Electrical Issue - Blowing fuse when connecting battery

[Stresspuppy]

Well, I am THIS close to getting the restoration of my 72 done. But there always has to be that one snag that slows things down. Give me a wrench and ask me to do just about anything, I'm good to go. Ask me to diagnose an electrical problem/short, ha.

 

Quick back story... Had everything out of my car and when inspecting the dash wire harness, it was in pretty rough shape. The ignition wire had shorted on the PO and the repair was pretty bad. Instead of messing with it, I found a very good wire harness from a 72 on ebay. I inspected then I got it and everything looked great. I put in in the dash and the dash back in the car. The engine bay harness had some issues as well, so I pulled it apart up to the alternator and replace some wires, but one at a time to ensure I didn't mess something up. 

 

Now to the fun. I hook everything up and the instant I put the positive cable on the battery, the fusible link melts. Not a happy camper. So I created my own version of the link with an inline fuse (30A) just to be able to make sure there aren't any issues and things like lights, etc. work. I'll replace the link before trying to start it. When the fuse blows, it is always at the starter. The fuses in the car are fine. 

 

Wiring - Starter:  White wire from engine bay harness goes to fusible link then to the same bolt on the solenoid/starter that the positive battery cable is connected to. Black with yellow wire goes to the blade plug on the solenoid. Negative battery cable goes to bolt in trans bell housing. 

 

Wiring - Alternator: White/Red wire to the insulated lug on alternator. Black wire to appropriate terminal. Plug where it goes.

 

Wiring - Dash: All appropriate connectors between 3 harness connected (noting White to White, White/Red to White/Red, Black to Black). White and White/Red wires go to the appropriate sides of the amp meter. White/red goes to screw on back of fuse block.

 

In my diagnosis, I unhooked the ignition switch and the combo switches. Same problem. I completely disconnected the alternator, same problem. I think I have been through 8 or so fuses so far, and I'm getting frustrated. I'm not sure where to look next. If someone could help point me in the right direction, or give me an idea of how to narrow things down, i'd appreciate it. I have a wiring diagram and a meter, but I'm not always sure what I am looking at/for. 

 

(I have 2 car shows in 8 days and need to get this done. I will owe you more than you know if you can help me stop banging my head against the garage floor. And my wife will thank you if it gets me to stop being so grumpy. Thanks in advance.)

[z240]

We can't tell you what the problem is, but here's how to go about finding it

 

You-all got a short to the chassis somewhere on the power side of the circuit.  The fact that it blows the the fusible link before any fuse says it not something any fuse powers. So its big stuff.

 

First disconnect the alternator white wire and see if that stops the fuse blow.

Then pull the fuse block its mounting and make sure the white red wire there is not touching anything it shouldn't (metal or chassis).

 

Get your multi-meter out. No multi-meter? Get one. 8-10 bucks at harbor freight or auto-parts store. It tells you if point A is electrically connected to point B and what the voltage is at any point in the harness. This is a requirement for finding electrical problems, short of (pun there, sorry.,,,) finding an obvious place where the white wire's insulation is broken/cracked/worn and touching the metal part of the car.

 

That fat white wire with the fusible link that blew, right off the starter that goes into the harness goes a couple of easy places to check.

 

1. To the ammeter

2. The fuse block under the front of the console.

3. To the ignition switch.

 

Trace that wire back and find out where it rubbed through and shorting to the metal of the car.

 

The multimeter will tell if you have a connection between the metal of the car and that white wire now. You should not, but you likely do. Keep disconnecting things until the white wire is no longer connected to the metal, then look between the last place you disconnect and where you just disconnected.

 

Good luck.

[seattlejester]

Here's the wiring diagram I like to use. 

 

http://www.atlanticz.ca/zclub/techtips/wiringdiagrams/240z/1972_240z.gif

 

My similar problem came from shorting the white/red wire going to the fuse box directly onto the chassis, it sounds like you have that one connected correctly, bolted onto the back of the fuse box.

