Hey,
I have a 86 22RE pickup motorhome and the alternator is not charging the battery. The vehicle died on me on the way home one day, and since then whenever the truck is running the charge/battery lights stayed on. I also seem to have 2 isolators and a relay wired into the charging system for my dual batteries, but I'm a bit confused on how it's wired in. Figured it might be important to mention, although I seem to be getting excitation and my other readings were as expected (except alternator output)

I followed the steps in this thread https://www.yotatech.com/forums/f116...s-22re-304868/

Basically everything is at battery voltage, including the B post. So the alternator is definitely not working correctly and it seems likely I'm looking at a replacement. What is confusing me is that the charge/brake light is NOT coming on when I turn the ignition (engine off). Both lights come on when I start the engine, which I expect considering I'm having charge issues. However, if I remove the B wire from the B terminal and turn on the ignition, then both the charge/brake lights come on as expected.

So am I missing something there or does this indicate that something else isn't right with my wiring? From what I understood from the post above, the L wire should monitor the output from the alternator, which when I turn the key would would be 0 and that would create a ground that would cause the light to come on. Then when I start the vehicle with a working alternator, the L wire would have voltage from the alternator and the voltage from the other terminal of the fuse would basically cancel out and turn the light off.

I'd also like to pinpoint what exactly is wrong with the alternator, so I can rebuilt it if possible. I've never rebuilt one before and most of the kits I see just have bearings, brushes, and the regulator. How can I determine whether my rectifier or any other component is the issue? I did measure resistance as mentioned in the post above and I included it below with all the other readings. .

Here are the details (keep in mind my battery was draining and not charging while doing these tests):
Vehicle off:
Battery - 12.4 V
B terminal -12.4
B terminal (with wire removed) resistance to case - 0.843 at 2k setting
White S - 12.4
Red IG - 0
yellow L - 0

Ignition on:
Battery - 12.21
White S - 12.14
Red IG - 12.05
Yellow L - 11.84
Charge fuse - 11.65 (both sides)
Charge fuse terminals 11.65 (left) 11.24 (right, the "L" side)
B terminal - 12.16

Engine running:
Battery - 12
White S - 11.8
Red IG - 11.8
Yellow L - 11.4
Charge fuse (both sides) 0.75
Charge fuse terminals - 11.64 (left) .37 (right, the "L" side)
B terminal - 11.8
B terminal with wire removed - 0.75

Also, since I am assuming the issue is the alternator, is there any tricks/tips to removing it? Seems I have to drain and remove the lower coolant hose and the bottom engine compartment plate? F*** that sucks.

 

The most common reason that I can think of that’d makes Brake/Charge light come on would be worn brushes.
Disconnect the batteries, pull the alternator, and inspect the brushes first. You can access the brushes without disassembly. If the brushes are worn you can either solder in a new set or can get a brush holder with brushes already soldered in if you prefer.
But all this is based on having a Denso alternator. If it were me, and the alternator isn’t Denso, I’d probably order a reman Denso unit.

Why Toyota wired the system to have the "Brake" warning light come on with the Charge indicator was always a common question from owners.

 

The weird thing is that I'm getting battery voltage in the L wire causing the lights to not come on during ign, when they should come on. I really only understand the charging system on a basic level atm, but I'm wondering if it's a hint as to why the alt is failing to charge. They do come on when I start the truck, as expected considering I have a charging issue. I plan on researching more about testing the components and testing/examining it further once it's out. I have 2 RVs, only one running atm, so I took the alt out of the one that's not running and plan to put it in for now.

I guess I'll find out if it's a hint once I put this spare alt in. If it still doesn't come on during ign, I'll know it's my wiring or isolator acting up. If it comes on, then I'll know it's something with the alternator and maybe it'll help me pinpoint the issue.

I'll post updates if I figure anything out. I'm having engine performance issues too, so I'll be making more threads around here sometime in the future.

Edit: also what am I looking for when determining whether the brushes are worn? They should be just barely not touching correct?