TasoZ24 Posted January 13, 2015 Report Share Posted January 13, 2015 Terribly sorry to bring this up as I know its been discussed over and over, but I cant seem to find the answer to my problem. My 83 720 w/ Z24 has been not charging properly and the indicator never comes on. I have replaced the bulb and regrounded everything, traced wires and got voltage where it needs to be, still no light or proper charge. With truck at idle im getting steady 12.2 v at battery and only 11.5 at alt terminal and goes past 15 when revving, but sporadically jumps around high to low. The harness has been torn into a bunch and fusible links seem to be nonexistent. However im getting readings for volts where there should be while key in right position. Have gone through everything and cant figure this out. This is third alternator, first was super spent with bad bearings, second was in truck for two months. The blinker and taillights were the first to go, then radio, until finally dead battery in a carls jr drive thru. A new battery later im dead again in 70 miles. Got truck home to find my voltage is dropping while truck running and drains faster when revved. Got alt bench tested and passed. So I retrace wires, connections and check grounds. Then im up to where im at 12.2 idle and sporadic during rpms, exceeding 15. Got alt tested while truck, failed the regulator, so I got "new" warranty 60amp oriley special, and belt. Put it in at store and tested again with same results. So weird voltage and no charge light in dash is where im at. Thanks for any help whatsoever. 1 Quote Link to comment
thisismatt Posted January 13, 2015 Report Share Posted January 13, 2015 Are you sure that the S (sense) and L (lamp) terminals on the alt are connected correctly? S should go to hot, eg straight to battery or positive at starter. L connected to the charge lamp with the other side of charge lamp to switched ignition. 1 Quote Link to comment
TasoZ24 Posted January 13, 2015 Author Report Share Posted January 13, 2015 Wht/blu is on top going to autochoke. Bigger wht going to lamp. No light, new bulb. Goes to meter fuse? All new fuses regardless... 1 Quote Link to comment
TasoZ24 Posted January 13, 2015 Author Report Share Posted January 13, 2015 Reroute blu/wht(S) to constant hot? 1 Quote Link to comment
wayno Posted January 13, 2015 Report Share Posted January 13, 2015 Why would an alternator wire go to the auto choke??? 1 Quote Link to comment
TasoZ24 Posted January 13, 2015 Author Report Share Posted January 13, 2015 Electrical reasons just going by diagram. 1 Quote Link to comment
wayno Posted January 13, 2015 Report Share Posted January 13, 2015 W goes to power(batt.), and WL goes to dash lamp on a 1982 Datsun diesel harness. 1 Quote Link to comment
TasoZ24 Posted January 13, 2015 Author Report Share Posted January 13, 2015 Neat. Ill make a jumper tomorrow, see if I could get the 2 volts ive been chasing for a month Quote Link to comment
wayno Posted January 13, 2015 Report Share Posted January 13, 2015 As far as I can tell, the small "WL" wire goes to the auto choke as well as the IGN dash light, I don't know how this works, but that is all I have been able to figure out so far, I cannot seem to find a 1983 Nissan 720 wiring diagram. The big "W" wire in the same plug on the back of the alt. as the "WL" wire, goes to the fusible link which goes to the battery, so that would be hot/the energizer to make the alt. work. It's hard for me to do electrical in person, let alone over the internet, but I have a 1984 service manual, and that is what it says as far as I can tell. Quote Link to comment
TasoZ24 Posted January 13, 2015 Author Report Share Posted January 13, 2015 I have the diagram in the book, thanks anyhow. The voltage regulator is the problem though, gunna run the wires for the whole length of them tomorrow and look for bad things. Should 12v be present in all wires from alternator with key on? Any with key off? 1 Quote Link to comment
thisismatt Posted January 13, 2015 Report Share Posted January 13, 2015 S should have battery voltage and L should be ground or close to it, before excitation. When the alt excites, L should start outputting battery voltage which cancels out the 12v supplied to the lamp, turning the lamp off. 1 Quote Link to comment
TasoZ24 Posted January 13, 2015 Author Report Share Posted January 13, 2015 Can having these reversed mess up the regulator? Noticed this after I got the book (two days ago), the adapter that was on the harness was switched. Sure thats not good but first alt worked fine, I assume, never having problemss with light or radio 1 Quote Link to comment
