Fuse box ground?

[70spider]

Hello, it has been a minute since I have been here. I have a 1970 spider with a bit of an electrical problem, everything is dead except the head lights (I have an updated relay system) and I can start the car. I noticed the old fuse box had a break in the connection on the 1st position (ground and power wires) so I replaced the fuse box and everything was good until about 10 minutes into the drive and everything stopped working. So i opened the box and it looked like things got a little hot. I disconnected the battery and got my multimeter, disconnected the ground to the fuse box and ohm tested it, nothing but a big fat "1". Does this mean I have a bad ground to the box? And is this the culprit to my problem? Also the wiring diagram shows the ground going to the starter, is this correct? Thanks for any help, electricals are not my strong point.

[70spider]

Update, I cleaned up the fuse box, there was a white oxidized powder on the terminal ends. and put in new fuses and I have electrics again. The test will be to see if a fuse blows next time I run him.

[18Fiatsandcounting]

Sounds like you got it fixed. Just FYI, there are no grounds in the fuse box. All terminals are at +12volts although some are on all the time and some are on only when the ignition switch is in the "on" or "start" or "accessory" position.

-Bryan

[spider2081]

I noticed the old fuse box had a break in the connection on the 1st position (ground and power wires)

I have never owned a 1970 Spider but I have never seen a ground wire connected to a Fiat Spider fuse box. The wire diagram I have for early Spiders shows Fuae 1 internally connected to fuse 2. Is that the broken connection you found? Most Spider fuse panels have the feed side of 2 fuses jumped to gether. The jumper is can be seen looking in to the fuse panel from the fuse side A brass strip can be seen . On most panels fuses 3&4, 5&6, 7&8 are jumped together on the top (feed) side . Some power (battery + ) wires in a Fiat can be black.

I see Dryan responded while I was typing but I'll respond also

[70spider]

On my spider the first position in the fuse box has a black wire, I assumed it was a ground. Tomorrow I will drive the car for a bit and see if I lose electrics again. A bit tricky cause I haven't tagged him in 4 years, I want to shake him down and make sure everything works as it should before tagging it. If it is a short what is the best way to track it down? Should I take apart the harness and inspect all the wires?

[18Fiatsandcounting]

The large black wire to Fuse 1 is the +12V supply from the starter motor to the fuse box. Definitely not a ground despite being black.

As for tracking down shorts, that's a tough one if you don't know where to start. You could certainly remove the two screws that secure the fuse box and look for any frayed wires that are touching, seem to be heat damaged, etc.

What I would do is buy an ammeter (often this function is included in a digital voltmeter) and put it inline between one of the battery connections and its battery post. Not across the battery (that would be voltage).

With nothing turned on, the current draw should be almost negligible, down into the microamps. Pull all the fuses, turn on the ignition and measure again. It should still be negligible current. Then one by one put the fuses back in one at a time and test the functioning of each associated circuit (headlights, horn, parking lights, wipers, brake and backup lights, ignition, etc.) Look for any circuits that seem to be drawing a lot of current. Anything over 8 amps would be suspect.

-Bryan

[Nut124]

I do not believe there is any such thing as fuse box ground.

The fuse box contains live 12VDC circuits that must not touch any ground until the other side of the load.

[70spider]

Well I ran him for about 15 minutes and no issues so far. Thanks for your input.

[70spider]

Update
As anything with this car success is short lived. The dash instruments went out again. This time I can trace it to the #9 fuse. A bunch of stuff run off this circuit; light blue/white wire to the Electrovalve (which I am using for the electric choke at the moment), the double white to the back up switch and and then to the gauges, and the pink one which goes to the 15 pole on the ignition switch. I check the back-up light switch and it is good. So whats my next move? Could the issue be in the gauges or the wires? Back to square one.

[18Fiatsandcounting]

According to my notes, Fuse 9 controls:

Stop lights
Backup lights
Brake warning light on dash
Turn signals
Gauges/Sensors
Cooling fan relay

The pink wire is the "supply" of the the +12V, and the circuits above are the ones that are powered by Fuse 9. I'd test each one in turn to see where the short might be.

-Bryan

[70spider]

Plan of attack tomorrow, physically inspect all wires associated with the circuit. If that doesn't work going to order a SG 25100 Short Tester and go from there.

[spider2081]

SG 25100 Short Tester and go from there.

The term "short" is usually associated with an undesired connection between power and ground or 2 separate circuits.
the term "open" is usually associated with a desired connection not being made.
I feel the issue you described is more likely the loss of power or an "open" circuit. I would start at the battery and check all the connections from there to the fuse panel and ignition switch to cleanliness and tightness.

[spider2081]

I forgot to mention a "short" is often associated with a blown fuse or smoke, melted wires,terminals or connectors. I can't figure out how to edit a post the little pencil symbol in upper right corner is no longer there.

[70spider]

Thanks, I forgot to mention that when I figured out it was the #9 fuse I meant that the fuse blew, and I replaced it and it blew again. I used the multi-meter tool (ohm) and the first wire from the fuse box to the brake light switch is good but from there it becomes an all you can eat spaghetti buffet. I will keep looking for something obvious but I think the short tool will help.

[spider2081]

I forgot to mention that when I figured out it was the #9 fuse I meant that the fuse blew,

In your opening post you stated nothing worked except the headlights and the engine cranked when the ignition switch was in the "start" position. With Fuse 9 blown (open) everything should work except for the circuits fuse 9 protects. I think fuse 9 only has power on it when the ignition switch is in the "start or run" positions. It primarily protects the dash gauge circuits, brake light and turn signal light circuits.
If many more circuits are in op I'm thinking there is more than one issue. Finding the short on fuse 9 will cure that issue. Why other circuits do not have power is probably a different issue.
One over looked issue with early Spiders is a 3 pin connector located in the horn relay ares of the driver side fender well under the hood. This connector has Brown,black and red wires in it. The brown wire brings power to the ignition switch. The black wire brings power to fuse 1 and the red wire brings power from the ignition switch "start" position to the starter solenoid. This connector is often intermittent.