Hi guys

 

300zx Fairlady, 1991, J reg, Jap import, 90,000km

 

I have a problem with my alternator and had to call the AA out the other day because the beast wouldn't start, although it had been fine 20 minutes beforehand. It's a problem I've had in the past several times.

 

The AA guy put a meter onto the battery (sorry, not technical here :)) and told me that it should read somewhere between 12 and 14. It was fine when just the engine was running, dipped when he switched on the headlights and dipped even further to 10.8 when he put on the rear window heater and air con.

 

He told me that the alternator is faulty and that I should avoid using anything other than the engine and not drive it at night until I get it sorted. It started immediately when he jumped it and has been fine since although I haven't used it with lights or anything else.

 

My partner has suggested that the brushes in the alternator may be worn and that replacing them might help. What do you guys think? Do I need a new alternator or is it likely to be worth replacing brushes? Can they be replaced?

 

Next question is likely to be how the heck to change the alternator and where on earth to get one from LOL

 

Thanks in advance for your help as always :)

I got a used one m8 can have it for £40 delivered. The difficult part is the loom thatgoes into the back as far as fitting is concerned Iirc

You need to take a close look at the fusable link in the little fuse box on the O/s front fire wall area.

Its the link which looks like a wire loop. check that this link has not blown as this will break the connection to the alt if it is. pull on the link wire to see if it is broken within it sleave.

The alt on Z's are almost bullet prof.

Iv only ever change 1 in twenty years working on these cars so check everything else first mate.

daz

D2

Hi guys

 

Still having alternator problems. Have checked the fusable link as suggested by Daz and it seems to be fine. Can this be tested with a voltmeter? Would it not cause problems with the other functions this is linked to if the link is damaged? ie, the links adjacent controlling the rad fan, stop lamp, ign, skid contr, ltg, p.wdw, p seat, fuel pump and egi inj?

 

Is it possible to get the brush pack out without removing the alternator? And also if we do need to remove the alternator, my partner has had a look underneath, swore a lot and went "eek" and said and it seems the anti roll bar needs to be removed to remove the alternator? Is this the case?

 

Any further advice please?

I had starting issues with my 300 when i first got her, and was told it was the alternator. I got it checked and was not the case, the problem was a bad connection (earth i think) to the stater, quick fix and has been fine. HTH.

 

Al.

Thanks Alan - will check that out - assuming I can find the starter motor :lol

Get your reading glasses on..........:cool2:

 

Problems in the charging system show up as either an undercharged or an overcharged battery. The first is easy to spot, with poor cranking or the need to jumpstart on a regular basis. The latter usually manifests itself in loss of the electrolyte and the swift degradation of the battery due to hardened plates and an inability to accept a charge.

Before condemning the alternator, though, especially with an undercharged battery, take a look at a few obvious potential causes, such as slipping belts, loose or corroded battery terminals or terminals separated from the battery. You might also check that there is not a parasitic load that is always on, draining the batteries especially when your 300zx is shut down over a weekend, for instance. Another cause of poor cranking current is an internal short in a battery.

If your 300zx electrical system has been worked on at some stage in its history, the size and capacity of the wiring between the alternator and the battery should be verified to ensure there is not a major voltage drop between the two electrical components.

If all this checks out, undercharging is most likely a problem within the alternator. The diode pack may be defective or there may be an open circuit or grounded rotor coil.

To check the current output of the alternator you can place an ammeter in series between the ground terminal on the alternator and the ground battery lead. However, since running the alternator on open circuit can destroy the diodes, you may be better to place an inductive clamp ammeter on to the battery ground cable. Such ammeters are relatively poor at measuring low currents, but since the alternator is tested with full load, the inductive ammeter is accurate enough and saves disconnecting terminals.

With a voltmeter across the battery terminals and a full load for the circuit, start and run the engine to get maximum alternator output. This may be as much as 2,000 rpm.

As all accessories are turned on, the battery voltage will drop. At 12.6 volts, the alternator regulator should apply full system voltage to the field and the alternator should be producing its rated current. If the ammeter shows within 10%-12% of rated power, the alternator is okay.

As the alternator charges the battery and system voltage rises, the charging rate should taper off. Somewhere between 13.8 and 14.5 volts, the output should be very small. If the system voltage rises above 15 volts, the batteries will overheat and might even spew out electrolyte through vent holes. This condition indicates a faulty diode pack and a garage can replace this part of the alternator, more simply, retrofit a rebuilt/tested unit.

To test for high resistance in either of the charging wires, connect the voltmeter between the output terminal of the alternator and the battery positive terminal. There should be less than 0.2-volt difference. Check the ground circuit for the same voltage drop. High resistance here will give a large voltage drop and account for undercharging.

 

This may seem like a lot to take in, buts its not that bad...really....honestly....:w00t:

:scared: :scared: :scared: :w00t: :w00t: :w00t: :blink: :blink: :blink:

 

Good write up matey!!!! :thumbup:

 

Al.

:angel:Thats very nice of you mate, we can but do our best.

Thanks very much for that Osty, some very useful information there. Wish you lived next door :lol: