JDMClassic Posted August 30, 2014 Report Share Posted August 30, 2014 Hello ratsun community. This is my situation. I just bought a 1974 Datsun 620 from a guy up in LA. After purchasing it I drove it back home in San Diego. I noticed the that "charge" indicator was illuminated on the instrument panel. The dude I bought it from said his mechanic said it was normal. Everything was running smoothly with my truck until about 2 exits away from my house and 150+ miles later it died on me. About 15mins earlier I noticed that my lights were getting dimmer and my radio would turn on and off. Also the "charge" light on the instrument panel went away. That's when it died. I pulled over and tried to restart it and nothing was turning on, it wouldn't crank neither, completely dead. So I went to my house and grab some jumper cables to see if my battery was bad and when I connected the positive side after the negative I seen smoke! I immediately unhooked the cables and investigated where the smoke was coming from. It looks like the smoke was coming from the hotside off the alternator. It's the wire bottom of the yellow wires My question is what can I do to fix this issue. Do you think it's my battery? (Previous owner said he replaced The battery few months ago) Issue with my alternator? (Looks brand new!) The type of wire connecting from the alternator to the battery? (I think my truck was using a 4 gage wire.) What else should I check for since that positive wire was fried? I hope I didn't fry anything else! Quote Link to comment
flatcat19 Posted August 30, 2014 Report Share Posted August 30, 2014 IR alternator in an ER setup? 1 Quote Link to comment
JDMClassic Posted August 30, 2014 Author Report Share Posted August 30, 2014 IR alternator in an ER setup? How would i know if I have a external or internal? Quote Link to comment
cr83 Posted August 30, 2014 Report Share Posted August 30, 2014 make sure that huge positive cable end on the battery post isn't touching the hood Quote Link to comment
DanielC Posted August 30, 2014 Report Share Posted August 30, 2014 The charge light being on, when the engine is running, is not normal. A 1974 620 had an externally regulated alternator, when it left the factory, I believe. Internally regulated alternators came later. Alternators have a set of six diodes in them, because an alternator makes AC electricity, and the diodes convert the AC electricity to DC electricity. If the diodes go bad, short out, that will cause the positive connection on the alternator to connect to ground. Take the alternator out. Look at the back of the alternator, by the two small terminals that are in a "T" orientation. there should be two other letters by that connection. If you have "F", and "N", it is an externally regulated alternator. "S" and "L" is an internally regulated alternator. When the alternator is out have it tested at an auto parts store. Quote Link to comment
datzenmike Posted August 30, 2014 Report Share Posted August 30, 2014 The charge light being on, when the engine is running, is not normal. Truer words were never spoken. The charge lamp is wired to the battery on one side and the alternator output on the other. As long as the charge voltage is close to the battery voltage the lamp cannot be seen. If the alternator fails to charge, power from the battery flows through the lamp to the alternator, lighting it. That wire that is burnt should not have happened. The alternator output has to flow through a fusible link in order to get to the battery to charge it. Excessive charge current from the alternator would, or should, blow the fusible link first. The fusible link will prevent what has happened here. That wire may have melted several wire in that harness together causing an unbelievable mess to sort out. There is some home made wiring there between the alternator and the positive battery terminal. I would remove all the electrical tape from it and separate the wires. I also do not see the fusible link there. The charge wire from the alternator is a large White/Red stripe wire. Quote Link to comment
JDMClassic Posted August 30, 2014 Author Report Share Posted August 30, 2014 Truer words were never spoken. The charge lamp is wired to the battery on one side and the alternator output on the other. As long as the charge voltage is close to the battery voltage the lamp cannot be seen. If the alternator fails to charge, power from the battery flows through the lamp to the alternator, lighting it. That wire that is burnt should not have happened. The alternator output has to flow through a fusible link in order to get to the battery to charge it. Excessive charge current from the alternator would, or should, blow the fusible link first. The fusible link will prevent what has happened here. That wire may have melted several wire in that harness together causing an unbelievable mess to sort out. There is some home made wiring there between the alternator and the positive battery terminal. I would remove all the electrical tape from it and separate the wires. I also do not see the fusible link there. The charge wire from the alternator is a large White/Red stripe wire. Yes I see the white/red stripe wire and as I was tracing it it seems like the other wires around it are ok and have no been burnt.. I'm planing on replacing the entire length of the wire but I don't know where it leads to. I thought it lead to the positive side of the battery but it's branching off to some where else... Quote Link to comment
wayno Posted August 30, 2014 Report Share Posted August 30, 2014 You likely would have made it home if you had not had to use the headlights. I am not saying you did this, I am just asking to make sure, are you sure you connected the positive side of the jumper cable to the positive side of the dead battery? Quote Link to comment
