No power to gauges

[PilotInASpider]

Here’s my second post in 5 minutes I have a ‘79 Spider that has no power to my gauges or headlights/blinkers. My power windows and wipers work but I get nothing besides that. Everything was working yesterday but would occasionally cut out before that. The power would come back after a bit but now it’s not. I have no idea what would cause this intermittent power to my gauges and lights. My radio and power antenna have never had power since I bought the car. Any ideas on what would cause that to go out? My fuses to the left of the steering column are all fine. Thanks for any help with these gremlins!

[aj81spider]

I'd check your ignition switch. They go bad, and the intermittent operation was an early symptom for me. The wipers and lights come off different ignition switch outputs, so you could have one contact going bad. It's easy to check (meter on the back of the switch).

If you don't have the wiring diagrams you can either download them from Mirafiori.com or PM me your email address and I'll email you a set.

[18Fiatsandcounting]

A.J. beat me to it, but it sure does sound like an ignition switch issue. Try this test: Turn on the ignition (without starting the car) and reach down and jiggle the wires going into the back of the ignition switch and/or gently pull the wiring bundle from one side to the other, up/down, etc. See if the gauges and lights and such come on (or go off).

If that's the case, it could be a bad ignition switch, or if you're lucky, simply a loose connection at the rear of the switch.

-Bryan

[spider2081]

I have a ‘79 Spider that has no power to my gauges or headlights/blinkers.

I'm not sure of your issue. Is it that the gauges are inoperative (they do not indicate) or is is the problem the internal lighting for the gauges does not work? do you have a trouble light or volt meter to make some tests ?

[PilotInASpider]

I have a ‘79 Spider that has no power to my gauges or headlights/blinkers.

I'm not sure of your issue. Is it that the gauges are inoperative (they do not indicate) or is is the problem the internal lighting for the gauges does not work? do you have a trouble light or volt meter to make some tests ?

The gauges themselves aren’t working, along with the headlights/blinkers. They sometimes went out before but came back on after a bit. Today I took out my ignition switch and inspected it. Everything looked fine although it only had four connectors with five spots for connectors. It has a brown wire, two red wires on one connector, a white wire, and a yellow wire. I took apart the ignition itself and it seemed to be working fine. I also have no power to my radio or antenna but that was a problem before. I’m guessing I have to take out most of the trim and go over all of the wiring and relays? Just spent $360 on a carb so I’d like to have this car driving thanks for any more advise!

-Sam

[aj81spider]

I'm not sure that you would be able to tell that you had an intermittent problem with your switch without completely disassembling the switch (and perhaps not even then). It also sounds like your switch has been replaced or at least rewired in the past. According to the wiring diagram I have, the stock wiring configuration of a 1979:

Inputs:
(30) Brown
(30/1) Black

Outputs:
(50) Red (powered by brown in only the start position)
(15/54) Pink (powered by black in the run and start positions)
(INT) Light Blue/Black (powered by brown in the run and start positions)
with two white wires attached to a different part of the switch for the seatbelt interlock chime (which is frequently disconnected).

The way to check the switch is to wait for the problem to happen, then put a meter on each of the outputs and see if you have voltage. The exception to this is (50), which goes to the starter and will only have voltage when you are starting the car (and you will know if that's not working as the starter will not operate).

You should get a wiring diagram and you should check where your non-standard color wires go. Another possibility is that a previous owner put in relays and they go to the relays. If you have relays then it's possible that one of them went bad instead of the switch.

There's a lot of debugging you can do without having to disassemble the interior.

[18Fiatsandcounting]

Today I took out my ignition switch and inspected it. Everything looked fine although it only had four connectors with five spots for connectors. It has a brown wire, two red wires on one connector, a white wire, and a yellow wire.

It sounds like someone has been in there before and done some rewiring (a common occurrence), as the stock wires for these ignition switches are usually black, brown, red, pink, and blue/black. And small white and pink wires for the "remove key" switch.

That being said, if the wires are all going to the right places, the color doesn't matter. But since we don't know how the ignition switch is wired up, my guess is that it's not wired correctly and so you have the odd behavior with the lights and gauges.

In general, the wires' function is as follows (there are variations in model years):
The black wire is a +12V supply line from the alternator
The brown wire is a +12V supply line from the starter
The red wire actuates the solenoid on the starter motor when the key is in the "start" position
The pink wire is one of the main wires to the fuse box, essentially powering most accessories
The blue/black powers the ignition and stuff like the electric fuel pump, and some other accessories.

It sounds like you might have some sleuthing to do to figure out how yours is wired up.

-Bryan

[TX82FIAT]

Sounds like an ignition switch to me as well. I've had a couple of these go bad over the last 30 years and they present in various ways but almost always some intermittent failure before some circuit stops working altogether. About two months ago I installed the ignition switch relay as a precaution measure to prolong the life of the current switch and reduce resistance across the switch.

[PilotInASpider]

Update: power is back! The fuse controlling the gauges and lights was corroded. Everything is working perfectly now. A huge thanks to Mark Allison for helping me with this! I really appreciate all of the replies to this topic. Happy spring to you all!

-Sam