74Adam Posted March 1, 2015 Share Posted March 1, 2015 This is a 78 model with a stick. No floor temp sensor. Anyway, the "PARK/TAIL" fuse is blowing. This is the 15 amp fuse in the top right corner of the fusebox. I've narrowed it down the C-6 connector. There are three connectors at the white junction block under the passenger side footwell that connect to the dash harness: C-5, C-1 & C-6 which are colors white, blue and black, respectively. If I unplug C-6 ONLY the fuse doesn't blow. My question is what does C-6 account for? In the FSM, it is impossible to tell (at least for me) from the layout drawings where those wires go versus the other two connectors. I'm trying to get better at reading wiring schematics but it's a weak point for me so if anyone could shed some light I would appreciate it. thanks Quote Link to comment Share on other sites More sharing options...
Miles Posted March 1, 2015 Share Posted March 1, 2015 (edited) See if you can Google a pdf copy of the 78 280Z schematic. The pdf is easier to read and you can enlarge it to better see the details. See AtlanticZ for some electrical schematics: http://atlanticz.ca/zclub/techtips/electrical.htm Edited March 1, 2015 by Miles Quote Link to comment Share on other sites More sharing options...
NewZed Posted March 1, 2015 Share Posted March 1, 2015 Pull all of your tail lights and see if the fuse still blows, or check for short to ground with a meter (save some fuses). Look inside the sockets to make sure they're not touching. I had a contact in a socket get hot enough to melt its way sideways to a short. The bulb contacts get old and oxidized, and the oxidation heats up. Quote Link to comment Share on other sites More sharing options...
74Adam Posted March 1, 2015 Author Share Posted March 1, 2015 I'm sorry, I should have provided more detail. I've removed every exterior light and the taillights. Cleaned the sockets and bulb contacts with red scotchbrite pad and contact cleaner and reinstalled with di-electric grease. The turn signal and hazards will work (front and rear lights) and the headlights and dome light work. Dash lights are out, as are all parking lights as well as brake lights. Quote Link to comment Share on other sites More sharing options...
NewZed Posted March 1, 2015 Share Posted March 1, 2015 reinstalled with di-electric grease. But what happens if you leave them removed? I like to work from the simplest case, then make it more complicated until the answer shows. If there's no short with all of the lights removed, then you don't have to worry about all of the stuff between the power and the sockets. If the short still happens with the lights removed, you can still leave all of them out until you make the short go away. Start as simple as possible. You might even have a defective bulb with an internal short, or a short across its electrodes. It's possible. Quote Link to comment Share on other sites More sharing options...
74Adam Posted March 1, 2015 Author Share Posted March 1, 2015 Oh jeez, I see what you're saying. Yeah, that makes sense. Oh, and this is probably assumed but the fuse doesn't blow until I rotate the combo switch to the parking light setting. Well, the deal is that my car isn't where I live so I only get to work on it on Saturdays so I'll try some of this stuff and report back. Miles, thanks for the links to the pdf's. I'll check them out but I don't think "clarity" is an issue, I just need to teach myself how to read a schematic better. Funny, I'm a civil engineer so you would think stuff like this would be right up my alley but when it comes to electricity, I struggle :-/ Quote Link to comment Share on other sites More sharing options...
Miles Posted March 1, 2015 Share Posted March 1, 2015 Did you remove the marker lights? There are two wires connecting the marker lights. Did you reconnect the wires correctly? For example, on a 240Z rear marker light one wire is hot and the other wire is a ground. When I had my 240Z painted, the shop hooked up the right rear marker light backwards so each time I turned on the lights the fuse for the parking/marker/dash lights would blow. When things like this happen ask yourself what did I do to the car just before the fuse started blowing. Like retracing your steps to find lost keys. Quote Link to comment Share on other sites More sharing options...
74Adam Posted March 2, 2015 Author Share Posted March 2, 2015 Yeah, I removed front and rear marker lights, front turn signals and all the lights in the tail housing (back up, brake, turn). I'll make sure everything is plugged in correctly but those plugs are all stock and they only connect one way. The brake light with the double lead has offset pins on the bayonet bulb that can only slide in the socket one way. Nevertheless, I will double check them all. Quote Link to comment Share on other sites More sharing options...
Miles Posted March 2, 2015 Share Posted March 2, 2015 Oh jeez, I see what you're saying. Yeah, that makes sense. Oh, and this is probably assumed but the fuse doesn't blow until I rotate the combo switch to the parking light setting. Well, the deal is that my car isn't where I live so I only get to work on it on Saturdays so I'll try some of this stuff and report back. Miles, thanks for the links to the pdf's. I'll check them out but I don't think "clarity" is an issue, I just need to teach myself how to read a schematic better. Funny, I'm a civil engineer so you would think stuff like this would be right up my alley but when it comes to electricity, I struggle :-/ Trouble shooting automotive electrical problems is a different skill mix compared to engineering. As a retired mechanical engineer I enjoy the hands-on problem solving. Quote Link to comment Share on other sites More sharing options...
Miles Posted March 2, 2015 Share Posted March 2, 2015 (edited) Yeah, I removed front and rear marker lights, front turn signals and all the lights in the tail housing (back up, brake, turn). I'll make sure everything is plugged in correctly but those plugs are all stock and they only connect one way. The brake light with the double lead has offset pins on the bayonet bulb that can only slide in the socket one way. Nevertheless, I will double check them all. My marker lights just had two pig tails with bullet connectors. One of them got flipped. As NewZed stated above, unplug all of the lights and reconnect until the fuse blows. My thought is you have a hot wire that got connected wrong when you reinstalled the lights. Edited March 2, 2015 by Miles Quote Link to comment Share on other sites More sharing options...
