fufu Posted September 10, 2008 Share Posted September 10, 2008 "Common" Fuse keeps blowing upon connecting the battery terminals Hi guys, Everytime i connect the battery up to the car, the common fuse blows. Could anyone tell me what items are connected to this circuit? I've checked all my points and plugs and the harness doesn't seem to be shorting anywhere. At first i thought it was my alternator or my starter but after cleaning it up, i haven't got much of a clue now. *edit* Some information about my car: It is a 1971 Datsun 240z, the fusebox is located behind the ash tray in the centre console. Your guidance is much needed. Regards, Fu Quote Link to comment Share on other sites More sharing options...
fufu Posted September 10, 2008 Author Share Posted September 10, 2008 Just had a PM stating that its the amp meter. I'll check it out and return with my results soon. Quote Link to comment Share on other sites More sharing options...
fufu Posted September 11, 2008 Author Share Posted September 11, 2008 Utter failure today. Still popping fuses. However i think its my old rusty alternator thats the culprit. Would a short in the alternator cause the "Common" 20A fuse to blow? Does anyone know how i can test it? The auto-electrician guy said... i should try turning the car on without having the white/red cable plugged into the back of the alternator. So i'm thinking about giving that a go tomorrow. Upon closer inspection, the alternator has seen better days. A alternator point was really corroded upon further inspection, hidden away by the protector cap. On the other hand i did do the volt/fuel gauge conversion... i don't know if it works yet... its pretty much a straight swap using the existing harness. I also did the temp/pressure gauge, exact same process, using the same existing harness. Tomorrow i'll test the alternator and also install a later model clock, see if its a straight swap like the other two gauges. *EDIT* some more information about the problem i'm facing... When i unplug the... big white/red cable it still pops. However if i unplug the corresponding "common fuse" opposite cable to that of the white/red which is the black cable... it doesn't pop the fuse, upon i connect the battery. This black cable runs out towards the engine bay... as I've tried disconnecting it at where the inner dash harness meets the engine harness. Once again this... doesn't pop the fuse. Following this black cable(really thick/big) out to the engine bay leads me to many places. Quote Link to comment Share on other sites More sharing options...
gwnwar Posted September 12, 2008 Share Posted September 12, 2008 I would guess your short is out forward of the dash/eng harness and the fuse box. Don't add or change anything else till you find the short. pull the wires off the volt meter and the temp presure gages and re check. Does it do it with all wires off the alt. You do have the w/r wire to the insolated lug and the black to the ground lug on the alt right. Quote Link to comment Share on other sites More sharing options...
fufu Posted September 12, 2008 Author Share Posted September 12, 2008 I would guess your short is out forward of the dash/eng harness and the fuse box. Don't add or change anything else till you find the short. pull the wires off the volt meter and the temp presure gages and re check. Does it do it with all wires off the alt. You do have the w/r wire to the insolated lug and the black to the ground lug on the alt right. The problem i'm facing won't even let me start the car. The moment i attach the battery leads to the battery... flash of light in the cabin and i know the fuse is blown. So it hasn't gone anywhere in a while. Once that fuse has gone, nothing works. No power what so ever to any part of the car. The only thing that I've found that works once the fuse has popped is the engine bay light. I've got the isolated W/R wire hooked up to (A) on the alternator and the black wire on (E) on the alternator. Nothings been touched since i dropped it off at the panel beaters about 8 months ago. I'm gonna disconnect the whole alternator and see if the car still pops fuse upon connecting the battery terminal. It could be the alternator hasn't had a good workout and has built up rust making it short? I'll know shortly. Cheers for the heads up Gwnwar. Quote Link to comment Share on other sites More sharing options...
gwnwar Posted September 12, 2008 Share Posted September 12, 2008 Have you unpluged the volt regulator and rechecked for short. If you don't have a wire dig. try this http://www.autozone.com/az/cds/en_us/0900823d/80/1d/1d/80/0900823d801d1d80/repairInfoPages.htm or just www.autozone.com and look for wire dig or repair info pages sorry for this but..your batt is hooked up right not reversed?? Quote Link to comment Share on other sites More sharing options...
fufu Posted September 13, 2008 Author Share Posted September 13, 2008 Ok, i'm back from a good 4 hour session with mucking around with the electronics. I'm gonna take a stab and say its a ground issue now. I tried disconnecting all sub-harneses and i even took out all the fuses except the main "common" fuse and it still popped when i connected the battery up. I even disconnected all the sub harnesses and left the big red, white/red and black wire running from the engine bay into the cabin wiring harness... still pops that fuse. Fairly sure I've got the battery connected the right way. With the 2 large black cables going to the negative and a fusible link to the positive. Fusible link still works, did a beep test. I pulled out the cables to the alternator and it still pops that common fuse. Pulled out the harness from the volt regulator, still pops fuses. I'm gonna have to cut up the harness wrapping and see if theres any cables that have burnt. It's definately got something to do with the main power grid and/or grounding. But the weird thing was I've sanded down all the ground points and surfaces. Weird problem. I'm at my wits end. I mean the cars only been there for like 8 months and they didn't touch any of the wiring. So problematic this Zed. Quote Link to comment Share on other sites More sharing options...
woldson Posted September 13, 2008 Share Posted September 13, 2008 Man that sucks. Been watching you get through this problem, and thought the alternator might be it,,,,,,, no such luck! Stick with it, I really want to see what you come up with. With how fast you blow that fuse, it dose sound like a DEAD short. On a personal note, I'm thinking about inventing in the maker of 20amp fuses;) Quote Link to comment Share on other sites More sharing options...
AK-Z Posted September 13, 2008 Share Posted September 13, 2008 I would use a voltmeter on the main fuse connections and see how much amperage pull is happening. Do you have a aftermarket fuel pump? I've seen issues where it would popo the main fuse, because it wasn't grounded well. Quote Link to comment Share on other sites More sharing options...
fufu Posted September 13, 2008 Author Share Posted September 13, 2008 I would use a voltmeter on the main fuse connections and see how much amperage pull is happening. Do you have a aftermarket fuel pump? I've seen issues where it would popo the main fuse, because it wasn't grounded well. Cheers, to all of you for helping me out and giving me support through this dark hour. To AK-Z, the zed is completely stock. I've even disconnected that rear cabin harness(lights and fuel sensor - car still runs the mechanical fuel pump) and tested it and it still pops the fuse. The only thing i haven't tried is... disconnecting all the gauges. I'm fairly sure my new 260z volt/fuel is good and my new 260z temp/pressure gauge is good as well as I've only just installed it after the problem started - assumed it would fix the problem. The only 2 gauges i have not touched are the rev and the clock.. which also uses ground. I will also disconnect all the bulbs. My last hope is the starter as I've read in other posts its like another battery terminal and if that shorted that would lead to the same outcome? I've done heaps of searches and a lot of reading through past posts but nothing remotely even comes close to this problem. Quote Link to comment Share on other sites More sharing options...
naviathan Posted September 13, 2008 Share Posted September 13, 2008 You know, this sounds just like a reversed battery. Remember the positive side is next to the fender and the negative toward the engine. Quote Link to comment Share on other sites More sharing options...
fufu Posted September 14, 2008 Author Share Posted September 14, 2008 You know, this sounds just like a reversed battery. Remember the positive side is next to the fender and the negative toward the engine. I've got a RHD 240z. The battery has the fusible link on the positive terminal and the negative terminal has, 2 cables, the negative cable going to the starter and the ground cable hooked up to the firewall. Is this correct? Quote Link to comment Share on other sites More sharing options...
woldson Posted September 14, 2008 Share Posted September 14, 2008 Crud....inventing.....let me rephrase that.... investing:) Quote Link to comment Share on other sites More sharing options...
gwnwar Posted September 15, 2008 Share Posted September 15, 2008 You said the neg cable to the starter?? ONLY if it's attched to the mounting bolt to hold the starter to the tranny... NOT to the solenoid B termeral on the solenoid.. Your positive cable from the batt should go to starter solenoid B lug.. and a black wire also from the same lug to a fuse link.. If your batt is not marked the larger of the two posts is the positive. From the neg post on batt. there should be a heavy cable to the engine and a light gage to the firewall.. Make sure the wires to the solenoid B lug don't turn/spin when tightning and ground out to the starter housing.. Quote Link to comment Share on other sites More sharing options...
