Alternator woes - The saga continues - SOLVED

[Flynndog]

I should clarify that when I start the car the alternator O/P is 12V. Is that correct? I thought it was supposed to be ~13V even at idle. Once I touch the accelerator it comes on and stays on at 13-14V. That doesn't sound right?

 

[Old.Tony]

I'm highly suspicious of the alternator's pulley, the belt or the brushes, if it needs that many revs to get the voltage up, but it sounds like things aren't too bad.

Typically, alternator output is rectified (because alternators actually produce AC) then regulated to somewhere between 14.4 and 14.7V. You'll see it as 14.1 to 14.4V when you check the running vehicle (because things are running and power is being consumed). It seems that at 1,000rpm yours is working properly - now you need to determine if you've got a loose fan belt, pulley or something.

When you FIRST start the car batt volts should be mid-13s or so but the act of starting (draws about 500A) for (say) 3 seconds actually only uses 0.4Ah so replenishing that at a nominal 20A of output should take the alternator about a minute and a half.

So - if you don't see 14V after two minutes of engine running, something's not quite right. Could be a loose belt or pulley (more commonly the belt, I've only heard of the keyway breaking on the shaft once). It could also be the battery with some internal fault - some sulphation, or cell wall degradation.

Bit concerned about those fuses blowing. Has the harness suffered any impact? What about heat damage? Could the wiring have been subjected to a high enough current to cause the insulation on some of the wires to melt? That would cause unpredictable results, blowing fuses that shouldn't have any problem.

 

[Flynndog]

I'm highly suspicious of the alternator's pulley, the belt or the brushes, if it needs that many revs to get the voltage up, but it sounds like things aren't too bad.

Typically, alternator output is rectified (because alternators actually produce AC) then regulated to somewhere between 14.4 and 14.7V. You'll see it as 14.1 to 14.4V when you check the running vehicle (because things are running and power is being consumed). It seems that at 1,000rpm yours is working properly - now you need to determine if you've got a loose fan belt, pulley or something.

When you FIRST start the car batt volts should be mid-13s or so but the act of starting (draws about 500A) for (say) 3 seconds actually only uses 0.4Ah so replenishing that at a nominal 20A of output should take the alternator about a minute and a half.

So - if you don't see 14V after two minutes of engine running, something's not quite right. Could be a loose belt or pulley (more commonly the belt, I've only heard of the keyway breaking on the shaft once). It could also be the battery with some internal fault - some sulphation, or cell wall degradation.

Bit concerned about those fuses blowing. Has the harness suffered any impact? What about heat damage? Could the wiring have been subjected to a high enough current to cause the insulation on some of the wires to melt? That would cause unpredictable results, blowing fuses that shouldn't have any problem.

Agree with the short or other fault Tony. It started last year,(http://www.navara.asia/showthread.php?t=13393) and I replaced/upgraded the alternator. Obviously that didn't fix the issue as later the light still kept coming on intermittently.

In July of that year, I noticed one day the air conditioner had stopped working at some stage. So they may have been isolated issues or they could be related. In relation to the AC, the 10A fuse will run the AC for about 20 minutes and then the fuse blows. I was thinking the compressor originally, but now I am wondering if it could be a fault either in the harness or the AC circuit.

My next move is to check the AC voltages and the relay

 

[Old.Tony]

Actually while I think about it I'm not sure the 10A fuse in the alternator would be enough, if the alternator is capable of delivering 90A I'd expect the fuse to be a little higher than 10A!

 

[Flynndog]

Actually while I think about it I'm not sure the 10A fuse in the alternator would be enough, if the alternator is capable of delivering 90A I'd expect the fuse to be a little higher than 10A!

15 perhaps

 

[Flynndog]

Anyone know how to remove the relays?

 

[robmacca]

Actually while I think about it I'm not sure the 10A fuse in the alternator would be enough, if the alternator is capable of delivering 90A I'd expect the fuse to be a little higher than 10A!

There should be 2 fuses.... one for charging the battery (80A Fusable Link) and the other one for the charging/warning light, etc on the Dash. this one is 10A.

Not sure if this will help u.....see attached pic

 

[bods]

Usually they just pull straight out.

 

[Dion]

Actually while I think about it I'm not sure the 10A fuse in the alternator would be enough, if the alternator is capable of delivering 90A I'd expect the fuse to be a little higher than 10A!

Tony I believe that 10A fuse supplies excitation current to the alternator, 10A is "ample" (sorry, couldn't resist). So to throw something else into the conversation, Flynn i think you mentioned that the battery light on the dash is sometimes on? Is it on at the same time that you are measuring <12V at the battery & alternator? As the lamp is illuminated by the difference in potential between the battery and the alternator, when the battery is higher the lamp is on. If excitation current does not reach the alternator, it will not generate.

 

[Flynndog]

There should be 2 fuses.... one for charging the battery (80A Fusable Link) and the other one for the charging/warning light, etc on the Dash. this one is 10A.

Not sure if this will help u.....see attached pic

Hi Rob,

Yeah the fuse is #31 and I think is on page EL-215? Around there somewhere. It runs to the alternator, not sure what it's main purpose is as the diagram shows it running to the alt and thats it.