74Adam Posted March 2, 2015 Author Share Posted March 2, 2015 No no no, the reason I cleaned all the bulb connections was BECAUSE I thought one of them might be the cause for the blown fuse. In other words, I was hoping I would get lucky that it would be something easy...lol. Sorry if I didn't make that clear. Quote Link to comment Share on other sites More sharing options...
Miles Posted March 2, 2015 Share Posted March 2, 2015 So you didn't unplug and lights when cleaning the sockets? Quote Link to comment Share on other sites More sharing options...
NewZed Posted March 2, 2015 Share Posted March 2, 2015 Here's a link to one with some color. Not perfect but easier to read. Looks like C6 feeds the gauges, which makes sense since my gauge lights died when the tail lights did. That was the clue. You might try unplugging sub-harnesses also. Unplug C6 and see if the tail lights work. Or take out all of the lights and see if C6 still blows the fuse. http://www.classiczcars.com/topic/42132-a-somewhat-color-wiring-diagram-for-1978-280zsenjoy/ Quote Link to comment Share on other sites More sharing options...
74Adam Posted March 2, 2015 Author Share Posted March 2, 2015 Miles, no I didn't unplug the light pigtails from the body harness plugs when I cleaned the sockets. Is that what you are asking? NewZed, thanks for the link. I downloaded the PDF and glanced at it. Will certainly spend more time pouring over it when I get a chance. I believe you are right about C-6. I looked through the FSM at all the individual wiring schematics. I wanted to find the ones that show BOTH the green/blue wire (labeled "GL") coming out of the PARK/TAIL fuse AND that the system routes through C-6 in some way. I found three: "Meter illumination system" on page BE-15, "glove box, cigarette lighter & ashtray illumination" page BE-17 and "Heater illumination" on page BE-54. So, that accounts for all the lighting in the dash, doesn't it? One thing it ISN'T is the rheostat. Before I did anything else, I unplugged the rheostat individually and the fuse still blew. Sucked, because the thing was a bitch to unplug...lol. Quote Link to comment Share on other sites More sharing options...
TimZ Posted March 2, 2015 Share Posted March 2, 2015 (edited) This is a 78 model with a stick. No floor temp sensor. Anyway, the "PARK/TAIL" fuse is blowing. This is the 15 amp fuse in the top right corner of the fusebox. I've narrowed it down the C-6 connector. There are three connectors at the white junction block under the passenger side footwell that connect to the dash harness: C-5, C-1 & C-6 which are colors white, blue and black, respectively. If I unplug C-6 ONLY the fuse doesn't blow. My question is what does C-6 account for? In the FSM, it is impossible to tell (at least for me) from the layout drawings where those wires go versus the other two connectors. I'm trying to get better at reading wiring schematics but it's a weak point for me so if anyone could shed some light I would appreciate it. thanks From looking through the schematics, here are the wires that could cause the Park/Tail fuse to blow (barring anything weird like a screw shot through the harness): Green/White wire in C6 gets power from the Park/Tail Fuse, fed through the headlamp switch when in either the Parking Light or Headlamp positions. It feeds all of the dash illumination lamps (gauge lamps, cigarette lighter lamp, and glove box lamp), any of which could short and blow the fuse. Side Marker and Clearance lamps (also Green/White from the HL Switch) get power from Park/Tail fuse, but do not go through C6. Center console illumination lamps (also Green/White from the HL Switch) also get fed from the Park/Tail fuse, but do not go through C6. Edited March 2, 2015 by TimZ Quote Link to comment Share on other sites More sharing options...
TimZ Posted March 3, 2015 Share Posted March 3, 2015 (edited) From looking through the schematics, here are the wires that could cause the Park/Tail fuse to blow (barring anything weird like a screw shot through the harness): Green/White wire in C6 gets power from the Park/Tail Fuse, fed through the headlamp switch when in either the Parking Light or Headlamp positions. It feeds all of the dash illumination lamps (gauge lamps, cigarette lighter lamp, and glove box lamp), any of which could short and blow the fuse. Side Marker and Clearance lamps (also Green/White from the HL Switch) get power from Park/Tail fuse, but do not go through C6. Center console illumination lamps (also Green/White from the HL Switch) also get fed from the Park/Tail fuse, but do not go through C6. BTW - this indicates that the fuse shouldn't blow until you turn on the parking/headlights using the headlamp switch, a detail that you didn't mention having observed. Is that what you are observing? Edit: I just saw where you did indeed mention this. Check the gauge illumination bulb sockets, cigarette lighter illumination bulb socket and the glove box lamp socket for shorts to ground. Edited March 3, 2015 by TimZ Quote Link to comment Share on other sites More sharing options...
74Adam Posted March 3, 2015 Author Share Posted March 3, 2015 Thanks Tim. Yeah, it occurred to me at some point that I might want to mention that small detail...lol. I'm starting to wonder if this is the car gods way of telling me that it might not be a bad idea to remove my dash and go through everything :-/ Quote Link to comment Share on other sites More sharing options...
NewZed Posted March 3, 2015 Share Posted March 3, 2015 There are several areas where wires get stretched and moved and can chafe. The console harness, and the heater control panel, for example. Both easier to remove than the dash. Almost better to get a short and have to fix it than have one of those lights that goes on and off randomly. Crap, I have to fix it, wait, it's working now. Quote Link to comment Share on other sites More sharing options...
74Adam Posted March 3, 2015 Author Share Posted March 3, 2015 Ha ha, I know what you mean. Hopefully I will find something definitive. Quote Link to comment Share on other sites More sharing options...
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