Solved: Alternator Wiring Testing

This section is for technical Q & A
Please try the search function before starting a new thread.
Forum rules
Many subjects will have been discussed before. Please try the search function before starting a new thread.
Check in the Know Your 2 as the information you need may already be there.
Important ! - Please make your topic title as descriptive as possible . titles with just "help" generally dont get as many answers as a title that points to the problem
User avatar

benckj
Posts: 236
Joined: 05/04/06 1:00
Gender: Male
Years of MR2 Ownership: 5
Location: Alexandra, New Zealand

Re: Solved: Alternator Wiring Testing

Post by benckj » 27/08/19 5:15

Thanks for the words of encouragement Carl. Updated last post to include that alternator & parts dropped off to Sparky along with my long story. Wish dropping my turbo alternator was as easy as you say but afraid not the case due to my aftermarket exhaust and A2W heat exchanger located under rear boot.

On the bright side both alternators have brand new parts installed and look in great condition. Proof will be when testing but initial resistance tests look OK. I'll attach some pics of the NA alternator and turbo replacement parts for reference.
You do not have the required permissions to view the files attached to this post.



User avatar

MR2DI4
Posts: 1153
Joined: 20/04/11 23:18
Gender: Male
Years of MR2 Ownership: 21
MR2's Owned: 1
Real Name: Carl
Location: Auckland >>> New Zealand

Re: Solved: Alternator Wiring Testing

Post by MR2DI4 » 27/08/19 8:24

Use the diode setting on your multimeter if you have it, not an Ohms range setting. Any decent meter will have a Diode setting these days its pretty normal.

Its unlikely any of the windings are stuffed. From memory you have 3 Ohms between the slip rings that the brushes touch on and you need a high current setup to test the actual stator resistance which from memory was 0.018 Ohms for each of the 3 windings but just a very low resistance continuity check to make sure its probably ok may do it. If you know what your doing you can check for shorts between the windings and an insulation test to earth.

Yes the parts already installed look new to me so no idea why you have had failures.

User avatar

benckj
Posts: 236
Joined: 05/04/06 1:00
Gender: Male
Years of MR2 Ownership: 5
Location: Alexandra, New Zealand

Re: Solved: Alternator Wiring Testing

Post by benckj » 27/08/19 10:04

I used the diode setting on meter but did not get the results I expected. Would not have thought they are zenors but something doesn’t match the OEM test.

I have the equipment to test stator windings but like you indicated I seriously doubt that is the problem. All the same the Auto Sparky can diagnosis the issue, replace what’s required and actively test alternator on dyno. I’ll get home to measure full output current.

Once I know the fault I can hopefully determine the cause. Still speculating it’s my old Repco charger although it checks out on voltage outputs. Usually I use my 3 stage smart charger but it got left outside overnight and since has an intermittent fault. Might need to chuck both in the bin and buy something decent.

User avatar

MR2DI4
Posts: 1153
Joined: 20/04/11 23:18
Gender: Male
Years of MR2 Ownership: 21
MR2's Owned: 1
Real Name: Carl
Location: Auckland >>> New Zealand

Re: Solved: Alternator Wiring Testing

Post by MR2DI4 » 27/08/19 22:50

They are not Zener diodes they are a high current silicon rectifier diodes. Specification wise they are 25 to 50Amp diodes depending on the maximum current output of the alternator. They should be open circuit one direction and something like 0.5V in the other direction.

Find an auto electrician then can put it in their test jig and spin it up and load it. I managed to get both of mine tested for $10 it only takes them a couple of minutes. They know what to look for like a smooth output increase with increasing rpms.

The smart chargers are the go, build two of them probably 15 years ago now before they were even on the market. Chargers are far right, used a commercial 6A switchmode supply and the dedicated board for the charger.

Image

User avatar

benckj
Posts: 236
Joined: 05/04/06 1:00
Gender: Male
Years of MR2 Ownership: 5
Location: Alexandra, New Zealand

Re: Solved: Alternator Wiring Testing

Post by benckj » 05/09/19 4:35

Collected the NA alternator and parts removed from turbo (rectifier & regulator) from the local auto-sparky. He was really easy to deal with and more than happy to swap parts around into the NA alternator for testing. Seems checking the rectifier on the bench is easy enough but regulator is not. Also learned that the rectifier may in fact bench test ok but fails under load. I like these parts to be tested as best as possible in the device they are operating.

The final result was a blown rectifier on the NA and a noisy/faulty regulator on the turbo. As the supplier sent over both these parts I was able to ulitise them without buying anything else.

