Alternator or not?

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Pat

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It seems my D40's alternator is giving up - the warning light and battery symbol both come on after starting then go away after a few minutes as long as I turn off everything electrical. Putting the lights/aircon, etc on makes the warning lights come back on. The battery is still getting some sort of charge, so I think the alternator is putting out some current but clearly can't handle a load. No error codes being generated.

My first thought was the alternator clutch pulley, but its quiet and smooth and only goes one direction so assuming it was the alternator itself I fitted a complete second hand one from a wrecker.

The problem is still there dammit.

Sooo, it's possible the second hand alternator and/or clutch is also faulty but is there anything else that might be causing these symptoms?

Cheers
 

Old.Tony

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Dirty electricals could. Also, a failing main battery could easily cause problems. Check the main fusible link too, mine went high-resistance and a touch of a soldering iron on both sides fixed it up (I might have burned through some oxidisation, not sure, but it worked and hasn't failed since).

While it's unlikely that two alternators would have the same failure, it's not impossible. If you're happy that the starter battery functions well (get an auto electrician to perform a load test on it, takes just a couple of minutes) and that both battery terminals plus the other ends of the main cables are clean (engine block and alternator) then measure the engine-idling voltage (with all lights and accessories including dual battery chargers, inverters etc turned off) on the alternator and on the battery. They should be very close and should be somewhere between 14.1 and 14.7V.

If there's a difference over about 0.2V between the two, there's a cable/connectivity problem. Re-clean the connections and try again. If it's still varying too much, try putting a 750A jumper cable (RED ONLY) between the alternator and the battery (positive terminal on each, of course). Measure the voltage again. If that's fixed it, your cable from the alternator to the battery is cactus - I've only ever seen this once before.

If there's no major difference in voltage, but it's below 14.1V at the alternator, it's possible that it's not regulating or rectifying properly. This is all internal to the alternator, so changing the alternator (providing that the other alternator is good!) should fix it. It could fail to fix it if the electrical connections are dirty, and the common one here is the ground cable from the battery to the engine block on the engine itself, which seems to corrode and cause issues. I'd try that before chucking another alternator at it. The best test here is to connect the BLACK lead of a 750A starter cable to the casing of the alternator and the other end to the negative battery terminal and measure again. If this fixes the problem then it's definitely a dirty or faulty cable.

So there's a couple of free things to try. If you don't have a 750A jumper cable, ask someone with a V8 or diesel engine if they've got one (technically V8s don't need it, they only draw about 330 amps to start, but our 4-cyl diesels draw about 550A).

Let us know how you go!
 

Pat

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Thanks for the comprehensive reply Tony - your knowledge of D40's is astounding!

I'll give it a go over the next few days and post an update.

Cheers
 

Scott52

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It seems my D40's alternator is giving up - the warning light and battery symbol both come on after starting then go away after a few minutes as long as I turn off everything electrical. Putting the lights/aircon, etc on makes the warning lights come back on. The battery is still getting some sort of charge, so I think the alternator is putting out some current but clearly can't handle a load. No error codes being generated.

My first thought was the alternator clutch pulley, but its quiet and smooth and only goes one direction so assuming it was the alternator itself I fitted a complete second hand one from a wrecker.

The problem is still there dammit.

Sooo, it's possible the second hand alternator and/or clutch is also faulty but is there anything else that might be causing these symptoms?

Cheers
Perhaps it's brushes but it would be strange for both alternators to have that problem.

The alternator is simple to dismantle. It maybe worth overhauling one of them as it's not costly.

A couple of weeks ago I pulled mine apart and replaced the bearings, brushes and over run pulley. It was working fine but the front bearing felt a bit dry. I do a lot of remote expeditions so an alternator overhaul was good preventative maintenance.

The pulley was $104 (AUD) which included the spline tool to get it off. The bearings were $22 for the two and the brushes were $11. For a total of $137 and a few hours I've got a refurbished alternator with quality NTN bearings. In your case you probably don't need a pulley so for $33 you'll get new bearings and brushes but you'll need the tool to take the pulley off. You can buy that for about $20.

For interest the brushes are 23mm long before the wear limit is reached. My D40 had 160,000km and the brushes I removed had 13mm left. So I'd used 10mm in 160,000km.

The brushes are a standard size 8mm x 5mm cross section. I bought a set of universal OEX brand 8 x 5 that were 27mm long and filed 4mm off the ends. I bought them from Napa Auto Parts. I used the springs and retaining clips from the original brushes. I measured the compressed spring length before cutting the wire on the originals then soldered the clips and springs onto the new brushes.

The dealer wanted $27 per brush ... $54 for the pair.
 
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Pat

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Well whadda ya know... after undoing and cleaning a bunch of connections I have a working charging system again (with the original alternator refitted). None of the connections were obviously bad so I'll never know which one(s) were causing the problem...

Replacement alternator back to the wreckers and a bit of money back in my pocket. No wait, the Nav needs the aircon topped up and an oil leak investigated, damn thing is keeping me poor!

Cheers again for the help
 

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