srfjay Posted January 20, 2015 Report Share Posted January 20, 2015 I have a 1971 510, the wiring harness was pretty trashed when I got the car so just redoing it. Now from the diagrams it looks like the white/red wire goes to the charge light in the dash then to the green wire to the fuse box. If I am adding gauges and want to remove that dummy light can I just splice the white/red wire directly to the green wire? From the looks of the diagram it seems to be that way but just wanted to double check. Thanks guys. Quote Link to comment
DanielC Posted January 20, 2015 Report Share Posted January 20, 2015 No. the idiot light is used by the alternator to energize itself. The light may also act as a resistor, to lilit current flow to parts of the charging system. You might be able to connect the two wires together, and be OK, or not. if you keep the wiring stock, or as close to stock as you can, when future problems occur, other people her will be able to help you. If you deviate from stock, we have no idea of how it was done, and we cannot help you. You become that "previous owner" that hacked a wiring job. Quote Link to comment
DrRocks0 Posted January 20, 2015 Report Share Posted January 20, 2015 You need the dummy light. It grounds the rectifier in the alternator. Without it the car doesn't charge when you first start it up until you rev it then it starts charging at 15.2ish depending on the health of your alternator. Guess how I figured that one out.... :angel: Quote Link to comment
srfjay Posted January 20, 2015 Author Report Share Posted January 20, 2015 Interesting. Well I do understand keeping it stock is a good ideal but when I got the car the harness was already hacked. I am just trying to clean it up. I guess I will have to read up a little more on it. Since the cluster was already modified for the new gauges. Quote Link to comment
srfjay Posted January 20, 2015 Author Report Share Posted January 20, 2015 Another question, since I do need something between the wires. Would a simple resistor work in place of the bulb? Quote Link to comment
thisismatt Posted January 20, 2015 Report Share Posted January 20, 2015 Do not connect the wires together. This will be a short. Yes, a resistor will work, by why would you not want an indicator light? Because you have a voltage gauge? By the time you realize there is an issue and look at your voltage gauge it will probably be leaving you stranded. 1 Quote Link to comment
srfjay Posted January 20, 2015 Author Report Share Posted January 20, 2015 Yes a voltage gauge. And not that I don't want one just the stock cluster was having issues. And it had a clock so added a tachometer in its place. I could just add another bulb and install it someplace in the dash. Is the build used special in anyway? Or are the indicator bulbs all the same? Quote Link to comment
srfjay Posted January 20, 2015 Author Report Share Posted January 20, 2015 This kind of explains what I am doing. If I can just add in a indicator bulb that would be good Quote Link to comment
thisismatt Posted January 20, 2015 Report Share Posted January 20, 2015 12v, 1.5-3w incandescent bulb, or an LED will work as long as it has a resistor in parallel to provide the same function. Looks like you would have room on either lower corner of the tach. Quote Link to comment
srfjay Posted January 20, 2015 Author Report Share Posted January 20, 2015 http://www.amazon.com/12-Volt-LEDs-Internal-Resistor/dp/B00RRBWUMG/ref=sr_1_17?ie=UTF8&qid=1421784582&sr=8-17&keywords=12+volt+resistor&pebp=1421784600314&peasin=B00RRBWUMG Thanks for the help. And this has a built in resistor. That should work for the application correctly? Quote Link to comment
thisismatt Posted January 20, 2015 Report Share Posted January 20, 2015 I think that should work, unless 1kohm is too high to excite the alt. Someone correct me if I'm wrong. The positive side would need to be the one that goes to the ignition, while the negative goes to the L (lamp) circuit on the alternator, since the L acts as a ground until running. Quote Link to comment
srfjay Posted January 20, 2015 Author Report Share Posted January 20, 2015 Yeah that is what I am stuck on. Knowing the right resistance. Quote Link to comment
DanielC Posted January 20, 2015 Report Share Posted January 20, 2015 Lets see, 12 volts, 1.5 watts. Watts divided by volts equals amps. 1.5 watts /12 volts =.125 amps Volts divided by amps equals resistance. 12 volts / .125 = 96 ohms. A 100 ohm resistor would do it. You need a resistor that can dissipate 1.5 watts Quote Link to comment
srfjay Posted January 20, 2015 Author Report Share Posted January 20, 2015 Thank you guys for all he help. I am curious now. How does the stock charging indicator bulb controller the volts? From everything I see there is no stock resistor in place. It just goes white/red to bulb then to green. Quote Link to comment
srfjay Posted January 20, 2015 Author Report Share Posted January 20, 2015 So as it shows in the graphic it comes from the regulator straight to the bulb. So I am guessing the regulator is only putting out the 1.5 watts on the white/red wire? So I am curious why a resistor would need to be used now but not in its original form. Just trying to understand . I am no wiring expert. Quote Link to comment
DrRocks0 Posted January 20, 2015 Report Share Posted January 20, 2015 Well my car is a 1968 if that makes a difference. This diagram is from 1970. Quote Link to comment
DanielC Posted January 20, 2015 Report Share Posted January 20, 2015 This is kind of basic. There are usually four electrical connections to the externally regulated alternator on a Datsun. A ground. Main output. A field connection. A neutral connection. The field connection is the coil inside the alternator rotor. It is an electromagnet. No electricity, no magnetism. If you leave the field connected all the time, it will drain the battery in about 24 to 48 hours. When you turn the key on, switched ignition power is sent to the voltage regulator, to connect the field coil in the alternator to power. There is also a connection made in the voltage regulator that grounds the idiot light. When the alternator starts to make power the idiot light connection is broken, or switched off. Again, when the alternator is not working, the voltage regulator connects the idiot light to Ground. Take the light out, and connect the two wires together, and you create a short circuit to ground. If there is no voltage coming from the alternator, a relay connects 12 battery volts to the field coil of the alternator. As the alternator speeds up, and the battery gets charges again, the relay controlling the field coil switches a resistor on the voltage regulator into the field coil circuit. This cuts down the alternator output. If the voltage still continues to rise, the field coil will be completely disconnected. The voltage regulator needs the neutral connection. I am not sure why. If you convert to an internally regulated alternator, you have no voltage regulator. The alternator controls itself. It needs ignition switched power to the internal regulator, this power comes through the idiot light. Quote Link to comment
DanielC Posted January 20, 2015 Report Share Posted January 20, 2015 The regulator does not put out 1.5 watts to the charge light. The charge light is connected to battery power by the ignition switch. The voltage regulator grounds the charge light, when the alternator is not making power. That is what turns on the charge light. Quote Link to comment
srfjay Posted January 21, 2015 Author Report Share Posted January 21, 2015 Thanks danial c for the info. It really helps. One last question. If I just install the correct 1.5 watt led bulb were the stock bulb was why would I need the resistor ? Or is the resistor only needed if I use no bulb? What I am thinking of doing is white/red to negative on bulb then green to positive. If I do it this way no need for a resistor correct ? Since I am just switching out the stock bulb for a led. Quote Link to comment
DanielC Posted January 21, 2015 Report Share Posted January 21, 2015 Lets start with this. No led is correct in this circuit. This circuit was designed 45 years ago, when a normal incandescent lamp was all that was available. I am going to guess that a majority of 1970's Datsuns are still running around with the same lamp bulb in the instrument cluster for the "charge light" that they left the factory with. Quote Link to comment
srfjay Posted January 21, 2015 Author Report Share Posted January 21, 2015 Well it does not have to be led . I am just trying to figure out the best solution. This is the only step I am hung up on. I understand how the system works now just trying to figure out the best way around it. Quote Link to comment
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