Total lack of power (intermittent)

[MMRMVA]

1978 Spider 124, battery in trunk.
I have lost all power 3 times now, and then after just sitting there for ~30 minutes, it comes back.

When in the "no power" state: brand new battery is testing normal. I do have power at the alternator (direct from battery). The interior light by the stick shift is off and the horn does not work, both of which do not need the ignition switch in the "on" position to work. So something is shutting everything but the direct battery connection down.

1st time - while setting the timing, I must have hit something with the clamp on the alternator, sparks flew and then no power. Once it came back it was not an issue for another a week
2nd time - today was doing some tuning at idle, tachometer went bonkers, so I had disconnected the distributor to look in there, forgot to reattach the coil, tried starting it, obviously did not start, lost all power. Maybe the coil wire was touching something, I do not recall.
3rd time - after it came back from 2nd time, would not turn over, testing the coil spark (had spark), then cleaned up some of the distributor connections. Turned over on first crank, ran for a couple of seconds and then lost all power again. I left it alone, but disconnected the battery just in case.

No signs of a burning / melted wire. No smoke, no smell. It is almost as if a safety switch it being triggered, but I have no idea what or where that would be. And time seems to correct the issue.

Any ideas?

[18Fiatsandcounting]

I hope someone else offers their thoughts, but here are mine. It sounds like you might have an intermittent connection with the brown wire between the main post of the starter motor solenoid and the rest of the car electrics.

Right below the brake master cylinder, there should be a 3-pin connector that is often a source of woe. At least if I'm correct for a '78 model. In this 3-pin connector, there are 3 wires: A red wire from the ignition switch to the starter motor solenoid that engages the starter motor, a black wire that runs from the main post of the starter motor solenoid to the alternator output post, and a brown wire that runs from the main post of the starter motor solenoid to the fuse box. Since you have +12V at the alternator post with the engine off, it sounds like that black wire is OK. However, if the brown wire has a connection issue, most of the car's electrics will be dead.

So, check that connector and see if you get +12V on the brown and black wires on the connector that leads to the starter (the other half of the connector will read zero volts on all 3 wires when disconnected). Engine off but battery connected. Wiggle the wires around and see if the +12V on the brown and black wires is steady.

I'd also check the terminal connections on the bag of the ignition switch. Sometimes these loosen up and weird things happen.

-Bryan

[18Fiatsandcounting]

I looked at a wiring diagram for a '78 spider, and my description above may not be totally correct. I believe there is only a 2-pin connector leading from the starter motor to the driver's side firewall, with a brown and red wire. I think there are two separate black wires, one leading from the output post of the alternator to the main +12V connection to the starter, and a separate black wire leading from either that alternator post, or the main +12V starter connection, to the fuse box for fuses 9 and 10.

Fuses 9 and 10 power the horn and cooling fan, and the courtesy lights and some other items. So, if you get +12V on the alternator post, check also that fuses 9 and 10 also have +12V on them (from the second black wire). Fuses 9 and 10 should be powered whether or not the engine is on, and the ignition switch can be in any position.

So my guess at this point is that you have an intermittent problem with the brown wire (to the ignition switch) or the black wire to the fuse box. Or both. Or their connections. Each model year is somewhat different, and most of my knowledge applies to the early spiders and not always to the later years.

Hope this helps.
-Bryan

[MMRMVA]

Thanks Bryan, I think you nailed it.

https://photos.app.goo.gl/cCCiaBkb75bCZYQ47

I checked volts at the alternator and at this device. Then I wiggled wires and tightened everything down. I think the culprit was the back post of the alternator, the nut had come a little loose. Power is back on. I was able to start her up, but it is rainy and cold here today so no further work.

Cheers!

-Matt

[18Fiatsandcounting]

Awesome! But hold on, bro'. What is that part in the picture? I don't recognize it from a spider, so are we talking about a '78 sport coupe (the hardtop version)...? Or did someone add this part to your car?

-Bryan

[MMRMVA]

Spider, soft top. I guess it was added then? Interestingly, Ralf hooked me up with some old images from his database, and this was from a 2005 eBay posting, it looks like a very similar part, but not exactly. So it or something like it has been in the car for awhile.

https://photos.app.goo.gl/ENFZrC2AStaJda1b8

[18Fiatsandcounting]

That spot on the firewall is roughly where the old style external voltage regulator used to be mounted, but after 1977, Fiat spiders came with an alternator that had an internal voltage regulator. So, your spider didn't (shouldn't) have an external regulator, but maybe someone used the mounting location to install some sort of switch, relay, junction box, whatever. It kinda looks like an old electrical part for a 1950s/1960s Ford or Chevy. Whatever it is, the wiring and crimping connectors are not stock.

Nothing wrong with that. If you have a chance, I'd be curious to see where those three wires go. Two red, one green. Maybe an anti-theft kill switch for the car's electrics?

-Bryan

[MMRMVA]

Hey Bryan,
I had been sick for a few days, not messing with the car.

I texted you this picture as well. https://photos.app.goo.gl/FoabGtsubL6msBHh6
1 - red goes back through the firewall with a number of other wires, have not chased it down
2 - red goes to the starter assembly, wired into a brown/orange wire
Green on the right of that 3-wire thing is coming from the alternator

Car would not turn over today, I was going to mess with the points gap on the dizzy, but this led to other electrical testing and led me to the ballast resistor. I am wondering, can the ballast resistors can just fail? After trying to start the engine, the ballast was very hot to the touch. I tested voltage, I get 11.8v going into the ballast, and only 5.3v coming out. https://photos.app.goo.gl/aQctjfRnVMsR2RoJ7.

