Blowing the main fusible link
 

My 87 TII was running (rough, but running). I shut it off, came back to it about 3 weeks later, and no power in the car anywhere. I discovered the 80 amp fusible link was blown. Ordered new links, replaced, and as soon as the power is connected "POP" she blows again. Any ideas?

The car is running off of a Microtech LT8s, with a battery (full charge, as it stays on a trickle charge) relocation to the rear. I also have a power distribution block and will be diagnosing each connection over the next few days. I just don't get it. The car was running and now it goes to something like this. After 23 of these cars, I should have learned my lesson....buy nice complete ones and quit building them from scratch. The things you do for your kids though!

Chime in with any suggestions.

JTB

If it still has the Top mount IC there is a chance that it will hit the 12v + screw on the alternator and pop the fuse.

What up Super Dave?

I'm running a FMIC, FD UIM/TB and what looks like a S5 or FD alternator. I have yet to find an exact picture describing what alternator I have. Regardless, the lug isn't touching anything and since I have been wiring up the Microtech, I have had a rubber cap and e-tape wrapped over the lug just ensure no contact while that is hot.

It just bothers me that the car was running, I shut it off and leave it stored for the harsh winter, come back and now it is popping the big link. No indication there have been mice or anything else....just no power.

i would just unplug all the big things, put a new fuse in, hook up the battery, then start reconnecting stuff one at a time and see if you can pin-point the issue. or just get the biggest fuse you can possibly jam in there and run it ;) just kidding

That's my plan barkz. I'm just having to finish up this café build of an old school GS1000. Hopefully have time this weekend for my son to do just as you describe.

The Main fuse takes voltage from the charging system and sends it to the ignition switch and the two largest amped fuses at the top of the interior fusebox, which would be the defroster and heater fuses. Also, when the Black cable exits the engine fusebox it drops downward about a foot below the fusebox and mates w/another like colored cable. You could try unplugging this connector to see if you could at least indicate that the part of the circuit leading up to the connector is good. If so, then you could then focus on the segment after the connector.

I hear what you saying Satch. When I relocated the battery to the rear, I replaced the entire positive cable with a two gauge cable then made sure my grounds were clean and good.

I will check those fuses under the dash. I had thought about the hvac stuff because mine doesn't work properly, as in doesn't switch from cool to heat. I wondered if maybe something in the control unit is shorting now. I will probably unplug it just to be safe.

Off topic but, i too have a gs cafe project. 81 gs550. 1000 is a little big for cafe i think lol

It is a little big but I'm not doing a full cafe on this one. Finished the carbs and exhaust tonight. Still have club bars, grips, bar end mirrors, wheels to refinish, replace tires and brakes, and paint. This one is too clean to really go all out. I will flip this one soon and then I have a GS850 coming right behind it. Hopefully flip that one quickly and move on to a V65 Magna I've been eyeballing.

I would say the HVAC being messed up would blow one of the smaller fuses in the interior and stop there.

Is there a way of disconnecting the large wire(s) you ran to the back (for the battery) and temporarily connect the battery up front to remove the large wire(s) from the equation?

Yep, I can do that. My plan this weekend is to disconnect all the positive wires going into the distribution block, make sure the battery is hot, then start plugging each wire back in to see what pops the link.

a more effective method would be to use a multimeter, checking continuity to ground

I checked the continuity...way off. Did another voltage reading and noticed it read negative 12.xx volts. To ensure this wasn't my meter, I checked two other of my vehicles and all read the correct positive number.

Contacted a friend of mine that does electrical work and he says the negative volt reading indicates the car is a positive ground right now. More than likely, it is also pulling 120 or more volts to pop an 80 amp link so quickly.

Any ideas on what could be causing the positive grounding issue? I plan to check some stuff this afternoon.

another backwards ass battery? lol what are you guys doing?

Well, shizzzzzzzzzzzzzz. I had my son disconnect the battery terminals and check the battery. She reversed polarity.

Barkz, my case is not a backwards battery. She discharged and when I recharged the battery, somehow or another the battery reversed. I've been doing this way to long to get battery cables switched. Been working on these cars since 86. First time I have ever had a battery reverse polarity. Now, my hopes are in the fact that the link popped so quickly that it saved my Microtech. I shall know soon.

JTB

i meant polarity, this is the second thread in a week that talked about this lol. the other thread ended in him replacing the ECU

Don't say that man! I really don't need to be looking at buying another ECU right now. Been dumping money into this GS1000 and bought half of a Wagyu processed cow for the freezer. I'm hoping the link popping saved it.

lol well i hope thats not the case here

Woohoo! Good news to report.

As you see in post #15, I discovered that the battery has switched polarity and was positive grounding. Replaced the battery this evening, replaced the blown 80amp link, car came to life. But no Microtech. Did a volt check on the wiring to the Microtech, no juice. Found the inline 15amp fuse that I put in there (actually remembering to do smart things like this as I get older), fuse blown, replaced with new one, voila...Microtech is alive. Car is alive and we are back to my tuning issues now. I will deal with this more later in the week.

Just glad to know everything is good to go. I'll sleep better tonight.

Thanks for everyone's input.

JTB