thisismatt Posted January 13, 2015 Report Share Posted January 13, 2015 Yes, can fry it. 1 Quote Link to comment
TasoZ24 Posted January 13, 2015 Author Report Share Posted January 13, 2015 Stupid question... already fixed but no different, new alternator tomorrow and just maybe... 1 Quote Link to comment
TasoZ24 Posted January 13, 2015 Author Report Share Posted January 13, 2015 Thanks guys. Been playing with these wires so much, got truck cheap due to wiring issues. Finally messed up enought to where I have to do something about. Looking good though, and a lot easier than my D21 1 Quote Link to comment
wayno Posted January 13, 2015 Report Share Posted January 13, 2015 I stand by this statement I made, it's correct for an 83, just done in a confusing way in the 83 harness. W goes to power(batt.), and WL goes to dash lamp on a 1982 Datsun diesel harness. 1 Quote Link to comment
TasoZ24 Posted January 13, 2015 Author Report Share Posted January 13, 2015 Ive heard of this jump being done before to ensure voltage. My engine is the california version,btw, fuct due too smog and emissions. 1 Quote Link to comment
TasoZ24 Posted January 14, 2015 Author Report Share Posted January 14, 2015 Replaced alternator for third time still no light or charge. Took off dash and cleaning cluster again. So what I have here is two wires on one ring on outpost with battery volts at all time, the t plug with the little wire going to relay with battery at all times up top and llamp on bottom with ground unless ON.. this seem right? 1 Quote Link to comment
wayno Posted January 14, 2015 Report Share Posted January 14, 2015 OK, the big black and white wires go to the battery, the other two wires that go into the plug with the brown top are a large white wire that goes to the battery, it has power all the time, the small white/blue line wire basically goes to the ignition switch, so it only has power when the key is on, I tested this on my 85, that is how it is, if you have something wired different, it's not likely going to work. 1 Quote Link to comment
thisismatt Posted January 14, 2015 Report Share Posted January 14, 2015 Replaced alternator for third time still no light or charge. Took off dash and cleaning cluster again. So what I have here is two wires on one ring on outpost with battery volts at all time, the t plug with the little wire going to relay with battery at all times up top and llamp on bottom with ground unless ON.. this seem right? The top of the T should go to battery by some means. This is your sense wire - it senses the battery/system voltage and adjusts the output voltage accordingly. The leg of the T needs to go to your charge lamp, and the other side of the charge lamp should be hot with ignition on. You should be able to unplug the T connector and short the T leg to ground and have the charge light illuminate with the ignition on. If it's not illuminating, that's probably your issue - it's not getting power on the cluster end. 1 Quote Link to comment
TasoZ24 Posted January 14, 2015 Author Report Share Posted January 14, 2015 The spiderweb was scary when I got the truck. Cut and spliced into everywhere. Alternator was already toast when I got it along with most other components. The previous owner cared more for the interior and stereo. I have all the wiring accessible right, and the wiring diagram is not helping. Which fuse does this all tie into? Meter/flasher? 1 Quote Link to comment
TasoZ24 Posted January 14, 2015 Author Report Share Posted January 14, 2015 Im getting around 8v at blue plug from wht/blu wire (which goes to cluster). Diagram shows yel/ red into fuse after lamp. 1 Quote Link to comment
wayno Posted January 14, 2015 Report Share Posted January 14, 2015 Your getting 8v when the key is on or off? I showed a full 12 volts when I unplugged the plug from the alternator and tested the white/blue line wire when the ign. was on, I showed nothing with the key off. All large wires had 12v all the time, key on or off. Im getting around 8v at blue plug from wht/blu wire (which goes to cluster). Diagram shows yel/ red into fuse after lamp. 1 Quote Link to comment
TasoZ24 Posted January 14, 2015 Author Report Share Posted January 14, 2015 Getting 8.4 while on. Will chase this guy down again tomorrow. Where does this tie into fuse box? Im going crazy having alternator dreams, I need to figure this out. Still dont know how to post pics. 1 Quote Link to comment
wayno Posted January 14, 2015 Report Share Posted January 14, 2015 This is the best I could do on the scan. 1 Quote Link to comment
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