I am the happy owner of a Fiat 124 spider from 1979
After replacing a worn out alternator I have problems with power for the ignition
When I turn the key there are no problems with the starter and the headlights, but no power for the ignition.
Since there is no power for the interior light, oil pressure lamp, clock, seatbelt alarm and signal I would expect a broken fuse, but the fuse is ok.
The problem is not permanent sometimes I’m lucky and the ignition and everything works.
Can anybody help me with this problem?
Is it old relais?
I thank you in advance !

Check and clean all of your grounds, particularly the one for the panel lights and gauges - I believe it is a "crown" located under the dash, just to the right of the steering columnn. Clean and apply dielectric grease to prevent future corrosion. Check the ignition switch connector - large plastic connector under the dash to the right of the steering column.
Also, the ignition switch itself may be bad, not uncommon in these cars.

GeorgeT said:

Check and clean all of your grounds, particularly the one for the panel lights and gauges - I believe it is a "crown" located under the dash, just to the right of the steering columnn. Clean and apply dielectric grease to prevent future corrosion. Check the ignition switch connector - large plastic connector under the dash to the right of the steering column.
Also, the ignition switch itself may be bad, not uncommon in these cars.

Click to expand...

Tank you for your help

I followed your advice except replacing the ignition switch, but the result is still no ignition
Can I shortcut some of the weirs on the ignition switch to test if it is a faulty switch?

Nils Toft said:

I would expect a broken fuse, but the fuse is ok.
The problem is not permanent sometimes I’m lucky and the ignition and everything works.

Click to expand...

As the problem is intermittent, it would suggest a poor connection somewhere.

The ceramic type fuses are often corroded at their connection points in the fusebox. On visual inspection they may look OK, but it would be advisable to remove them and clean the contact areas.

As mentioned by GeorgeT, the ignition switch connector could be a likely culprit. They are known for burning inside the connector. You would need to remove the plastic connector to see if any of the metal terminals were burnt.

If this doesn't resolve the problem, you will need to trace each of the affected circuits to find the poor connection.

Here's a copy of the 1979 Spider ignition wiring diagram. It may help. I can post more wiring diagrams if you need them.

I'd be inclined to start with the ignition supply to the coil and fusebox. There should be two pink wires from the ignition switch connector. One goes directly to the coil, the other to fuse #1 in the fusebox. Both should be 12v +ve when the ignition is switched on.
-

Davren said:

As the problem is intermittent, it would suggest a poor connection somewhere.

The ceramic type fuses are often corroded at their connection points in the fusebox. On visual inspection they may look OK, but it would be advisable to remove them and clean the contact areas.

As mentioned by GeorgeT, the ignition switch connector could be a likely culprit. They are known for burning inside the connector. You would need to remove the plastic connector to see if any of the metal terminals were burnt.

If this doesn't resolve the problem, you will need to trace each of the affected circuits to find the poor connection.

Here's a copy of the 1979 Spider ignition wiring diagram. It may help. I can post more wiring diagrams if you need them.

I'd be inclined to start with the ignition supply to the coil and fusebox. There should be two pink wires from the ignition switch connector. One goes directly to the coil, the other to fuse #1 in the fusebox. Both should be 12v +ve when the ignition is switched on.
-

Click to expand...

Thank you for your help

To test the connections I made a weir fitted with a fuse connected directly to the battery +

I then connected it to the opposite site of fuse 9 in the fuse box in order to test the fuse box and the ignition switch and my ignition then works.

My conclusion is that there is no power from the two red cables on the opposite side of fuse 9 or from the “in line fuse”

Could it be the in line fuse that is bad and where is the in line fuse located?

Thanks in advance!

Looking at the wiring diagram above, fuse 9 should already have a permanent 12v +ve supply to it direct from the battery.

If you look at the circuit diagram, F9 is connected to F10 by a busbar inside the fusebox. A black wire goes from the top of F10 to the B+ terminal on the alternator, then to the main starter motor solenoid supply bolt, then via a heavy cable to the battery +ve terminal.

By connecting your test wire to the bottom of F9, you have bypassed this supply.

I'd suggest you use a multimeter to check for a permanent 12v +ve at the top of F9 and F10, then at the alternator B+ terminal, then at the main stater motor solenoid terminal 30.

As the 124 Spider was not very popular this side of the pond and I've not worked on one for at least 25 years, I can only advise you based on the wiring diagrams.