest. I will have to check..

Anyone else with the same problem?

 

[bj40green]

From what you're saying there is nothing wrong with your system. But.... at idle the alternator is only putting out a few amps to keep your batteries topped off. Call it trickle charge.
So when you switch on your lights you're drawing from the batteries and not from the alternator. The voltage drops to 22V (11V per battery) which is normal behaviour.
If you want more power at idle you have to "fool" the set up by using a smaller pully. With a smaller pully the alternator makes more rpm's and thus putting out more amps to feed your lights.

Hope this helps understanding the charge circuit.

Rudi

 

[maat]

Thanks for the rply rudi, im worried putting a smaller pulley on it still wont fix the problem as i need to really increase my engine rpm to see any different, i suppose thay is a cheap option and i should try it before i start out layimg cash!

 

[BreckenridgeCruiser]

I'm wondering what happens when you try this with the truck off... If it is the same, couldn't your batteries be going? Your batteries should be able to put out enough juice to run all of these at full.

 

[maat]

The alternator shouldnt drop down to below 24volts whilst these acc are running, does anyone know where i can pick up a smaller diameter pulley for my alternator?

 

[roscoFJ73]

What do you have it idling at?

You can buy a brand new OEX for $350 approx and be done with it. Half the rebuilds work,the other half are still are still being fiddled with 6 months later.

 

[maat]

thanks rosco, idle is set at approx 800-850 i would rather buy new if it came to that, Any link to the OEX brand suited to my model? I searched on their site but nothing came up for 12ht

 

[roscoFJ73]

thanks rosco, idle is set at approx 800-850 i would rather buy new if it came to that, Any link to the OEX brand suited to my model? I searched on their site but nothing came up for 12ht

Repco and Ashdown Ingrams both sell them,same company now but get a price off each.There are other brands on ebay also. One seller said the list price from his importer for the 24v was the same as the 12v for both B and H diesel alts.
So there is no reason to pay more for 24v and any ebay seller who sells 12v can get the 24v
I got a really cheap price on a OEX 1HZ alternator from some auto electrical company on Abernethy ave in Belmont,not far from Gt East Hwy,cant remember the name.

 

[maat]

Thanks mate, i will look into it

 

[maat]

If anyone knows of a place making or selling smaller diameter pullies or ones from another vehicle that will fit please let me know!!

 

[roscoFJ73]

If anyone knows of a place making or selling smaller diameter pullies or ones from another vehicle that will fit please let me know!!

They might have something here. You would have to know the internal diameter of your pulley.

Engine Pulleys

Some of the preformance shops might have similar items or know where to go in WA

 

[HJ61 12HT]

I wouldn't go changing the pulley, you will probably introduce more problems, the belt will slip if it has not enough pulley to drive on, you might need a non standard belt etc, and it probably won't make much difference once you are above 1500 revs...

First step should be to replace the alternator brushes, its an easy half hour job.

Then, if you really want to know whats going on, hook up an ammeter temporarily and go for a drive to see how much electric stuff you can run and still keep charging...

My 61 at 1500rpm with the fan on high, window wipers, headlights and stereo on still charges the batteries a little.
(It couldn't keep up before I changed the Alternator brushes)

 

[maat]

I rang a few auto sparkys today to suss out pulleys etc and as soon as i mention 24v import they all turn into cokheads saying theres nothing i can do and that i will need a custom set up for a new alternator etc. Im going to pull it out myself on my time off and put a smaller pulley on it, re bush it and report back

 

[Tim-HJ61]

I rang a few auto sparkys today to suss out pulleys etc and as soon as i mention 24v import they all turn into cokheads saying theres nothing i can do and that i will need a custom set up for a new alternator etc. Im going to pull it out myself on my time off and put a smaller pulley on it, re bush it and report back

Don't you mean re-brush it?

Drive in Electrics in Malaga did mine up years ago. They repair trucks so aren't scared of 24v stuff.

Tim

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