 

[Flynndog]

Tony I believe that 10A fuse supplies excitation current to the alternator, 10A is "ample" (sorry, couldn't resist). So to throw something else into the conversation, Flynn i think you mentioned that the battery light on the dash is sometimes on? Is it on at the same time that you are measuring <12V at the battery & alternator? As the lamp is illuminated by the difference in potential between the battery and the alternator, when the battery is higher the lamp is on. If excitation current does not reach the alternator, it will not generate.

Hard to say mate, it comes and goes when it wants. It's not on a lot, just may flicker sometimes driving along. I originally had thought it would have been just a loose battery connection but I made sure everything was tight and clean and it made no difference. Because it doesn't come on at idle anymore (it used to) I can't make those measurements.

 

[Old.Tony]

The fuse in that diagram will be to protect the instrument cluster, and pin 35 just happens to run to the alternator - in the diagram, it looks like there's no fuse external to the alternator providing excitation current although the diagram I found for the 2001 alternator shows a 10A fuse heading to the connector on the alternator marked 'S', the fuse being located in the "fusible link and fuse box". Let's assume THIS is the fuse that keeps blowing.

It still makes me think the alternator has a problem. The power going in through that connection isn't going to be great anyway, so it's unlikely that it's a load issue - more likely a fault issue that's blowing this fuse and this is the next job - finding the fault.

The exploded diagram on the following pages shows the regulator as an integral part of the unit, and I notice further on that they specify not only minimum brush length of 5mm for the Mitsubishi alternator (6mm for the Hitachi) but a brush pressure of 487-612grams (Mitsubishi) or 102-350g (Hitachi). Regulated output voltage range for both is specified as 14.1 to 14.7V. There are minimum RPM levels to produce power, looks like the Hitachi is better at producing voltage at low RPM but the Mitsubishi produces more current. Both have shaft RPM minimums (1000-Hitachi, 1300-Mitsubishi) and given the difference in pulley diameter between crank/alternator on mine I'd guess the alternator would be spinning at double the engine rate at least, so idle should produce some power.

 

[Flynndog]

The fuse in that diagram will be to protect the instrument cluster, and pin 35 just happens to run to the alternator - in the diagram, it looks like there's no fuse external to the alternator providing excitation current although the diagram I found for the 2001 alternator shows a 10A fuse heading to the connector on the alternator marked 'S', the fuse being located in the "fusible link and fuse box". Let's assume THIS is the fuse that keeps blowing.

It still makes me think the alternator has a problem. The power going in through that connection isn't going to be great anyway, so it's unlikely that it's a load issue - more likely a fault issue that's blowing this fuse and this is the next job - finding the fault.

The exploded diagram on the following pages shows the regulator as an integral part of the unit, and I notice further on that they specify not only minimum brush length of 5mm for the Mitsubishi alternator (6mm for the Hitachi) but a brush pressure of 487-612grams (Mitsubishi) or 102-350g (Hitachi). Regulated output voltage range for both is specified as 14.1 to 14.7V. There are minimum RPM levels to produce power, looks like the Hitachi is better at producing voltage at low RPM but the Mitsubishi produces more current. Both have shaft RPM minimums (1000-Hitachi, 1300-Mitsubishi) and given the difference in pulley diameter between crank/alternator on mine I'd guess the alternator would be spinning at double the engine rate at least, so idle should produce some power.

Yes that was the blown fuse. What would cause the alternator to not put out a charge until the accelerator was depressed though? Pulley issue maybe?

 

[Flynndog]

Well gents I have found the issue, I believe. There is a short and cut wire in the alternator loom. A piece of the bracket from the surf airbox has rubbed through and cut one of the wires. I can only assume the cut wire is to the alternator (hence the light came on first and later shorts the aircon).

Thanks for the help, I will post some pics soon and once repaired verify that everything works.

 

[Old.Tony]

That shorting wire might be the cause of the alternator problems as well, but certainly is likely to be the culprit behind the aircon fuse. Great job finding it!

Let's see how the alternator behaves after you've sorted that out. I would have thought a pulley/brushes/belt issue preventing the alternator from making enough power, but damaged looms do create unpredictable problems.

 

[Flynndog]

Pics. So all is normal, I ran the car for thirty minutes and the air conditioner held up, which is the longest it has run in 12 months.

The alternator voltage is now at 13.9V at idle from the start, no accelerator required. I assume that the revs provided enough of some voltage across the cut wire/metal contact.

The airbox mount had simply rubbed through the aircon and alternator and cut the other alternator wire. The only way I found it was having a look at the connections and I moved the harness and it shorted.

 

[bods]

Nice job finding that. Glad its all sorted now. Maybe the airbox was trying to get revenge for being put in a Nissan, lol

 

[Flynndog]

Nice job finding that. Glad its all sorted now. Maybe the airbox was trying to get revenge for being put in a Nissan, lol

Hahah, maybe. Got me good. Wait until I get the LC Box in

 

[mitch92]

Good pick-up mate