JDMClassic Posted August 30, 2014 Author Report Share Posted August 30, 2014 The charge light being on, when the engine is running, is not normal. A 1974 620 had an externally regulated alternator, when it left the factory, I believe. Internally regulated alternators came later. Alternators have a set of six diodes in them, because an alternator makes AC electricity, and the diodes convert the AC electricity to DC electricity. If the diodes go bad, short out, that will cause the positive connection on the alternator to connect to ground. Take the alternator out. Look at the back of the alternator, by the two small terminals that are in a "T" orientation. there should be two other letters by that connection. If you have "F", and "N", it is an externally regulated alternator. "S" and "L" is an internally regulated alternator. When the alternator is out have it tested at an auto parts store. My engine is an L20b engine swap, would have any effect on what alternator I should have? Or whether or not have an internal or external regulator? Quote Link to comment
JDMClassic Posted August 30, 2014 Author Report Share Posted August 30, 2014 You likely would have made it home if you had not had to use the headlights. I am not saying you did this, I am just asking to make sure, are you sure you connected the positive side of the jumper cable to the positive side of the dead battery? Yea I was thinking the same, I half way on the trip back home I switched to high beams for more light. And no I'm sure I did the jumper cables correctly Quote Link to comment
datzenmike Posted August 30, 2014 Report Share Posted August 30, 2014 The above.... :thumbup: Also if the melting is just in the area shown, it's possible the wire and the lug is not making a good solid connection to the alternator terminal. Any resistance will generate heat. Take a look at the blue coating on the copper. That's copper sulphate or normal copper corrosion like a green penny. The wire is definitely corroded to begin with. My engine is an L20b engine swap, would have any effect on what alternator I should have? Or whether or not have an internal or external regulator? The L20B engine used internal and external regulated alternators depending on the year of the engine. Normally it would be easiest to just keep the 521 alternator. It may have either. Someone suggested removing the alternator and looking for the letters on the double plug to identify it. Quote Link to comment
JDMClassic Posted August 30, 2014 Author Report Share Posted August 30, 2014 The above.... :thumbup: Also if the melting is just in the area shown, it's possible the wire and the lug is not making a good solid connection to the alternator terminal. Any resistance will generate heat. Take a look at the blue coating on the copper. That's copper sulphate or normal copper corrosion like a green penny. The wire is definitely corroded to begin with. The L20B engine used internal and external regulated alternators depending on the year of the engine. Normally it would be easiest to just keep the 521 alternator. It may have either. Someone suggested removing the alternator and looking for the letters on the double plug to identify it. Mike you might be right! As I was unbolting the hot wire from the alternator it was loose! BUT do you think the heat of the wire could of caused it to come loose like that?? Should I replace the entire wire? I was tracing it and branches off deeper into the engine bay. Or should I just cut and replace a section of it? And I forgot to add that as I was unbolting the hot wire. The actual bolt foundation on the alternator is loose... Could my alternator be fried? Quote Link to comment
wayno Posted August 30, 2014 Report Share Posted August 30, 2014 That wire being loose can also make the alt light come on. Quote Link to comment
datzenmike Posted August 30, 2014 Report Share Posted August 30, 2014 Heat won't cause looseness but looseness can definitely cause heat. And the alt light to be on, and the battery not to charge. You could probably getaway with securely taping that bare wire up. Better would be some heat shrink tubing. If that lug is burnt maybe trim the wire back and crimp another on. make sure it is tight on the alternator but don't strip the threads. Quote Link to comment
JDMClassic Posted August 30, 2014 Author Report Share Posted August 30, 2014 Took the alternator out and I'm about to head to auto zone to have it checked out. What alternator should I get? Here's a picture of the alternator hotwire bolt I was talking about on the hitachi. Quote Link to comment
wayno Posted August 30, 2014 Report Share Posted August 30, 2014 Looks like it has been loose for a while, it would not surprise me if the alt. was still good, but that wire mount stud is looking ugly. According to Daniel that is an internally regulated alt. 1 Quote Link to comment
banzai510(hainz) Posted August 30, 2014 Report Share Posted August 30, 2014 look to see if you have a external volt reg. if yes then get the alternator for that year vehicle. If Volt reg plug has been modified by adding 2 jumper wires then you kow the alternator is most likly a internal unit. Yo me it look like a external type alter as i has the gage in back But Im only guess as my extarnat gage type atre revovable your is fixed with the case but same size out as yours. This BELOW comment is very tru is you have a hight resisitive short which can get hot. maybe trim insulation back and clean the copper(vinagar? _ and make a splice to the + side alt. Maybe use a red wire to know thats a Positive. I think your fine just fix that first but ck to dee if you have a External voolt reg. should be on Pass side wheel well area Also if the melting is just in the area shown, it's possible the wire and the lug is not making a good solid connection to the alternator terminal. Any resistance will generate heat. Take a look at the blue coating on the copper. That's copper sulphate or normal copper corrosion like a green penny. The wire is definitely corroded to begin with. They guy who said light on is Normal? WTF!!!!!!!!!!!! Quote Link to comment