fufu Posted September 15, 2008 Author Share Posted September 15, 2008 You said the neg cable to the starter?? ONLY if it's attched to the mounting bolt to hold the starter to the tranny... NOT to the solenoid B termeral on the solenoid.. Your positive cablefrom the batt should go to starter solenoid B lug.. and a black wire also from the same lug to a fuse link.. If your batt is not marked the larger of the two posts is the positive. From the neg post on batt. there should be a heavy cable to the engine and a light gage to the firewall.. Make sure the wires to the solenoid B lug don't turn/spin when tightning and ground out to the starter housing.. Hi gwnwar, i have sanded both points and made sure the bolts on both were as tight as i can turn them. They look very similar to the picture in this thread. http://forums.hybridz.org/showthread.php?t=130411&highlight=solenoid+picture However I've got my positive cable with the L shaped bracket and its pointing away from the starter. Is it possible for the starter to get rusted internally and short from the inside? This must be a silly question but... I've yet to test the polarity of the battery. There are clear signs depicting negative and positive, however is it possible for a manufacturer to put the wrong signs on a battery? I'll use a multimeter tonight. Quote Link to comment Share on other sites More sharing options...
gwnwar Posted September 16, 2008 Share Posted September 16, 2008 If your wires on the starter look like the photo they are on right..and if your heavy wire from the starter is going to the fattest batt post it is right. You do still have the wires to the alt off right leave them off till you find the problem..Have you unpluged your ignition switch connector and checked. After that check pull the connectors from the combo switch lights/wipers one at a time. This long distance trouble shooting with time zones sucks. What color wires go to your common fuse and what color to the fuse attached to it. is it black or black with white tracer. You might also pull the green wire from the fuel pump.. I can't find a good wire sheet of the fuse box. Quote Link to comment Share on other sites More sharing options...
fufu Posted September 16, 2008 Author Share Posted September 16, 2008 If your wires on the starter look like the photo they are on right..and if your heavy wire from the starter is going to the fattest batt post it is right. You do still have the wires to the alt off right leave them off till you find the problem..Have you unpluged your ignition switch connector and checked. After that check pull the connectors from the combo switchlights/wipers one at a time. This long distance trouble shooting with time zones sucks. What color wires go to your common fuse and what color to the fuse attached to it. is it black or black with white tracer. You might also pull the green wire from the fuel pump.. I can't find a good wire sheet of the fuse box. The wires going to that fuse is the big white/red and a blue cable - however the blue cable(about 5cm) has a disconnect point(plug/socket) and then turns into a black cable. This black cable then runs all the way to the engine bay i believe. Quote Link to comment Share on other sites More sharing options...
gwnwar Posted September 17, 2008 Share Posted September 17, 2008 What was the car in the shop for ..body work?? Have you tryed the things I wrote about..pulling wires off the amp gage, pull plug from ign.witch, pull plugs from combo switch, all fuses still out of fuse box but the common, wires off the alt, volt reg., and starter and the two wires to the starter B lug bolted together so power goes to fuse link., pull wire from fuel pump. Leave all above unpluged till answer found.. did you say that you unpluged the plugs going into the eng compartment and it does not blow fuses. It's midnight here guess it's around noon there. going to bed got to get up in 6 hrs. good luck Quote Link to comment Share on other sites More sharing options...
Jer260Z Posted September 29, 2008 Share Posted September 29, 2008 I started my 260z this afternoon, idle for about 10 minutes.. It was raining so I hit my lights then my wipers. Soon as I turned on my wipers one of my fusible links blew. I tried to replace it with another but sparked so I held off. Disconnected the wiper motor - same thing.. Anyone have any ideas? Quote Link to comment Share on other sites More sharing options...
Careless Posted September 29, 2008 Share Posted September 29, 2008 I started my 260z this afternoon, idle for about 10 minutes.. It was raining so I hit my lights then my wipers. Soon as I turned on my wipers one of my fusible links blew. I tried to replace it with another but sparked so I held off. Disconnected the wiper motor - same thing.. Anyone have any ideas? your whiper motor moved and possibly shorted two wires or your whiper switch is sticking. have you tried unplugging the switch? Quote Link to comment Share on other sites More sharing options...
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