stav2201 Posted November 17, 2011 Share Posted November 17, 2011 Im blowing the fusible links on my 1975 280z that run from the ignition switch to the starter motor, This means that an electrical device called a "Shunt" is in between it. I have replaced my battery, alternator, and starter and all my fuses still go out. Im wondering if this Shunt could be the issue. If so, are there any ways to bypass this device or will i have to replace it. Here is a picture of the electrical device im talking about Quote Link to comment Share on other sites More sharing options...
stav2201 Posted November 17, 2011 Author Share Posted November 17, 2011 Im blowing the fusible links on my 1975 280z that run from the ignition switch to the starter motor, This means that an electrical device called a "Shunt" is in between it. I have replaced my battery, alternator, and starter and all my fuses still go out. Im wondering if this Shunt could be the issue. If so, are there any ways to bypass this device or will i have to replace it. Here is a picture of the electrical device im talking about forgot to mention that im using a 280zx alternator now Quote Link to comment Share on other sites More sharing options...
RB26powered74zcar Posted November 17, 2011 Share Posted November 17, 2011 Question: Is that red cable at the top right in your picture touching / grounding to body metal? Let me know if you determine you need another shunt. I believe I have a spare... Quote Link to comment Share on other sites More sharing options...
stav2201 Posted November 17, 2011 Author Share Posted November 17, 2011 Question: Is that red cable at the top right in your picture touching / grounding to body metal? Let me know if you determine you need another shunt. I believe I have a spare... Nope, this is a picture i got from online for reference. I'm wondering if anyone knows if these even go out. Quote Link to comment Share on other sites More sharing options...
NewZed Posted November 17, 2011 Share Posted November 17, 2011 Did things work right before the ZX alternator or is this problem coincident with the ZX alternator "upgrade"? Which of the two links blow? When do(es) they(it) blow - when the battery is connected, when the key is turned to On, or when the key is turned to Start? Have you tried disconnecting the shunt and testing each terminal for a short to ground? Test each connector for a direct short to ground also. There's not much to the shunt, it just directs a portion of the charging current through the ammeter. It does have connections to the VR though, so if you just modified the wiring for the ZX alternator, you might have misplaced a wire. I would guess one of the white ones. There's a good 1975 wiring diagram on http://www.atlanticz.ca/zclub/techtips/electrical.htm Quote Link to comment Share on other sites More sharing options...
stav2201 Posted November 18, 2011 Author Share Posted November 18, 2011 Did things work right before the ZX alternator or is this problem coincident with the ZX alternator "upgrade"? Which of the two links blow? When do(es) they(it) blow - when the battery is connected, when the key is turned to On, or when the key is turned to Start? Have you tried disconnecting the shunt and testing each terminal for a short to ground? Test each connector for a direct short to ground also. There's not much to the shunt, it just directs a portion of the charging current through the ammeter. It does have connections to the VR though, so if you just modified the wiring for the ZX alternator, you might have misplaced a wire. I would guess one of the white ones. There's a good 1975 wiring diagram on http://www.atlanticz.ca/zclub/techtips/electrical.htm I upgraded the alternator 1 year ago when i was running NA. Ive recently upgraded to a turbo set up from an 85 300zx ecu. The black 80 amp fuse was the first to go out 1-2 weeks ago in which case i replaced the alternator. It worked fine for a week,but a week later i noticed it was sputtering a little while holding a constant idle and under load the engine would lose power completely for a second and then run normal again. I opened the shunt and replaced the 2amp fuse since it was out, my guess is a small Wht/red wire that connects the ignition switch is grounded under the dash. It is a 16 gauge wire that connects to the c-5 green coupler under the passenger side. It blows my 40 amp fusible link every time i turn the key to the ACC spot. Quote Link to comment Share on other sites More sharing options...
NewZed Posted November 18, 2011 Share Posted November 18, 2011 Sounds like you know what you're doing. You might try leaving the battery disconnected, and the shunt, and the fusible link, turn the key to ACC and check the various connectors for what portion of the circuit the short is in. Isolate it to a smaller area. Check the shunt for an internal short, and short to the housing also. If you're blowing a 40 amp link, it would be a low resistance short. That's a lot of current. Something might have melted when the 80 amp link blew before. Quote Link to comment Share on other sites More sharing options...
stav2201 Posted November 18, 2011 Author Share Posted November 18, 2011 Sounds like you know what you're doing. You might try leaving the battery disconnected, and the shunt, and the fusible link, turn the key to ACC and check the various connectors for what portion of the circuit the short is in. Isolate it to a smaller area. Check the shunt for an internal short, and short to the housing also. If you're blowing a 40 amp link, it would be a low resistance short. That's a lot of current. Something might have melted when the 80 amp link blew before. So what your suggesting is its one of the red/wht wires in between the ignition switch, im not sure how to narrow it down to a specific area if that is what you mean. I was going to tear out the entire wire harness and unwrap it to see what i could find personally. Quote Link to comment Share on other sites More sharing options...
NewZed Posted November 18, 2011 Share Posted November 18, 2011 Disconnect everything from the switch to the starter and measure resistance to ground from every pin in the various connectors with an ohm-meter. If you find the pin or connection with zero resistance, then you'll know that anything connected to that pin should be looked at (unless the pin is supposed to be to ground, of course - have the wiring diagram handy). Then you can focus on the path that that one pin uses instead of worrying about everything from the battery to the starter, plus any branches. It really doesn't take much time, and when you find the connection that is grounded, but shouldn't be, you'll know you're on the right "path". It's just a meter-based method, using the wiring diagram, versus the eyeball technique. You'll probably find the problem with a lot less effort than pulling out the entire harness. Of course, tearing things apart is part of the fun. Quote Link to comment Share on other sites More sharing options...
stav2201 Posted November 18, 2011 Author Share Posted November 18, 2011 I tore out the entire harness under the dash and only found one of the Wht/Red cables on the C5 coupler slightly damages at the pin. This is the wht/red wire that connects straight to the ignition switch, not sure if thats enough to blow fuses though since the only thing it would be in contact with is the plastic from the connector Quote Link to comment Share on other sites More sharing options...
stav2201 Posted November 30, 2011 Author Share Posted November 30, 2011 It seems my issue is bigger than i thought. My battery is no longer getting charged when running the engine, i swapped over to a 60amp self regulated alternator and removed the external regulator. When the car is idling im putting out 16 volts from the alternator and not getting any power to the battery(Ive replaced the alternator 2 times so far as well). Seeing as how my entire wire harness is cut and spliced from the previous owner i want to replace it all, im wondering if you can use a 1978 280z dashboard wire harness and charging system harness on a 75? Quote Link to comment Share on other sites More sharing options...
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