HELP - Mystery Relay or Ignition Switch? (1 Viewer)

[cheddar bob]

97 LX450, ran perfectly before I went in for an alternator upgrade. Here's what I did:

-150A Denso reman alternator installed with photoman's kit.
-New 2 gauge wires from B post on alt to battery (fused) and same wire for batt to block ground.
-Unhooked stock charge wire from alternator inside AM1 fusible link box, taped off and tucked aside.

When I originally redid the connector for the Sequoia alternator I had the black/blue IG (ignition) wire in the wrong spot, going to the "M" terminal on the Sequoia alternator, which is left blank on our cruisers. See here: https://forum.ih8mud.com/threads/upgrading-stock-alternator-to-130-150-amp.206807/page-2
I'm not sure what the "M" terminal on the Sequoias does but if it puts out 12v, not good.

Identified the issue and swapped the IG wire to the correct spot. Started her up, ran perfectly fine. Checked out everything with the multimeter, all seemed well. Went to drive it the next day and the battery was deader than a doorknob, so dead nothing came on. Jumped it off, let her idle and got the battery recharged. Shut it down and started again a few mins later and it was idling really low. The battery was unhooked for about a week so I'm not sure if this is the computer adjusting or if it's related. Shut it down for the night and unhooked the battery again thinking I fried a diode in the alternator and it's draining my battery.

Today---get in to move it and it cranks but won't start. Here are the symptoms:
-Interior lights and windows work
-Starter cranks

With key on:
-Got 12v at the coil
-No power to radio
-No power to OBD port (Ultragauge is dead)
-No power to A/C blower motor

-I checked all fuses, even the 30, 50, and 60A ones.
-Fusible links check out
-Checked the POWER and OPEN CIRCUIT relays in driver kick panel
-No spark (yes I sprayed something flammable in the TB)

What am I missing? Fried ignition switch? Relay fried somewhere I haven't checked yet? I've been studying the EWD and nothing is popping at me. As long as I didn't fry the ECU, we'll be golden. Help me out!

 

[cheddar bob]

Also wanted to add the voltage light above the voltage gauge flickers with the key on.

 

[cheddar bob]

The more I read and stare at the wiring diagrams the more I keep coming back to the fusible link that feeds the under hood fuse box. I definitely don't think it's the ignition switch anymore and I can't find a common relay to all of the symptoms.

I don't remember if the check engine light was on when the key was on last night.

I'm going to use a jumper to test the fusible link in question tonight. Any help is still appreciated, but I will report back.

 

[cheddar bob]

Just to tidy this up since it drives me nuts when I find a thread with no solution, the alternator was the culprit, here's why:

Wired sequoia plug wrong initially, burned up diodes in alternator.
I had left both white wires on the B+ post of the alternator, unhooking the larger charge wire at the fusible link box after adding new 2AWG charge wire from alternator to battery.
The EFI fuse and relay feed off the large white wire.
The way it was hooked up, 12v has to travel from the battery through the larger 2AWG charge wire then over to the large white wire on the B+ post of the alternator, then up the large white wire to the EFI fuse.
Since the diodes were bad in the alternator, it was dissipating most of the 12v and only allowing about 3v to reach the EFI fuse, thus not allowing there to be enough power to run the ECU.

 

[baldilocks]

Just to tidy this up since it drives me nuts when I find a thread with no solution, the alternator was the culprit, here's why:

Wired sequoia plug wrong initially, burned up diodes in alternator.
I had left both white wires on the B+ post of the alternator, unhooking the larger charge wire at the fusible link box after adding new 2AWG charge wire from alternator to battery.
The EFI fuse and relay feed off the large white wire.
The way it was hooked up, 12v has to travel from the battery through the larger 2AWG charge wire then over to the large white wire on the B+ post of the alternator, then up the large white wire to the EFI fuse.
Since the diodes were bad in the alternator, it was dissipating most of the 12v and only allowing about 3v to reach the EFI fuse, thus not allowing there to be enough power to run the ECU.

Is a 2AWG charge wire necessary? I recently had a 140A alternator custom made in an original case in order to avoid bracket mods. When I asked, the builder told me an 8AWG wire would be sufficient. I believe what is in my 94 model is an 8AWG charge wire and the one that runs to the vehicle is 10AWG. He suggested adding a second charge wire instead of removing any existing wiring. I see other threads here where guys have upgraded to huge charge wires and it makes me wonder because my last crawler had a 150a alt and I used 8AWG charge wire with no problems and I used the winch a lot. I appreciate the info you provided above though.

 

[cheddar bob]

You'd be OK just adding a second charge wire for the extra amperage. I used 2AWG wire because overkill, and it's what I was using to upgrade grounds and link the dual batteries. The T-Max dual battery kit I bought came with 6AWG.