JDMClassic Posted August 30, 2014 Author Report Share Posted August 30, 2014 look to see if you have a external volt reg. if yes then get the alternator for that year vehicle. If Volt reg plug has been modified by adding 2 jumper wires then you kow the alternator is most likly a internal unit. Yo me it look like a external type alter as i has the gage in back But Im only guess as my extarnat gage type atre revovable your is fixed with the case but same size out as yours. This BELOW comment is very tru is you have a hight resisitive short which can get hot. maybe trim insulation back and clean the copper(vinagar? _ and make a splice to the + side alt. Maybe use a red wire to know thats a Positive. I think your fine just fix that first but ck to dee if you have a External voolt reg. should be on Pass side wheel well area Also if the melting is just in the area shown, it's possible the wire and the lug is not making a good solid connection to the alternator terminal. Any resistance will generate heat. Take a look at the blue coating on the copper. That's copper sulphate or normal copper corrosion like a green penny. The wire is definitely corroded to begin with. They guy who said light on is Normal? WTF!!!!!!!!!!!! Do you have a picture of the voltage reg? Quote Link to comment
JDMClassic Posted August 30, 2014 Author Report Share Posted August 30, 2014 Should I upgrade to a higher voltage alternator? Is there a risk over over powering it? Quote Link to comment
JDMClassic Posted August 30, 2014 Author Report Share Posted August 30, 2014 So I just got back from Autozone and they told me that my alternator is bad... So it looks like they don't sale wire for the hotside of the alternator that burnt off...SMH GOing to pep boys to see if they can help me Quote Link to comment
datzenmike Posted August 30, 2014 Report Share Posted August 30, 2014 Took the alternator out and I'm about to head to auto zone to have it checked out. What alternator should I get? Here's a picture of the alternator hotwire bolt I was talking about on the hitachi. This was already answered... Take the alternator out. Look at the back of the alternator, by the two small terminals that are in a "T" orientation. there should be two other letters by that connection. If you have "F", and "N", it is an externally regulated alternator. "S" and "L" is an internally regulated alternator. When the alternator is out have it tested at an auto parts store. Sometimes the test is bad. I would put it back in, charge up the battery and see!!! Should I upgrade to a higher voltage alternator? Is there a risk over over powering it? You could put in a 1,000 amp alternator but it will only charge the battery at the same rate as a 35 amp. Fourteen volts is fourteen volts. The truck uses a 35 amp alternator because it's a smaller diameter and clears the idler arm and rad hose better. Higher output alternators tend to be larger and don't fit well. If your truck does not have fog lights, halogen head lights, big stereo amp the 35 amp is enough. 1 Quote Link to comment
banzai510(hainz) Posted August 30, 2014 Report Share Posted August 30, 2014 So it looks like they don't sale wire for the hotside of the alternator that burnt off...SMH your going to have to make this wire and splice your self. you can make a slip/turn lock type wire splice(insulated of coarse) . have a female on the wire side and a male pin on the + alt side that is alreadey on the alt. So later if you change your alt just twist the plus side off insteade of using a 8mm nut wrench. as mike said the 35amp fits perfect. then buy this and you can tell when you load it down. Trust it it works if you cig light works. Ps ck your fuses also You might have popped one or should have. But soemtimes the alt wire will pop before the fuse if weak. (as mine did when I hit my high beams) lost all power as it was the feed wire from starter lug to fuse box Quote Link to comment
JDMClassic Posted August 30, 2014 Author Report Share Posted August 30, 2014 This was already answered... Sometimes the test is bad. I would put it back in, charge up the battery and see!!! You could put in a 1,000 amp alternator but it will only charge the battery at the same rate as a 35 amp. Fourteen volts is fourteen volts. The truck uses a 35 amp alternator because it's a smaller diameter and clears the idler arm and rad hose better. Higher output alternators tend to be larger and don't fit well. If your truck does not have fog lights, halogen head lights, big stereo amp the 35 amp is enough. When i went to autozone they told me that the stock alternator had an external regulator. But what I thought I had an internal... Quote Link to comment
JDMClassic Posted August 30, 2014 Author Report Share Posted August 30, 2014 So it looks like they don't sale wire for the hotside of the alternator that burnt off...SMH your going to have to make this wire and splice your self. you can make a slip/turn lock type wire splice(insulated of coarse) . have a female on the wire side and a male pin on the + alt side that is alreadey on the alt. So later if you change your alt just twist the plus side off insteade of using a 8mm nut wrench. as mike said the 35amp fits perfect. then buy this and you can tell when you load it down. Trust it it works if you cig light works. Ps ck your fuses also You might have popped one or should have. But soemtimes the alt wire will pop before the fuse if weak. (as mine did when I hit my high beams) lost all power as it was the feed wire from starter lug to fuse box Will do! I'll check the fuses right now Quote Link to comment
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