2H Voltage Regulator up in smoke!

[adrianwho]

Hoping to get some advice from fellow mudder's on here who may have had similar issues. Haven't been able to drive the truck for the past two weeks and really wanna get it running!

Truck in question is a 1989 HJ60 RHD 24V with the 2H and external voltage regulator (27700-57090).

Went to start it up a couple weeks ago, and on start up I heard the external voltage regulator blow and a bunch of smoke came from it. The wires melted and with the key on (and external VR disconnected) the EDIC/fuel control relay started clicking and doing the funky chicken. Not sure if the VR problem is related, but I pulled the relay and found a bit of corrosion on the board. So it seems my fuel control relay went out at the same time, but could just be coincidence.

Fast forward to today, I purchased a new OEM external VR (27700-57080) and installed it. Turned the key to on to test, and the fuel plug relay stopped doing the funky chicken (but didn't move the edic rod to start position and was stuck in off position). I then popped the edic arm off so it went into start, and unplugged the fuel control relay so I could see if the new VR would start the truck.

Once again on start up, the external VR blew up in smoke within a second or two of trying to start the truck. Pretty bummed out at wasting $$$ and blowing another VR... Decided to remove the VR, and see if I could at least start the truck. With 3 start up attempts, each attempt I heard the starter turn over for only a second at most. On the third attempt, I saw some smoke come from the starter area and decided to give it a rest.

Things to note:
-Before I installed the new VR I checked fusible links, batteries, ground cables and all tested good with a multimeter
-After seeing smoke from the starter, I checked and couldn't find any problems with the starter wiring (checked ohms, voltage and visually looked ok). The starter itself is super crusty/old so might need to pull it off to test
-Alternator wires visually look fine and have strong connections
-Checked starter relay, ignition barrel, seem fine

What else should I test?

Right now my best bet from the advice of a friend is to trace the burnt wiring from the external VR back through the harness it's connected to. Theory being that the most burnt wires will be a good indicator of what probably has a short.

Curious if anyone else on here has any ideas? Pretty damn stumped with this one!

 

[duncanrm]

Things to note:
-Before I installed the new VR I checked fusible links, batteries, ground cables and all tested good with a multimeter

It's pretty much impossible to conclusively check the things you've listed above with a multimeter, they flow negligible current and are very deceiving in an automotive environment, for example a bad connection can show perfect voltage (or continuity) right up until you ask it to do actual work. My diagnostic weapon of choice on an old Landcruiser is almost always a Test Lamp with an incandescent bulb ("low impedance" device)

I am suspicious of:

• The engine or body earthing (ground) being problematic and alternative earth return pathways being found, and smoking out.
• Your Glow System earthing out.

If this were my vehicle. I would:

• Visually inspect the glow system - remove the glow rail and check for a path to earth through the isolating posts and various links etc (with a test lamp)
• Remake your engine and body earths - new cables, wirewheel on the attachment points first, there's no downside to adding additional grounding points either
• Remove the starter and inspect/refurbish the solenoid
• Replace the starter high current lead with a fresh one (again, wirewheel the starter post and clamp nut/washer)
• Remake your battery terminals if you're not happy with them (send photo for opinion)
• Strip back the loom where you've seen burnt wires and remediate
• Remove the alternator (taking care to isolate the B+ wire so it doesn't short out)
• Get the vehicle starting/running again without worrying about the alternator at this point
• Convert the vehicle to a new internally regulated alternator and run a brand new B+ wire across to the battery through a Midi Fuse of appropriate size (wiring changes are well documented)
• Confirm vehicle charging fine
• Start looking at the Fuel Control Relay issue (or just convert to a Stop Cable) . There are good aftermarket version of the FCR now that may be an option (Hendra Motors, Australia)

 

[adrianwho]

Hey Duncan, appreciate the notes and your time writing that out! Definitely gonna go over everything you listed.

Didn't know that about the multimeter. I retested fusible links and grounds with test lamp, and all checked out fine. I recently remade a fusible link and new battery terminals/connections and will continue to replace all of the grounds with new heavy gauge wire.

Still have to test the glow system (I'm not as familiar and will have to do some reading before diving in) but I think you're onto something about a ground likely being the main problem.

Reinspecting the burnt up wiring on the external voltage regulator, the white wire with black stripe is the one that melted (on two regulators), which should be the ground wire E.

The L pin on the other side of the harness gave me a reading of 11.1V which seems strange. Should it not be 24V? According to the FSM, this goes to the charge warning light which hasn't been working on my truck for the past month. Bulb was burnt out when I inspected for the charge light in the dash, but the engine 15A fuse was fine. Will need to look more into this, but seems like there's a short there.

Reinspecting the alternator wires, I found some corrosion I missed on the first pass. Will clean up and inspect further with more patience and hopefully figure out what's going on with the wiring there too.

Still have a bunch of bullet points in your list to go through, but making good progress so I'm stoked.

Thanks again for the help.