Fitting an Internally Regulated Alternator to an MQ

[adam.s]

My old alternator is shagged (externally regulated), and the one I got to replace it is actually internally regulated.

I am told I can bypass the external regulator, has anyone done this before?

[adam.s]

Okay I have since jumped the Field connection in the MQ loom and both

* the charge light goes off (GOOD)
* the alternator kicks over and is giving me a solid 14V (GOOD)

So what I can see, the car is charging, and working okay -- EXCEPT the main fusable link is getting VERY hot and smoking (hasn't completely shat itself yet but I'd say if I didn't catch it then it would have).

So I really have no idea whats wrong now, does anyone have any ideas?

Thinking the next step is to get an auto electrician to check it out.

[adam.s]

I had a look at a mates MQ and his fusable link wire is yellow, mine is red.

Color Wire Gauge
Black 12
Red 14
Dark Blue 16
Grey 18
Orange 20
White 22

Closest thing in that table (I found on the net) is orange, which means its only 12 amp more - I don't think it would be that.

I really can't see any difference between what is on his car and mine, and before this alternator swap I didn't have any electrical problems.

Really is shitting me to tears

[murcod]

I'm not too familiar with external regs, but have played around swapping alternators and rewiring the looming to suit.

Do you know if your new internal reg has got a voltage reference terminal? Some of them require an external reference input- others don't. Apart from that you should have an ignition terminal (wire to 12V ign on) and a terminal to go to the warning light on the dash.

The alt output terminal should go straight to the battery positive via a fusible link. You may find (like I did) that there will be other wiring branching off the alt -> batt cable on your factory loom, so you may not be able to simply run a new cable like I tried.

[adam.s]

Well the only thing I can think of, is this new alternator is a higher ampage and is pumping out more current at a lower RPM (compared to the old one).

I have sorta found on the net that yellow is 20 amp fusible wiring, and red is 10amp.

My mates MQ which has been rewired for internal regulation, has yellow fusible link.

Which makes me wonder why I have only 20amps of fuse (ie, 2x 10amp (red)).

Anyway, that gives me a couple of things:

a) My car should never have had 20amp fusible link, and it's just a ticking time bomb.

b) I should instead have yellow fusible link which gives me 40amp (on what I thought was a 50 amp alternator - factory MQ) which sounds a hell of a lot more sense then having 20 amps.

But it doesnt explain why this new alternator is making the fusible link shit itself.

and

c) 20 amp is a helllll of a lot of current to be pulling thru those little factory loom wires, so maybe it is supposed to be that small.

I think I might just put it all back together and take it to an auto electrician.

Just increasing the fusible link to 40 amp's can't be good, it's probably a recipe for a nice engine bay fire

[adam.s]

Do you know if your new internal reg has got a voltage reference terminal? Some of them require an external reference input- others don't. Apart from that you should have an ignition terminal (wire to 12V ign on) and a terminal to go to the warning light on the dash.

As for this, it is basically the same setup as the other alternator except it doesnt have the external regulator.

All the wires are the same except for 1 (as far as I can tell) - the field exciter, which I wired in the same as how it was done in my mates MQ.

The alt output terminal should go straight to the battery positive via a fusible link. You may find (like I did) that there will be other wiring branching off the alt -> batt cable on your factory loom, so you may not be able to simply run a new cable like I tried.

Nah there is nothing else branching off so I think what I might do is get a much higher current cable and fusible link for 40 amp and try that.

Will talk to an auto electrician first anyway, don't wanna cause more damage then needed

Thanks for your advice, will let you know how it goes.

Cheers

[murcod]

My thought would be that the fuse should be at least the same rating as the max alternator output current.

[chimpboy]

Well the only thing I can think of, is this new alternator is a higher ampage and is pumping out more current at a lower RPM (compared to the old one).
...
c) 20 amp is a helllll of a lot of current to be pulling thru those little factory loom wires, so maybe it is supposed to be that small.

Just to clarify, the alternator's amp rating is the most it can supply, but it will only supply as much as the system demands. So if your vehicle was only drawing 8 amps (or whatever) before, it will still only draw 8 amps now.*

I may not be fully understanding the issue here; it sounds like you're saying the loom is pretty lightweight..?