 

Another common short is a dirty or loose connection to the starter/bell housing area. Make sure the ground cable and the main power cable are firmly attached, with the ground cable cleanly connected on top of the starter (bolt head, then locking washer, then circle terminal, then starter, the transmission cover, then bell housing). Taking this terminal off and checking would test whether it is a fault with the starter.

 

z240 is right on the multimeter front, having one is a great boon, not having it will only leave guessing and checking and more frustration. Picking up a set of alligator clips will also be really helpful in finding the short. Pictures of the main problem areas (battery, alternator, starter, fuse) may be helpful if possible.

 

Basically you are putting too many amps down the wrong path, the power has found a much easier ground than going through all of the wiring harness and has decided to ground through that path, causing the fuse to melt from the large amperage trying to travel the path. Is the fuse popping with the body harness unplugged? It sounds like it is limited to the engine bay. If you have tried with the alternator unplugged and the key in the off position it is limited to a short in the body under the dash (ammeter, fuse box, fire wall) or the starter. If the wiring harness is unmodified or undamaged going into the body then it more so points towards ammeter, fuse box (both white and white red), or it is reserved in the engine bay, pointing towards the starter or a misgrounded wire.

 

Well lit, high quality pictures with labels will help visually, voltage readings of the wires will help as well.

[Domzs]

Stop wasting money on fuses . Use a circuit breaker or a light bulb . Light bulb method would be the easiest way to narrow down your short .

[Stresspuppy]

Thanks for the quick replies. 

 

First disconnect the alternator white wire and see if that stops the fuse blow.

Then pull the fuse block its mounting and make sure the white red wire there is not touching anything it shouldn't (metal or chassis).

 

Alternator wasn't connected, ignition switch was disconnected and fuse block is not mounted.

 

 

Get your multi-meter out. No multi-meter? Get one. 8-10 bucks at harbor freight or auto-parts store. It tells you if point A is electrically connected to point B and what the voltage is at any point in the harness. This is a requirement for finding electrical problems, short of (pun there, sorry.,,,) finding an obvious place where the white wire's insulation is broken/cracked/worn and touching the metal part of the car.

 

I have a meter, but since the fuse blows, I am assuming I am getting no voltage so I just disconnect the battery. I do use continuity to trace the wires, but not sure if that is giving me false info.

 

 

Trace that wire back and find out where it rubbed through and shorting to the metal of the car.

 

Both the white and white/red wires in the engine bay harness were replaced because of age/brittleness/short from PO that melted the covering on a few wires. I replaced one wire at a time to ensure things weren't crossed, etc. The harness was then re-wrapped and nothing is in contact with the body.

 

If continuity is something I can use to help track things, I noticed that with the harnesses disconnected, if I try the white and white/red under the hood, no continuity. if I do the same for those two wires under the dash, I do have continuity. Is that the way it should be? If I use the white wire from the dash and the body as a ground, should I have continuity? How about White/Red to the body? 

 

 

 

Here's the wiring diagram I like to use. 

 

http://www.atlanticz.ca/zclub/techtips/wiringdiagrams/240z/1972_240z.gif

 

Thanks. This is a bit more simple. I'll review.

 

 

Basically you are putting too many amps down the wrong path, the power has found a much easier ground than going through all of the wiring harness and has decided to ground through that path, causing the fuse to melt from the large amperage trying to travel the path. Is the fuse popping with the body harness unplugged? It sounds like it is limited to the engine bay. If you have tried with the alternator unplugged and the key in the off position it is limited to a short in the body under the dash (ammeter, fuse box, fire wall) or the starter. If the wiring harness is unmodified or undamaged going into the body then it more so points towards ammeter, fuse box (both white and white red), or it is reserved in the engine bay, pointing towards the starter or a misgrounded wire.

 

Well lit, high quality pictures with labels will help visually, voltage readings of the wires will help as well.

