Solved: Alternator Wiring Testing

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benckj
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Re: Solved: Alternator Wiring Testing

Post by benckj » 22/07/19 22:59

Haven't had a chance to investigate my NA alternator further.

Now my 98 GT is acting strange with unstable voltage levels. Logged a road run and voltage is very erratic & down around the 11.5 at idle and then climbs to 14-15volts at 3000+ rpm. Very strange as it was dead stable at 14.5v when I installed the new alternator a few hundred km's ago. Thinking the 2 failures could be related???

Need to break out the meter and start testing as I don't want to remove alternators again!



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MR2DI4
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Re: Solved: Alternator Wiring Testing

Post by MR2DI4 » 23/07/19 3:50

benckj wrote: ↑
22/07/19 22:59
Haven't had a chance to investigate my NA alternator further.

Now my 98 GT is acting strange with unstable voltage levels. Logged a road run and voltage is very erratic & down around the 11.5 at idle and then climbs to 14-15volts at 3000+ rpm. Very strange as it was dead stable at 14.5v when I installed the new alternator a few hundred km's ago. Thinking the 2 failures could be related???

Need to break out the meter and start testing as I don't want to remove alternators again!
Like I said when I did that full write up on the Alternators and what parts to use in them, the aftermarket "New" Alternators are s#*t if they start using second hand parts in them, in particular the Rectifier Diode pack, its just destined to fail.

You should still get full charge Voltage - 14.6V at idle or you have lost some diodes. From your symptoms you have lost 2 of the 3 branches of the WYE connected coils.

Rebuild your own alternator, its the only way you know what you have got inside. Not hard to do no specialised tools required.

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Re: Solved: Alternator Wiring Testing

Post by benckj » 23/07/19 21:10

That's exactly what I'm afraid of. Had already installed the alternators before following your thread on the sub standard internals. Bought both as 'new' from US so never crossed my mind to tear apart before installing. If it wasn't such a mission to remove I'd just drop and rip into it. First I'll check the wiring through just to confirm its OK. Might be an option to remove back plate without actually removal of whole alternator. How easy is access to rectifier?
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Re: Solved: Alternator Wiring Testing

Post by jimi » 23/07/19 21:53

Black is not a colour ! .... Its the absence of colour
Image

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Re: Solved: Alternator Wiring Testing

Post by benckj » 23/07/19 22:53

Thanks for the link as it re-freshes my memory. I have a couple of old OEM alternators around so may have a quick look at those to get my head around the possible replacement of parts insitu.

I will be severely disssapointed if the 'new' alternators bought contain used parts. This is especially true for the 130amp model that could not possibly use the OEM rectifier.

First thing first, break out the meter and start do some testing. Don't want to jump to any conclusions just yet.

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Re: Solved: Alternator Wiring Testing

Post by MR2DI4 » 23/07/19 23:03

Very easy, just the 3 nuts on the back and that earth screw and the pressed aluminium cover comes off.Also remove the 10mm nut for the main battery connection and all that black insulator comes off the rectifier stud.

Once inside you need a decent #2 Philips screwdriver for a couple of screws on the brushes and the regulator and about 4 screws round the outside of the rectifier and everything comes off the back of the alternator and your left with the core.

I'm not expecting a problem with the "Core" this is the "New" part, its the regulator, brushes, rectifier that can be second hand.

The only trick is you need a thin bit of metal to depress the brushes on re-installation, especially if they are new as they are quite long but the springs are pretty weak.

Post up some pictures, we can critique the parts used ! :laughing

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Re: Solved: Alternator Wiring Testing

Post by benckj » 23/07/19 23:51

OK will do when I get a decent chance to work on the car(s). Weather hasn't been the best and my garage is still in the making!

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Re: Solved: Alternator Wiring Testing

Post by benckj » 29/07/19 22:20

Contacted the seller from my 130amp alternator and he stated all new parts were used. This is one of the main reasons why I bought this particular model from this seller. I asked for a replacement regulator & rectifier (not sure if they are separate or combined) and he agreed to send to me. When I get a break in the weather I'll pull the backside off and remove the suspected parts.

Still need to measure the resistance on the cabling for both cars before doing anything.

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Re: Solved: Alternator Wiring Testing

Post by MR2DI4 » 29/07/19 22:40

The OEM rectifier is pretty easy to spot, even if they respray it. The diodes are pretty small and there are large flakes of lifting paint that come off the black material around the lead side of the diodes. The diodes are easy to test with a multimeter.

The rectifier diode pack is the most likely problem. I can supply you details on how to test everything. You need two multimeters and a variable DC supply to fully test the copper windings in the "core" of the alternator.

I don't have a test for the regulator, but you don't really need one because its simply a process of elimination because you can test everything else.

Post a pic with just the back off before you start to pull it all apart.

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benckj
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Re: Solved: Alternator Wiring Testing

Post by benckj » 30/07/19 4:19

My space is going to be limited if done insitu. I'll try and remove plug to test loom to ensure there isn't an issue with the OEM joins. If that checks out I'll remove the back of alternator and have a decent look at the rectifier & regulator. If easy enough to remove they will be pulled and replaced with the new part. Should it get more complicated I'll try and do some additional tests to pin-point the problem. I have several Flukes, DC power supply as well as megger and a numerous power station Technicians at my disposal.

BTW I've pulled alternators apart before but mainly for bearing and brush replacement. I have noticed the rectifier solder joins and flaking material but never dissected one. From memory they are encased in a epoxy/rubber coating of some description.

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Re: Solved: Alternator Wiring Testing

Post by MR2DI4 » 30/07/19 23:12

Correct but the diodes tend to be kind of "Spot welded" or fused and/or the tab bent over the lead on my new diodes. Solder is not great long term, it has shrinkage with age and is not that strong and fatigues with vibration.

Usually there are some visual signs the diode has gone, that black rubber lifts. They tend to go open circuit, the lead just goes down to nowhere like the diode just evaporated.

The worst part is getting the alternator out of the car, I hated doing it a second time even though it was tested before going in, it just didn't last long.

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Re: Solved: Alternator Wiring Testing

Post by benckj » 18/08/19 22:36

UPDATE

Apologies once again for thread pinching.

96NA- Managed to test the wiring circuit from alternator plug to IGN ECU fuse. Found the resistance was 0.4ohms which shows it has good continuity. RE-checked the alternator plugs main terminals, battery and all fuses. Engine starts and runs fine with no belt slipping or other issues. Still no charge to battery without even the slightest increase in voltage as RPM increased. Keep in mind this was a 'new' aftermarket alternator that worked fine until the car sat over winter and battery was re-charged to get started.

96-3sgte- The alternator does work but the voltage is very unstable (logging info using my aftermarket ECU). No real progress on this as waiting for replacement voltage regulator and bridge rectifier to arrive. Speculation that this is the problem as I would hate to drop alternator again!

On request the supplier sent the parts to me at no charge and plan is to change out components without removing alternator. I did check my old alternators and its fairly logical to pull the brushes and other parts from backside without dropping unit. If I can't get access onto screw terminals I'll remove alternator and lower against subframe. Hopefully, this solves the problem otherwise it will need to come out and be replaced. I do notice it makes a funny sort of whinning noise when running and has done so since it was installed. Guess it could be something with slip rings or internal rubbing that I'll need to find.

More to come.

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