TL/DR – get a rebuilt Denso.
I’ve been playing with charging problems for a while now. Been a little more serious lately. I have three alternators I’ve been working with for the Land Cruiser and LX450.
Last summer I did a reseal on the Land Cruiser and changed out the brushes and rectifier on the alternator. I did the rectifier because I wasn’t smart enough to realize the voltage regulator was the likely problem. The alternator is working adequately but not perfect.
The LX450 was only getting to mid 13’s on voltage when driving and dropping down into the 12’s at idle, low enough for the ACR for my batteries to open. My main battery was also never getting fully charged but it’s also not getting driven a lot and seems to have a parasitic draw.
I took my spare alternator apart and tested the rectifier and determined it wasn’t working so checked the spare rectifier and it tested good. Swapped the parts, put it back together, installed in the LX450 and it made it about 5 miles before it died completely.
So, I ordered a voltage regulator from ebay and installed it in the original LX450 alternator and swapped it with the dead alternator. It worked great, 14+ volts while driving and high 13’s at idle. It was working so well I ordered another voltage regulator to install in the Land Cruiser. Unfortunately it didn’t last long. A couple days later it’s still working great while driving but dropping to as low as 12.3 volts at idle.
There is a test procedure in the FSM that I have now gone through with the spare alternator. Everything tests fine except maybe the rectifier. If I check using the diode mode on the meter it tests fine. Doing it per the procedure and only checking continuity it fails.
I’ve now spent over a $100 on parts and a bunch of time and I still have three alternators that don’t work as well as I would expect a rebuilt to work.
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