 

Dumb question, but if the fusible link blows right away, the overall circuit is broken so a voltmeter isn't going to do much is it? This is why I have been trying to do things with continuity, but may be on the wrong track there.

 

I will try a few of the combinations you mention. Fuses are cheap, right? But the arcing at the battery is taking a toll on the positive terminal. 

[Stresspuppy]

Stop wasting money on fuses . Use a circuit breaker or a light bulb . Light bulb method would be the easiest way to narrow down your short .

 

How would I do this? I would definitely like to stop blowing fuses and having the arc from the cable to the battery terminal when I connect it.

[Domzs]

How would I do this? I would definitely like to stop blowing fuses and having the arc from the cable to the battery terminal when I connect it.

Find a way to connect a light bulb to your fuse holder ( the blown one ) . I use an old light socket with 2 wires at the end . If you have a dead short then the bulb will light up like a Xmas tree . Start moving wiring harnesses or disconnect components until the light goes out . You will find a short when the light goes out .

Edited October 4, 2013 by Domzs

[seattlejester]

Basically there is one wire/path that is instantly connecting the battery to a ground. Having the fuse disconnected and checking the voltage from one end to a ground using your multimeter will tell you which wires are energized. Continuity check is a good way to check without having the battery wired up. I would start on the other side of the fuse that keeps popping and test continuity and see if something is grounding without going through an accessory/power drawing unit. With such an old car I can only think of a few items that it could be. 

 

Illustration of the light bulb trick:

 

http://www.crookedriverwriter.com/index.php?/Automotive-Topics/the-old-headlight-trick.html

 

basically the filament acts as a fuse, if you ever look at a fuse and see how it heats up before it pops, it basically does the same thing, except a light bulb is designed to stay hot. Wire it in line, with the popping fuse and note when the light turns off. Whatever you just unplugged is your short.

Edited October 4, 2013 by seattlejester

[Stresspuppy]

I disconnected the harnesses and hooked up the battery. No short. So definitely under the dash. I hooked a lead of the meter to the white wire under the dash where it connects to the engine harness and touched the body. Continuity. I took the ammeter off, but left wires connected, to make sure the wires were connected properly (white to +, white/red to - which is right according to diagrams). I went to check again and no continuity. But if I touch the body of the ammeter, i get continuity. So would that mean it is the ammeter or do I now start chasing through the white/red wire?

 

I replaced the dash harness on my car and carefully inspected it before I put it in. No cuts or abrasions in the wrap anywhere. No frayed wires, etc. 

 

I really appreciate the input and quick responses. I am really hoping to be able to start it tomorrow but obviously have to get this sorted out first. 

[seattlejester]

So to get this straight, you unplugged the body wiring harness and no short? That's somewhat good news.

 

It means the short is limited to the main power wires which you are doing a good job of tracking down.

 

You unplugged the body harness, then checked the continuity of the white wire that feeds the + side of the ammeter to where it plugs in to the engine bay harness, proving continuity in that power wire. Good so we are now at the ammeter.

 

From this point, I am not sure what exactly you did, I am having a hard time imagining precisely, your language is clear but my head is a bit foggy. This is where pictures would help greatly. Let me try to explain some of my confusion below.

 

When you bridge the two wires that go to the ammeter, by connecting the two circle terminals together (removing the ammeter from the equation) you do not get continuity when you test? Or by removal do you mean when you pull the ammeter out of the dash? If you mean the later, continuity to the body means the ammeter is grounding through the ammeter body, which means it is some kind of strange internal short and it is grounding where the ammeter mounts. Either replace the ammeter, or bridge the wires that go to the terminals with a bolt and remove the ammeter and use a voltmeter (which is better) somewhere down range. For the purpose of the show you can keep the ammeter in, and have the two terminals that go to it attached to each other via bolt as described and completely isolated (heat shrink, electrical tape, something to keep it from shorting) if you want to maintain stock instrumentation.

