Alternator for 2006 Tacoma Burning Out

First real thread on TW. I have read up on some people's alternator headaches and would like to throw my issue into the ring.

2006 Toyota Tacoma with JBL Stereo ~117,000 miles.

I recently replaced my head unit with an aftermarket Kenwood DDX9907XR and a T01 datalink by maestro since I am trying to navigate the JBL stock wiring harness and keep my steering wheel controls.

First issue was my head unit randomly turning on and off, still have not solved problem (a different discussion for another day, but wanted to include any and all electrical changes as I move forward to my issue(s) with my alternator(s)).

I also upgraded to a 31M Northstar Pro AGM battery. I redid all of my battery cable wires with tinned copper marine grade lugs. My cables were TEMCO 2 AWG welders cable for the main connections/grounds.

I then went with a

$10 GM 12135037 Multi-Function Diode

GM 12135037 diode, yes I had it pointed in the correct direction, to support the recommended voltage level of the new AGM battery.

Now for the irritating issue I am facing.

My denso alternator went out, so I took it to a mom pop shop where they rebuilt it for $136 bucks with parts from a company called "Transpo".

I think I managed to drive ~500 miles on the rebuilt alternator and it went out again. I read in another TW thread where someone went through 6 alternators until finally buying a Denso alternator from the dealership.

I decided to bite the bullet early and pay $440 for a rebuilt Denso alternator (high price, I know, but time is of the essence and beggars can't be choosers).

My question is, "Is there something else at play here that I am not checking or did I just get unlucky with my alternator going out as soon as it did?"

I am worried to drop the new $440 alternator and it blows because it was something else. Unfortunately this is my daily driver, so I don't have the luxury of doing a full root cause analysis, so I figured buying a quality Denso alternator would be the fix.

A quick note, I did take the GM diode out when I replaced the alternator, thinking that could have been the cause and clearly it wasn't.

I do have an MK3 Mini Blade voltage booster from HKB Electronics shipping and am hopping to use that to support the AGM battery in the future. I would first like to build my confidence again in my setup since currently I am burning through alternators.

 

I'm looking at Toyota OEM parts. 2007 has either 80A, 90A, 130A fitted.

2007 has an internal regulator. You "trick" it with an in-series diode, so it puts out a little higher voltage to keep your AGM battery happy.

Most aftermarket alternators come in, get inspected, tested, and only replace the faulty part! Yes, you paid $136 for the rebuild, but often they are torn down, and "everything looks in spec" and will toss in new brushes and call it good.

I've seen regulators that worked great, but on super hot days (AC on, lots of heat under the hood), you are running close to 150C (about 300F) on the regulator, and it just stops working. They can not test for that at the rebuild facility, and it checked fine at room temp (25C), so it is passed along as "working" and back on the shelf for the next customer.

Denso rebuilds will use new parts. In the past, everything was new; cores are torn down—new bearings, diodes, regulators, brushes if the stator and rotor tested fine (much more rigorous testing).

So with all the new cables, new battery, everything cleaned up, you should be fine with the Denso Alternator.

Source:
https://parts.toyota.com/a/Toyota_2007_Tacoma/63125494__6715197/ALTERNATOR/674470-1903.html

Tooks me a moment to realize diodes are built into the coil assembly—27360 in the diagram. Notice the power grommet (27387). Typically you have six diodes (three positive, three negative). Three phases (Alternating Current) are converted to Direct Current (DC) via the diodes. I've had just one diode fail (so my 90 Amp alternator wasn't quite put out 60 Amps). I've seen diodes overheat and melt the solder out of them! The winding had a short to ground and was hot enough to melt solder (over 300C). Brushes are easy to spot but still prefer old-school-style metal holders.

I worked in a gas station after school—mom Pop three-bay place. We had a lathe in the corner and used to turn armatures and undercut mica. New brushes, send customers on their way with their 63 Chevy Truck. I worked there through high school, graduated in 1976. I never appreciated the old crusty mechanic, but he passed a few years later. Great education. Funny to realize later my college path was electronics, and even today still work with automotive customers. Meanwhile, I'm just a crazy old man mumbling to himself, but in honor of Jim, glad to pass a few tidbits along. It doesn't seem like that was 45 years ago, but thank you, Jim!

