Mysteries of Electricity (1 Viewer)

[Rumblefrog]

Vehicle: 1984 FJ60 with 1HDT / H55 transplant

I was driving merrily along, accelerating through the gears, when I noticed that when I reached 2000 rpm, my Charging System light started flashing. When I would slow to below 2000 rpm, the light would quit flashing. I got on the freeway and accelerated to approximately 65 (2000 rpm-ish), and the Charging system light started flashing again. I headed for home, and after a while, the light quit flashing, and my voltage - normally around 14 volts - dropped to 12 volts and would not move no matter have fast or slow I revved. I have two batteries, so I managed to make it home with plenty of battery left. I pulled into my garage and shut the engine off.

This all sounded very "alternatery" to me, so I pulled the alternator and had it tested; it checked out as okay. Nevertheless, fearing that it might be something intermittent in the alternator, I bought and installed a new one (only $599! ). I went to start the truck and see if the new alternator made any difference, but the truck wouldn't start. It cranked and cranked but wouldn't fire. I started trying things and found that the various Key On/Engine Off accessories would not work. I tested the glow plugs and fuel solenoid and found that neither of them were getting voltage. The radio and temperature readout also did not work, and they normally work in KOEO mode. All the Key off elements worked: headlights, ARB compressor, electric fan.

I checked all fuses, and all were good. I looked for fusable links and didn't find any. I checked all the grounds I could find and found nothing.

Again, just the Key On / Engine OFF bits are not working, and the engine cranks just fine.

I'm not an electrical-savvy sort, so I have zero idea what could be going on. Oh, and just to be safe, I changed the ignition switch as well - to no avail.

 

[duncanrm]

I would check for continuity between the alternator output post and the battery positive terminal.. this will determine if there's a fusible link thats blown. In this situation, a test lamp with an incandescent globe is the tool to use.. put the test lamp clip on Negative, then touch the output post of the alternator with the business-end of the Test Lamp and see if the lamp lights up. Whilst you've got your test lamp out, I'd turn the ignition key on and check for +ve on both sides of each fuse (no need to remove them, you can probe them whilst still installed).

 

[Rumblefrog]

I would check for continuity between the alternator output post and the battery positive terminal.. this will determine if there's a fusible link thats blown. In this situation, a test lamp with an incandescent globe is the tool to use.. put the test lamp clip on Negative, then touch the output post of the alternator with the business-end of the Test Lamp and see if the lamp lights up. Whilst you've got your test lamp out, I'd turn the ignition key on and check for +ve on both sides of each fuse (no need to remove them, you can probe them whilst still installed).

Many thanks for the input. I will definitely try this.

 

[Rumblefrog]

I would check for continuity between the alternator output post and the battery positive terminal.. this will determine if there's a fusible link thats blown. In this situation, a test lamp with an incandescent globe is the tool to use.. put the test lamp clip on Negative, then touch the output post of the alternator with the business-end of the Test Lamp and see if the lamp lights up. Whilst you've got your test lamp out, I'd turn the ignition key on and check for +ve on both sides of each fuse (no need to remove them, you can probe them whilst still installed).

Checked continuity between alternator output post and battery positive, and I have continuity.

 

[erics]

Checked continuity between alternator output post and battery positive, and I have continuity.

a couple things stand out to me... first, with a non-oem install of a 1HDT in a 60 god only knows how electrical was integrated between the stock 60 harness/control systems and the 1HDT engine/charging and glow systems. Second, you mention you have two batteries so that could mean even more custom (ranging from good to complete hack) integration of either 24 volt setup with 12 volt takeoff or isolate-able engine/starting vs house/accessory batteries.

Based on what you've described I'd start with tracing where the connection to the fuel solenoid is coming from and determine why it is not live with key on. If you fix that you can then drive, plus will likely learn more toward fixing the rest. Second task would be tracing feed to the glow bus bar... I would guess it is fed off of good sized solenoid activated by a manual wilson switch.

 

[Rumblefrog]

a couple things stand out to me... first, with a non-oem install of a 1HDT in a 60 god only knows how electrical was integrated between the stock 60 harness/control systems and the 1HDT engine/charging and glow systems. Second, you mention you have two batteries so that could mean even more custom (ranging from good to complete hack) integration of either 24 volt setup with 12 volt takeoff or isolate-able engine/starting vs house/accessory batteries.

Based on what you've described I'd start with tracing where the connection to the fuel solenoid is coming from and determine why it is not live with key on. If you fix that you can then drive, plus will likely learn more toward fixing the rest. Second task would be tracing feed to the glow bus bar... I would guess it is fed off of good sized solenoid activated by a manual wilson switch.

Thanks for the input! The glow plugs work off a manual push-button. With Key on, I hold the button in for ten seconds and then hit the starter - usually fires up instantly. I will see if I can trace the fuel solenoid and the glow plug bus-bar.