 

Just for future reference, careful inspection of the externals of a wiring harness can still be insufficient at times, I once had a wire that was pinched and was cut under the electrical tape (old wires are brittle) externally harness looked fine, internally it was shorting on a separate wire. The first step to trouble shooting is to look at what was replaced exactly/never rule out anything, but you did a good job chasing the short. Hope this helps if not, come back and we can keep chasing it down. I think you do have the skill set now to keep going on your own though. Let us know how it turns out.

[ktm]

Continuity. I took the ammeter off, but left wires connected, to make sure the wires were connected properly (white to +, white/red to - which is right according to diagrams). 

 

There is your short.  The white and white/red wires at the ammeter are connected together through the ammeter.  Connecting the white/red to ground is a short.  The ammeter acts as a bridge for the white and white/red wires and shows the charging state of the battery.   Connect the white and white/red wires together and you should be good to go.

[Stresspuppy]

When you bridge the two wires that go to the ammeter, by connecting the two circle terminals together (removing the ammeter from the equation) you do not get continuity when you test? Or by removal do you mean when you pull the ammeter out of the dash? If you mean the later, continuity to the body means the ammeter is grounding through the ammeter body, which means it is some kind of strange internal short and it is grounding where the ammeter mounts. Either replace the ammeter, or bridge the wires that go to the terminals with a bolt and remove the ammeter and use a voltmeter (which is better) somewhere down range. For the purpose of the show you can keep the ammeter in, and have the two terminals that go to it attached to each other via bolt as described and completely isolated (heat shrink, electrical tape, something to keep it from shorting) if you want to maintain stock instrumentation.

 

SUCCESS!!

 

I took the ammeter out of the mix and no more shorts! Battery hooks up without a spark and the fuse doesn't blow. Once I felt good about that, I started putting back the upgrades (fuse block, starter, 280zx alternator, etc) and checked after each one. No issues! I think my hang up was not stepping back and thinking about what the ammeter does in that circuit and that it is ok to join those two wires. For some reason, my brain was saying they shouldn't be, but it's just a meter and the power has to pass through it for it to give a reading. DUH.

 

You mentioned replacing with a volt meter instead. I know they replaced the ammeter with the volt meter at some point and it would fit in. Is there any wiring change needed to do that, or is it a pretty straightfoward replacement? I need to search on this a bit but if you can give a quick answer, I'd appreciate it.

 

 

My next step is to check the various items (lights, horn, various lights, etc.) before I start it. I'm assuming I can just turn to the On position and everything should work assuming the battery is ok. Is there anything specific I should do or look for while doing this?

 

Thanks for a little "hand holding" and helping me get more comfortable with this. I think I understood it, but was scared of it (still am a little I think).

[Stresspuppy]

Question (semi-related):  I have some accessory wires for things like the headlight upgrade, etc. that have their own inline fuse. I want to hook them to the starter where the positive battery cable goes instead of to the battery terminal connector to hide the wires a bit. Any issues with doing it that way?

 

Off to the garage to test...

[Domzs]

Depends on location of your inline fuse . You want to have a fuse to protect a circuit as close to battery as you can . If the fuse is too far away and you have a short between the power source and the fuse then you will have electrical meltdown or fire . You get the picture . You can hook up all your wires to a heavy gauge wire then run it ( with an inline fuse or fusible link ) to the starter . I would rec to use a fuse block .

[seattlejester]

Congrats!

 

And I have to say kudos for being a a real go getter about tracing the wiring harness instead of throwing in the towel, I know I have been down the towel throwing road before.

 

I believe the later model cars 280z's (maybe 260z?) came with volt meters which should go in the same spot and have very similar wiring, an easy way to check would be to look up a wiring diagram available also at atlanticz.ca and see if the same terminals get power/signal from the same locations although it will look a little out of place (different height and different font) if that bothers you.