I then only get 5.1v into the coil itself. https://photos.app.goo.gl/UjTf6t6YEkxYM5or6

I tested ballast and the ohms across the unit at it read 2.0. I am now confused. I've read this is in the correct range, but I am losing too much across the ballast, I should be getting 9v out of the ballast, right?

Can I bypass the ballast resistor to at least test if that is the problem?

-Matt

[18Fiatsandcounting]

Can I bypass the ballast resistor to at least test if that is the problem?

Ballast resistors don't usually fail as they are essentially a power resistor that either measures close to the stated resistance or totally open (in which case it's bad). They are fairly beefy to be able to dissipate the heat due to the current flow, which is an amp or two when the points are closed. The power dissipation for a resistor is the square of the current multiplied by the resistance, so that would be 2 amps squared (4) times the resistance (2 ohms) which would be a power dissipation of 8 watts. Which is why they get hot.

The function of the ballast resistor is to limit the current through the points and the coil. Without the ballast resistor, the points and coil have a pretty hefty current passing through them (2 amps) which is enough to eventually burn up the points or coil.

To answer your question above, yes, you can run without the ballast resistor for a short time (for testing purposes), but it's there for a reason.

Not to throw more automotive stuff at you, but have you measured the dwell angle of the points? This requires a dwell meter which isn't all that expensive, but it does require the engine to be running. Dwell angle for Fiats is either 55 degrees or 60 degrees, depending on model year. I believe a '78 spider is 55 degrees. The dwell angle is actually the degrees of distributor rotation when the points are closed. Since your car is a 4 cylinder, each cylinder has 90 degrees associated with it (360 divided by 4), in a crude sense. If the points were closed all the time, your dwell angle would be 90, and if they were open all the time, the dwell angle would be zero. A dwell angle of 60 degrees would mean that the points are closed two-thirds of the time (60 divided by 90).

At this point, you are probably thinking, "Man, this 18Fiats bozo keeps tossing weird math stuff at me! Why won't he just tell me how to fix my car??!!"

-Bryan

[MMRMVA]

Thanks. This car is a mystery. I disconnected the coil, tested that and it seems with spec. Cleaned up the connection points on the wires, put it back together and it fired up on the first try. Now reading 9.5v on the out side of the ballast.

Now onto the original plan for the day. I will go grab a dwell meter and give that a shot. Thank you. Reading up on the procedure now.

Matt

[MMRMVA]

So I picked up a Performance Tool Multimeter Model: W2972 at the local auto parts store. Nothing fancy, but it claims to test dwell angle. I set it up, turned it to 4 cyl and before hooking it up, it defaults to 90. I hooked the red clamp to the green wire from the dizzy and black to ground. Start the car and the reading drops, for a half second shows something between 90 - 0, and then sits at Zero. That is impossible, right? Then I tried it to the negative post of the coil, and ground...does the same thing. It is hard to find much online about these digital meters, but I have found some evidence that maybe "there are times when electrical noise in the engine compartment is so high the Digital Meter stops working" or others that just claim they are junk.

Has anyone had luck with these?

[18Fiatsandcounting]

I don't have any experience with this particular meter, or digital dwell meters in general, but my guess is that the dwell signal is bouncing around a bit and the electronics of the meter don't know how to interpret this (what value to display), so it defaults to zero. That's one problem with digital multimeters is that they sometime go goofy with unusual electrical waveforms that they aren't expecting.

Do you have another car you could try it on? It would have to be a car with points, but maybe you or one of your buddies has an old-school 60s or 70s Chevy or Ford?

One last thought: You do have the leads plugged into the meter correctly, yes? Black to the COM input, and red to the input on the far right for volts, diodes, dwell, etc.

-Bryan

[MMRMVA]

Lead wires are in the right spot. My buddy next door has a ‘68 Volvo wagon, but with a very non-stock engine in it. Ha.

Your logic on the bouncing around makes sense. Digital is not always better.

[davidbruce]

It kinda looks like an old electrical part for a 1950s/1960s Ford or Chevy.

That looks like a Ford style starter solenoid. They used a remote solenoid on some engines.

1 - red goes back through the firewall with a number of other wires, have not chased it down

I have seen these solenoids used as a anti theft device. When 12 volts are supplied to the small terminal the contacts between the 2 large contacts closes. Power would come from a toggle switch hidden under the dash or something similar. Do you have 12 volts to the small terminal with the ignition switch off? If not, what about in the start or run positions? 12 volts at the small red terminal should = 12 volts at all terminals. With large red going to brown and green going to the alternator it appears the solenoid interrupts the power(brown wire to 30 on the ignition switch). If you have 12 volts to the small terminal but not to the large red terminal I would say this solenoid is faulty. I believe not all of these solenoids are rated for continuous duty. If no power to the small red terminal then you need to trace where it's power comes from and rectify that.

[spider2081]

Keep in mind that the ignition points are usually closed (when the engine is not running)completing the circuit from the battery through the ignition switch through the ballast resistor through the points to ground. When the points are closed there will be a voltage difference measured as you have at the ballast resistor. One side should measure close to battery voltage and the other side of the ballast resistor will measure approximately 3-4 volts less. This indicates a correctly working circuit.
I agree the non standard solenoid in your photo resembles a solenoid used on some Fords years ago. It's function in your car is any one guess and would need some testing to figure out.