IbanezDan51 Posted November 13, 2013 Share Posted November 13, 2013 Wiring up my LS at the moment and noticed that the wiring from the alternator first goes to the ammeter then to the starter + post. Has anyone found the need to upgrade the gauge wire as the stock Datsun wire would have been fine for a 45-50 amp alternator back in the day but with a newer alternator it might be too much? I might be looking at this totally wrong though... Cheers, Dan Quote Link to comment Share on other sites More sharing options...
wfritts911 Posted November 13, 2013 Share Posted November 13, 2013 The main power wire for the alternator should just go straight to the battery/starter post. The volt meter can be hooked up to any power source. The LS1 alternator plug is a 1 wire plug that goes to the ECM on 99+ LS1's, or goes to an ignition power with an inline resistor on 98 models. I don't have the stock Datsun voltmeter anymore, but when I did, the alternator wiring never even got close to it. -Will Quote Link to comment Share on other sites More sharing options...
IbanezDan51 Posted November 13, 2013 Author Share Posted November 13, 2013 The main power wire for the alternator should just go straight to the battery/starter post. The volt meter can be hooked up to any power source. The LS1 alternator plug is a 1 wire plug that goes to the ECM on 99+ LS1's, or goes to an ignition power with an inline resistor on 98 models. I don't have the stock Datsun voltmeter anymore, but when I did, the alternator wiring never even got close to it. -Will I have kept my stock wiring loom and ammeter gauge - it doesn't have a voltmeter. The wiring goes from the alternator to the fuse board, then to the ammeter and from this back in to the loom and to the starter. Quote Link to comment Share on other sites More sharing options...
wfritts911 Posted November 13, 2013 Share Posted November 13, 2013 Oh...i just assumed you were calling an volt meter and ammeter, guess the jokes on me. Never seen a car with an ammeter, but then again I don't own an early S30 which is what they apparently came in. From a brief read, it looks like wiring it like factory makes the main power source from the alternator run through the dash harness and to the gauge. Not a good idea IMHO. Upgrading the wiring never hurt considering its 40 years old. -Will Quote Link to comment Share on other sites More sharing options...
IbanezDan51 Posted November 13, 2013 Author Share Posted November 13, 2013 It would seem upgrading the wiring would be useless. There is a shunt resistor somewhere in the line or on the ammeter which will just blow when I try to run it in its current state. Need a later model voltmeter it would seem! Dan Quote Link to comment Share on other sites More sharing options...
zdlite Posted November 19, 2013 Share Posted November 19, 2013 (edited) I'm not sure what year your car is or if it differs from my early 240Z. But the way they have the ammeter wired the size of the alternator shouldn't matter. On my car the alternator wire goes to the left half of the fuse box. The majority of the electrical loads are fed off that side. From there a wire goes up through the ammeter and back to the right side of the fuse box. The right side of the fuse box powers stuff like emergency flashers / horn as well as the battery. So with the motor running the ammeter is only showing the current charging the battery and when the motor is off is measures battery current powering the accessories. The battery won’t draw any more current just because the alternator is bigger. Having said all that the smartest thing you can do is swap out the ammeter for a voltmeter. Easy to do. Basically just jumper the two big wires at the back of the ammeter then run a single voltage sensing wire to the voltmeter. I went a step further and added a junction box up near the radiator. I run the alternator to that. The junction box has 4 fuse circuits. One I run to the radiator fan relays, the second I run to the battery and the third I run to the fuse box. I took both wires from the fuse box (the old one that use to go to the alternator and the one that went to the battery) and spliced them together. That way I have two large gauge wires feeding the fuse box with zero battery current. Also running a wire straight from the alternator to the battery can overcharge the battery if you’re not lucky. Better to run it to a junction or starter lug then feed the battery off that. Here is a good link describing why this is beneficial http://www.madelectrical.com/electricaltech/remotevoltagesensing.shtml Another advantage of a voltmeter is you get an idiot light for the charging ciruit. If you hook your alternator sense wire up to that you won't need the resistor. By the way, I didn't think Datsun used shunt resistors the way Chevy did. On my early 240 it is a straight ammeter measuring current to the battery. Edited November 19, 2013 by zdlite Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.