 

I bought a little voltmeter used for aquariums and added another ring terminal to the bridged wires that went to the ammeter to take a strong power reading from the battery. It feeds my little cabin display with time, cabin temperature, and voltage (clock replaced with LC-1 AFR gauge, ammeter replaced with fuel gauge).

[Stresspuppy]

Depends on location of your inline fuse . You want to have a fuse to protect a circuit as close to battery as you can . If the fuse is too far away and you have a short between the power source and the fuse then you will have electrical meltdown or fire . You get the picture . You can hook up all your wires to a heavy gauge wire then run it ( with an inline fuse or fusible link ) to the starter . I would rec to use a fuse block .

 

My longer term plan is to do a fuse block in the engine bay to clean things up a bit, but for now I have the extra power wires coming from the solenoid lug that has the cable from the positive side of the battery. Each one has an inline fuse within about 6-12 inches of it's connection to the solenoid. This should work about the same as a fuse block, but not very pretty. I have tucked things in some look to clean it up for now, but will be redoing some of the wiring after the shows.

 

 

Congrats!

 

And I have to say kudos for being a a real go getter about tracing the wiring harness instead of throwing in the towel, I know I have been down the towel throwing road before.

 

Thanks. I think I just needed some pointers and a little reassurance, which was provided here (again, thanks!). Throwing in the towel wasn't an option. Not only do I have 2 car shows coming up, but I really don't want to tell folks I was beat by simple car wiring!

 

 

I bought a little voltmeter used for aquariums and added another ring terminal to the bridged wires that went to the ammeter to take a strong power reading from the battery. It feeds my little cabin display with time, cabin temperature, and voltage (clock replaced with LC-1 AFR gauge, ammeter replaced with fuel gauge).

 

I'd like to see that setup if you have pics. For now my plan is stock gauges, but I have thought about doing something different. Always looking for different ideas for future changes/upgrades!

 

 

I started testing things tonight and not everything works. Horn works, hazards work in the rear but not the front, only some of the dash lights seem to be working. Standard "fun". So now I can use the volt meter and see what is getting power and what isn't. Hopefully it's just a couple of small things so I can move on to getting it started (didn't want to try without knowing everything is hooked up correctly).

[seattlejester]

Pre-AFR

 

I would check the sockets on the front turn signals, use the multimeter to check for either continuity from the harness to where the bulb plugs in or with the battery connected check for voltage when supplying the correct turn signal. The connection have been shown to come detached from the socket which will need re-soldering (it will be under the plastic if memory serves). Taking a look at the signaling stalk and the flashing solenoid is a good idea while you are at it. If memory serves the front one is difficultly located on the steering column box while the rear one or maybe the hazard blinker is easily accessible from the passenger side. 

 

Regarding the dash lights, the solution is surprisingly ancient, but if you tap around the gauges lights/turn them on off, you may find some of the dash lights back on. A lot of dust accumulates back there, and can cause a faulty ground. It is a 1 wire setup for the dash light bulbs, basically power goes to the bulb and the bulb grounds through the body of the gauge it is on which grounds through the metal chassis of the dash. Be very careful if you try to remove the bulbs for replacement, turn and supply the correct pressure or you may find yourself detaching the entire bulb socket which is plastic riveted or glued or something of that nature to the body of the gauge, facilitating a lengthy dash removal and reattachment of the sockets.

 

For replacements (shameless plug for a local supplier ahead) don't be tempted with LED replacements as you need the incandescent light to light up the light rings inside the gauges, if looking for replacements you want to find something that takes a similar voltage but supplies more wattage, Oliver from Z specialties was absolutely beaming about the lights he found. Made me excited, but as I only have the speedo and the oil/water gauge left it did not apply to me as much.

http://www.datsunstore.com/dash-light-bulb-7078-watts-p-1703.html

 

Now that you have experience tracking the electrical gremlins I hope everything will be working in short order . Good luck.