The wire from your alternator to your battery should be reasonably fat; then the loom from the battery to everything else in your car should have its own fuses in various places so you shouldn't have to worry about what happens after you've gotten alternator current to the battery. If the wire currently going from your alternator to your battery is thin/light, replace it with thicker wire - wire that won't roast if it's carrying 40 amps.

Jason

*edit: a complicating factor is that the battery may now try to charge faster than it used to be able to, drawing more current... hence another reason to make sure the alt->batt wire is beefy. Your new alternator probably also sits at a higher voltage than the old one did.

[adam.s]

Well the only thing I can think of, is this new alternator is a higher ampage and is pumping out more current at a lower RPM (compared to the old one).
...
c) 20 amp is a helllll of a lot of current to be pulling thru those little factory loom wires, so maybe it is supposed to be that small.

Just to clarify, the alternator's amp rating is the most it can supply, but it will only supply as much as the system demands. So if your vehicle was only drawing 8 amps (or whatever) before, it will still only draw 8 amps now.*

I may not be fully understanding the issue here; it sounds like you're saying the loom is pretty lightweight..?

The wire from your alternator to your battery should be reasonably fat; then the loom from the battery to everything else in your car should have its own fuses in various places so you shouldn't have to worry about what happens after you've gotten alternator current to the battery. If the wire currently going from your alternator to your battery is thin/light, replace it with thicker wire - wire that won't roast if it's carrying 40 amps.

Jason

*edit: a complicating factor is that the battery may now try to charge faster than it used to be able to, drawing more current... hence another reason to make sure the alt->batt wire is beefy. Your new alternator probably also sits at a higher voltage than the old one did.

Is there a rule for what that main fusible link should be though?

I have checked 4 other MQ's and none of them have the same value fusible wire lol

[Heathx4]

Yeah, what chimpboy said. I replaced my alternator a while back, and then had some dramas with the dual battery setup. Long story short, I let the smoke out of the batt<->alt wire trying to jump start it. Turned out it was a crap piece of wire, and had an auto elec have a squiz. Basically all they did was replace fusable link (I'll check colour for you) and then ran an extra dedicated wire between batt and alt (can't remember the details, will have to check tomorrow). Like chimpboy says, regardless of what your car is drawing (which should be protected by individual fuses), you want that batt<->alt link to be pretty chunky to handle the amps when charging a flat battery.

[adam.s]

IS FIXED (well I have realised the problem)

I actually had a different battery in the MQ (from one of my other patrols), and its a deep cycle marine battery - apparantly draws a lot more current when charging.

I swapped in the old crappy super cheap 500cca one and it is fine, so I need to run a higher ampage wire from the alternator with a bigger fuse.

As for the size of the fuse ?? - I think I will buy a few fuses and try it out, I was reading either on the net or on this board that 30 amp's should be sufficient per battery.

So basically what chimpboy/heathx4 are saying as well is what the problem ended up being.

I'll go down to jaycar later today and buy some fat cabling.

Thanks guys - champions.

[chimpboy]

If you're on the north side of Brisbane or don't mind going to Geebung, there's a guy I used to get cable from (before I moved back to Melbourne) who was really good price and quality wise.

It's Cameron's Cable Accessories (also good for heatshrink, lugs, and other useful bits and pieces) in Geebung. Ask him for red cable that will handle the job. He should also have suitable lugs. Just ring first to see if he can do it by the metre because I only ever bought full rolls.

Otherwise something like this will certainly do the trick: http://www.jaycar.com.au/productView.asp?ID=WH3066

Or you could just cut up an old jumper lead

Jason

[adam.s]

oh true

i have some 4 guage stuff leftover from my old car's stereo install so should be able to use that

might go visit this geebung place just to have a look anyway - cheers!

[adam.s]

Okay for future reference (and the nissan bible), if anyone is looking to fit a different alternator to an MQ (in particular):

a) You need to disconnect the old regulator (I left mine in there for the moment incase I need to swap alternators again but it is looking fine for the moment).

b) You need to short the red/white and white/black wire in the connector that goes to the factory regulator. I made up a short jumper lead with two spade connectors and they fit perfectly.

While you are at it:

c) Good chance (like everyone else has said) that the wire running from the alternator to the battery is a peice of shit and needs to be replaced.

Now to get my air con running

[V8Patrol]

Added to the good book