 

Super helpful! Thank you.

Makes more sense now. Unless they had a denso 27360 part number around, I am not sure how they replaced it.

Before and after pictures. I am not sure how it managed to work though for another 500 miles, but seems to make more sense that they just cleaned it up and sent me on my way.

They even told me they couldn't find the problem with it and I was told they replaced "rectifier, voltage regulator, brushes, and bearings". I was in and out within an hour.

 

Super helpful video.

https://www.youtube.com/watch?v=1bK0De9XOP0

Correct me if I am wrong, but I believe the coil assembly are just the thin plates that gets used with the diodes and rotor (talking out of my ass here).

I guess my point is, the video shows the rectifier housing the diodes. I am assuming they replaced those parts, but am not certain. Hoping to do a full blown tear down and analysis with the mom pop shop when I replace it with the new denso.

 

I would recommend a full field test, maybe load it up with a resistive bank as well to put it through the paces. If it's rated at 130 amps, I would not hesitate to run it a full load, and maybe even 10% over for a little while to check everything out under stress. As mentioned they don't replace alot of the electronics, only consumable parts such as brushes, or bearings if worn. It's cheaper for you to rebuild yourself if you have the time.

https://www.maniacelectricmotors.com/40wal11.html

 

Nice find on those parts. The Toyota sells the windings & diode plate as a $711 assembly (ouch).

With a full load (Air Conditioner on, blower on high, lights on, radio blaring, wipers going, etc.), the voltage should still be higher than before the vehicle started. I have my trusty old Fluke meter. I'll read battery voltage, say 12.5V. Start the car. It should read about 13.5V (1V higher) flip on all loads, and it should still be putting out about 13V.

The modern (3rd generation) with the ECU playing measuring voltages and adjusting can mess you up, but those basics still apply.

I had an old bench set up, motor, belt, alternator, and a bunch of 100W driving lights. Old alternators were only 30Amp or 50Amp affairs (back in the days of 20R). I went crazy load testing and finding odd things—diodes that "leaked" (dead battery after three days). I have a Tektronix 575 curve tracer (boat anchor), but the power stage is acting up.

A Good voltmeter is a handy tool.

That website is a gold mine of neat tips. Thank You. I use Thomas and Betts Battery Cable connectors. Crimped. Yes, I still have a solder pot for tinning leads, but a proper terminal and crimp are fine. Corrosion is the enemy of electrical systems. After going through everything with my 2021, I really want a clean 2005 Taco for reliability!

Good reading (It's on a WRX, but the same ideas apply).
https://sep.yimg.com/ty/cdn/yhst-44365514171686/UpgradeWireSVX.pdf?t=1620847274&

 

Well, I feel pretty stupid at this point but I will chalk it up as a learning lesson.

So when I replaced my cables, I also replaced the cable in my fuse box (Power Distribution Center I think is what some call it). I replaced it because it would not reach the new battery. I must have tugged on the alternator wires when I was unplugging the connections.

After replacing those cables, my alternator went out. I thought that I shorted something or the diode I was using damaged it. I had the alternator rebuilt. Less then 500 miles later, it stopped working again. I just replaced the alternator with a REMAN Denso from the dealership and that one wasn't working. At this point, I knew that it was something else. I rechecked the fuses, relays, and connector. It started working when I jiggled the wires that were sitting in the fuse box.

Man that is frustrating, but nonetheless, everything is working now and I guess I now have an extra alternator for a rainy day.

Anyone know if there is a part number to replace that harness, not that it is completely necessary.

I really appreciate yalls help and insight!

 

I've always wondered about Maniac Electric Motors or alternatorbrush.com When I rebuilt my Honda's Mitsubishi alternator, a Maniac rebuild kit was $40. Not fully trusting the quality of a $40 kit, I spent $300 buying the rectifier, regulator and bearings from HondaPartsConnection.

I'm really curious about the quality of the Maniac kit, has anyone used them? After successfully rebuilding my Honda alternator, I want to rebuild the Denso alternator in my 2006 Taco using OE parts. But, just the regulator from Toyota is $245. ToyotaPartsDeal has it for $180. Bearings are another $50. I can't find an authentic Denso voltage regulator anywhere online.