Edited October 6, 2013 by seattlejester

[Stresspuppy]

Thanks for the input. The dash has been out, everything cleaned very well and put back in. Yes, VERY dusty and nasty back there originally. So I can rule that one out I think. As for dash lights, when I had the dash out, I replaced them all with exactly what you referred to above so that should be good.

 

I have a very odd combination of things that work and don't, so I guess I just have to start tracking the gremlins. It's going to be a long week...

 

Is there a particular circuit or accessory that is the best to start with, or does it really matter? Also, I replaced the alternator with the 280zx and have the MSA adapter for removing the Voltage Regulator. Since I am not starting the system, I'm assuming this isn't coming into play when looking for issues with the lights, etc., but please confirm. (And I took the MSA headlight and parking light upgrades out for now so I can get things working THEN add them in. Not as dumb as I look  )

 

Thanks. Getting close...

[seattlejester]

I don't think the alternator upgrade and the voltage regulator delete would cause problems since they are plug and play and are direct replacements.

 

Easiest thing would be to pop out one of the gauges that are not lighting up and seeing if the bulb is getting any power by putting one lead on the wire and the other lead of the multimeter to a chassis ground. If it doesn't supply voltage you will have to trace where it gets power from and see why that isn't working. To my recollection the dash lights go through the rheostat and are triggered by the headlight switch. A lot of power goes through that stalk, and may have burned out the contact for triggering the dash lights, but if you say only some of them aren't working I would think it is more likely that individual bulbs either have bad grounds or are not getting power from the harness. 

 

If you painted the interior or the dash chassis, the gauges might be having a hard time grounding the the paint or the rust. Other than that I'm pretty plum tuckered out on suggestions.

 

You might have to plug in the headlights and brake lights to complete a circuit, but I really don't think you will have to. It should be safe if they are connected since the kit should be fused.

[Stresspuppy]

WOW, what an adventure. I broke down and had someone come over and help and I'm glad they did. There were things I wouldn't have figured out. Here is what I started with:

 

Rear lights would all come on for brakes, etc.

Right turn signal works in rear only

Hazards all except left front work

No headlights

No running lights

 

In the end, the solutions:

• Rear lights - short in tail light harness. Temp fix but found a good pair on eBay and purchased.
• Turn signal - Had to take switch apart and clean contacts and bend one back to proper position; Had to resolder the green/black wire to the circuit board.
• Headlights - Initially just turning on and off many times got things to start working, but left front didn't work on low but high worked for both; loose connection at plug fixed left low not working. Ended up taking switch apart to clean contacts.
• Parking lights - resolved with switch cleaning.
• Windshield washer - was working but took switch apart and cleaned anyway (did the others, why not?)
• Hazards - used replacement switch after pulling that apart and cleaning contacts. Now have to replace in the dash (but I have a full dash cover on so that should be "fun")

Next:

• Hook up headlight wiring upgrade (with relay) and confirm things still work
• Hook parking light wiring upgrade (with relay) and confirm things still work
• Replace Hazard switch

 

So, this leaves me with (not critical but "while the patient is open):

• Blower fan works but is on all the time
• Choke light doesn't work
• Dash lights - some work (speedo, clock) others don't. Maybe ground on those not working?
• Ammeter bad (see earlier - have disconnected and will replace or upgrade to voltmeter later)

What and adventure this has been. And an education! I can't say I want to dive into electrical stuff again, but the person that helped me last night (owns a local shop and is extremely knowledgeable and helpful) helped me better understand things and to feel more comfortable. He's going to come back and help me resolve the rest of the issues so I can put it all to rest.

 

Eventually I'm going to add a fuse block under the hood for the extra power wires I have run to remove all the inline fuses and clean up the look a little bit. But for now, once the above remaining items are resolved, I'm going to start it and hopefully wrap up the rest of the items to get ready for this weekend. Running out of time!

 

MANY MANY thanks for all the input and suggestions. Between the input here and the help of the person last night, much has been resolved and I feel much more comfortable. 

 

Thanks!