Now comes the fun bits as I have both cars pulled apart. The NA alternator was completely removed but turbo I was able to simply pull backing plate off and un-bolt the internal parts. Couple of pics attached that shows the components which were all new (not refurbished). Note the difference with the regulator and tabs on underside which are joined onto internal pins. Faulty one on RHS doesn't have the tabs connected so not sure what this means.
You do not have the required permissions to view the files attached to this post.

User avatar

MR2DI4
Posts: 1153
Joined: 20/04/11 23:18
Gender: Male
Years of MR2 Ownership: 21
MR2's Owned: 1
Real Name: Carl
Location: Auckland >>> New Zealand

Re: Solved: Alternator Wiring Testing

Post by MR2DI4 » 05/09/19 18:35

I have stuck to the genuine Toyota Regulators, they have not failed on me yet just the rectifiers.

Yes the rectifiers tend to fail once they get a serious load, thats when mine went because I didn't fully charge the near flat battery before fitting the new alternator. Yes it can handle it when new but some 30 year old parts are just not a good idea.

Wouldn't worry about the wires to the tabs on the regulator, as long as it works your fine. Unfortunately these are full of plastic encapsulated electronic components and they are going to be nowhere as reliable as the Japanese OEM version.

There is a fair chance the rectifier is also going to be "censored" if its made in China, Mine cost NZ$112 and it was made in Germany.

IMO if you factor in your time to fix an alternator in an MR2 its not worth your time using cheap parts. On some cars the alternator is out in 5 minutes, the MR2 can take you hours.This doesn't even factor in the chance that it craps out on you while your in the middle of nowhere and you have to pay to get it towed.

User avatar

benckj
Posts: 236
Joined: 05/04/06 1:00
Gender: Male
Years of MR2 Ownership: 5
Location: Alexandra, New Zealand

Re: Solved: Alternator Wiring Testing

Post by benckj » 05/09/19 22:11

The Denso OEM parts I have from the removed alternators do seem much more robust although are showing their age. The regulators indicate a degraded state with 'white' corrosion evident on all the terminals. Rectifiers look as though they have been through some serious temperatures issues with diodes overheating and bubbling the plastic away. Solder joints look in very poor condition and have a possibly high resistance or even open circuit.

Time will tell how long the new alternators & internal parts will last. I will try and source some good replacement parts in the event I have another failure down the line. The auto-Sparky stated that when they rebuild alternators they use the same brand components I was installing.

Most MR2 owners would have no idea on how well their alternator & charging circuit is preforming. I have voltage displayed on my touch screen and set tight alarm paramters to show any changes. I also data log road runs often to monitor my engine performance and voltage is included on the log. This is what alerted me to the noisy voltage levels and steep charging steps. Old pic of my display below for reference although I've updated and changed quite a bit over the past year.
You do not have the required permissions to view the files attached to this post.

User avatar

MR2DI4
Posts: 1153
Joined: 20/04/11 23:18
Gender: Male
Years of MR2 Ownership: 21
MR2's Owned: 1
Real Name: Carl
Location: Auckland >>> New Zealand

Re: Solved: Alternator Wiring Testing

Post by MR2DI4 » 05/09/19 23:26

I agree I got away with driving mine in what was a "Faulty" condition for thousands of km's but sooner or later it totally dies on you.

Effectively its a "Three Phase" system and you can loose one phase and it still appears to work in terms of the your warning light not coming on but as soon as you loose the second phase your in trouble.

If you have an oscilloscope you can put it on the battery while the car is running and you can see the three phase ripple Voltage which appears as 14.8V on your multimeter.

The easy check is it should be running totally silent and you should have 14.6 to 14.8Vdc charge Voltage across the battery even at idle or 750-850rpm.

On the way out it also appeared to upset my idle which is usually dead stable. Probably because the unstable Voltage it was affecting the fuel pump.

All in all its the one thing you want working besides the engine itself or about 30 minutes of run time (or significantly less depending on your battery capacity) after it dies your left stranded somewhere.

User avatar

benckj
Posts: 236
Joined: 05/04/06 1:00
Gender: Male
Years of MR2 Ownership: 5
Location: Alexandra, New Zealand

Re: Solved: Alternator Wiring Testing

Post by benckj » 06/09/19 2:11

I suspect that I dropped one phase on the turbo and lost all on the NA. As you indicated, monitoring the voltage level at idle is generally a good indication of charging circuit health. Most likely no warning lights will even be shown for this problem and battery will remain charged enough for most people to never notice.

