The MR2 Turbo Alternator rebuild guide

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MR2DI4
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The MR2 Turbo Alternator rebuild guide

Post by MR2DI4 » 01/05/19 5:51

Just a post to assist anyone rebuilding there own MR2 MK2 Turbo Alternator.

Okay I managed to get the correct 1992 onward's Diode Rectifier locally. Unless you physically have the replacement in your hand you just not 100% sure its the right part.The 1989-1991 part is different in terms of the main B+ battery terminal orientation, the rest of the rectifier is identical but without the earth strap hole.

So What I have is a Regitar made in the USA RN-10. According to the invoice this is a "120Amp" part.

If you want to buy one in New Zealand, the old type or the new type, you can get it from here:-

https://aespares.co.nz/contact-us-auto- ... al-spares/

Once you know for sure you want an RN-10 is becomes MUCH easier than using the Toyota part number 27060-74330 or the Denso part number 100211-6360 for the complete alternator itself because chances are they have worn off the label thats stuck on the alternator anyway (so you don't even know for sure WHAT alternator you actually even have) and because they are not the actual Denso part number for the diode rectifier it starts to get pretty bloody confusing. Trying to use the actual Denso rectifier part numbers is a nightmare, they just kept changing them.

So using the "RN-10" on E-Bay the number of parts quickly spreads cross multiple parts referencing the part number to include

ARC6018, INR736, W065125

No idea if you could "Upgrade" your 3S-GE using this diode rectifier, if so no point using 35A diodes when you can fit this version with 50A diodes. Someone would need to confirm the stator OD because this was what made searching even more confusing as there is a 118mm and 130mm option Stator, the turbo is bigger at 130.0mm, I measured it with a vernier. I have a bad feeling the N/A MR2 alternator is SMALLER.

You can still purchase the Genuine OEM Denso brush set from Toyota, the part number is 27370-75060. Chances are a new set of brushes and a new rectifier and worst case two new bearings will get you going again for another 20 years.

DO NOT and I repeat, DO NOT rebuild the alternator with the old OEM diode rectifier, even if the diodes measure okay using a multimeter, they are past their use by date. They can short and it would appear the can kill the stator windings when they overheat the copper, melt the insulation enamel coating and the whole alternator is FUBAR. My first original alternators life ended in clouds of smoke its dead.

Easily obtainable from E-Bay in the UK. Complete drama, a day of searching to find it in New Zealand and it cost twice the price of the UK at NZ$112.

Reality is, rebuilding the alternator is pretty easy. Getting the right parts and getting the rebuild right so you don't have to spend another 2 hours pulling it out again in a couple of years or less is the trick part.

Got any questions ? post them here. Been there done that......twice.



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benckj
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Re: The MR2 Turbo Alternator rebuild guide

Post by benckj » 01/05/19 19:33

Excellent info, thanks for following this up. I hit many brick walls when trying to rebuild mine so opted to buy what I thought was a new 130amp model. Yet to see if this is true and will last the distance.

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MR2DI4
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The rebuild of the alternator and the rectifier diodes

Post by MR2DI4 » 01/05/19 23:06

Look its just luck on those Chinese Alternators, it could last 5 minutes or it could last 5 years.The way mine was made, I would predict that it just drifts safely outside the warranty period and then fails.There was clear evidence that they had "Filed" down half the brushes so their goes half the life.

One important technical bit of information that came direct from the Alternator rebuilders and supplier of the Diode Rectifier is the following.

The OEM rectifier has SIX diodes. The Stator is wound it WYE (Star) configuration with the 4th point wired as common or "Neutral" and the more observant among you will notice at this connection point on the OEM regulator the diodes are missing, even though there is clear facilitation in the metalwork to include them if they were required.

The NEW Rectifiers pretty much all come with EIGHT diodes. Now unfortunately my 3-Phase theory was done many moons ago. What I was going to do is simply cut the legs off the correct 2 diodes, however I have been told on good authority that you can just leave the two diodes as they are and they have no effect. Therefore I plan to just leave them, rebuild and get it tested at the same time as my reserve Chinese Alternator.

I spent ages on the net looking for a definitive answer on this but couldn't find it.For a car that is now been around for almost 30 years, I came to the conclusion that there was a pathetic amount of technical information available on the Web in relation to rebuilding the MR2 Alternator.

Anyone who has changed their own cambelt on these cars can also also remove and repair their own alternator. The level of difficulty is about the same.
Last edited by MR2DI4 on 08/05/19 0:01, edited 1 time in total.

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MR2DI4
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MR2 Turbo Alternator old and new versions

Post by MR2DI4 » 02/05/19 6:16

Okay both alternators checked and rebuilt.

The 1989-1991 3S-GTE with power steering Turbo Alternator is on the right, the 1992 onwards versions is on the left.It possibly changed again at some point to an oval regulator plug, I don't know when. Ignore the B+ Battery post thats been cut from DEAD the regulator, I needed it to make the conversion bracket so I can put the new version alternator in the old versions place.

Image

Both will be fully tested by Hope Hickman Auto Electrical on Monday. All going well I have a main and a spare that combined should last at least 150,000km or the life of the car.
Last edited by MR2DI4 on 08/05/19 0:02, edited 1 time in total.

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Testing the Alternator

Post by MR2DI4 » 06/05/19 3:58

Update - both tested and working.

Other bits of information, my old alternator was making a "Whine" , this basically is diodes shorted or open and it causes an imbalance in the magnetic's of the Stator in the form of harmonics. I was told that this is a vibration which then emits sound. In any case, once it starts making a noise that is a bit of a "Whistle" or a "Whine" its stuffed. Almost sounds like a vac leak or something and its actually very hard to identify from where the sound is coming from in the engine bay. Obviously if you pull the alternator belt off and the noise goes away......

I can confirm the extra 2 diodes in the rectifier do nothing, or at least do nothing if all the other 6 diodes are working properly.

Couldn't really load tested to 100 Amp as they are using an actual battery as a load, the maximum I saw was 40 Amps.

Next stage, the refit. The OEM one is going in the car, the Chinese one is going back in its box as a last resort backup and stored in the attic. Probably never end up using it, it will go with the car if sold or be eventually sold separately.

Will post on the run temperature, one thing I noticed was the stuffed one was always running so dam hot I couldn't even hold it after a run.

One thing for sure is if you cannot get another decent alternator, the whole car is stuffed.
Last edited by MR2DI4 on 07/05/19 23:59, edited 1 time in total.

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MR2DI4
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Final note

Post by MR2DI4 » 07/05/19 23:59

So its back in the car with a decent OEM belt from Toyota.

The first thing you notice is it is supposed to run silent, the second is that after a 15 minute run you can still hold your hand on the alternator for several seconds so its in the 40-50 Degree C area instead of the 70-90C area that means you cannot hold onto it.

So if it whines or is to hot to touch, its rebuild time. Even though mine crapped out early, it was really just bad luck and bit of inexperience. Its still better to rebuild your own alternator, that is the only way you know what you have got. A brand new diode rectifier assembly is a must.

Other things of note is that because the charge Voltage is now constant, the fuel pressure and the car idle seems more stable. Charge is 14.8V from cold and after a few minutes this drops to 14.6V. Stable even at idle.

Not expecting any problems from it now for potentially the rest of the life of the car.

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