Task this weekend will be firstly install new rectifier & regulator in the turbo and get that up and going. Following that I'll install the alternator back into the NA which happens to have the rectifier that came from turbo. Hopefully, all goes to plan as weather is closing in and there is already snow on them hills..

User avatar

MR2DI4
Posts: 1153
Joined: 20/04/11 23:18
Gender: Male
Years of MR2 Ownership: 21
MR2's Owned: 1
Real Name: Carl
Location: Auckland >>> New Zealand

Re: Solved: Alternator Wiring Testing

Post by MR2DI4 » 06/09/19 3:07

Good luck let us know how its goes.

The only problem is that I suspect that these aftermarket alternators only have a design life of 6 to 8 months before they crap out.

User avatar

benckj
Posts: 236
Joined: 05/04/06 1:00
Gender: Male
Years of MR2 Ownership: 5
Location: Alexandra, New Zealand

Re: Solved: Alternator Wiring Testing

Post by benckj » 09/09/19 5:17

Some progress over the weekend although not as much as I would have liked due to poor weather on Sunday.

Managed to get the new parts installed into the turbo alternator and button it up. Car fired up on first pop and monitoring voltage at idle was only around 12.8. After reving slightly it jumped to 14.5 and stayed between this & 14.8 regardless of RPM. Still want to run a data log while under load and make sure its dead steady before I'm happy. Battery will need a good charge before idle voltage is steady.

Will get to NA soon enough. I'm certain the alternator is repaired as it was test run a sparky shop. I have more room to work on NA but as bracket was removed need to install this first. Shouldn't be an issue just time I don't have at the moment.

I'll be severely disappointed if I only get 6-8 months out of them. They both have a life time guarantee although I would think it must be returned to US. Where do you get the Denso Regulators & rectifiers from?

User avatar

benckj
Posts: 236
Joined: 05/04/06 1:00
Gender: Male
Years of MR2 Ownership: 5
Location: Alexandra, New Zealand

Re: Solved: Alternator Wiring Testing

Post by benckj » 16/09/19 0:06

NA alternator installed & tested. Stationary runs at approx 14.5v regardless of RPM. Problem was rectifier and I replaced with the one which was on my turbo.

Turbo is better than before but still not very stable during a 20m road run. At idle its drops to approx. 11.8v and after around 1000RPM runs between 14.2 and 15v. I need to snip a bit of the datalog and place here for comment.

Maybe I'm getting fussy but thought it should be better than this. Could possibly have something else noisy with car on the load side as I run multiple pumps & motors (A2W, WI, PS, fans, etc). Alternator still makes a 'whirrling' noise when running. Have confirmed brushes & slip rings OK and it rotates fine by hand with no obvious obstruction or resistance.

User avatar

MR2DI4
Posts: 1153
Joined: 20/04/11 23:18
Gender: Male
Years of MR2 Ownership: 21
MR2's Owned: 1
Real Name: Carl
Location: Auckland >>> New Zealand

Re: Solved: Alternator Wiring Testing

Post by MR2DI4 » 16/09/19 7:12

Voltage should be dead stable on 14.6V regardless of everything else as long as the battery is not dead flat, even then it should come up pretty quick.

Unlike a modern car there appears to be no "Smarts" in the alternator charge Voltage. My 2005 Subaru Voltmeter is all over the place, it kicks in at over 14V but depending on rpm's and whats turned on in the car it can drop to 13.8V or I have seen it drop right off even lower for brief periods.

I would say you still have a problem with the Turbo alternator. No Voltmeter in my MR2 but the fuel pressure gauge at idle gives you a rough idea of whats going on.It used to be all over the place now its as stable as.

User avatar

benckj
Posts: 236
Joined: 05/04/06 1:00
Gender: Male
Years of MR2 Ownership: 5
Location: Alexandra, New Zealand

Re: Solved: Alternator Wiring Testing

Post by benckj » 16/09/19 21:34

I tend to agree with you and would like to find the issue. Can probably survive as is because it does work and I need to have operational for a few trips coming up. Road trip & ttTrack day in Nov which I'm hoping to make if I can get my boost spikes under control.

I'll snip a few bits of the datalog which show voltage, rpm, duty cycle, MAP, etc and see if any ideas come to mind. May simply turn into a grounding issue with my alternator, EMS or something similar like unbalanced load on circuit. Don't know so I'm open to ideas.

Post Reply

Return to “MK2”