Radio, horn stop working then car won’t start

[Fiatsun1]

I have a 79 spider that starts right up and runs great until recently. I was driving and the radio started to sound out of tune and then stopped working. I stopped for gas and when I went to start it I got nothing. Left it over night, came back next day, it started right up and radio worked.
Drove it today and the radio and the horn stopped working. I stopped to pick up food and when I came out nothing, dead. I am going to let it cool down and try it later tonight. Checked all fuses and they are ok.
Thanks!

[azruss]

I would start with disconnecting the radio to make sure you don't have an internal short thats pulling down the battery.

[Fiatsun1]

Thanks! I did that and nothing. Checked the battery today and it was low. It is a new battery. Battery light on dash stopped lighting but oil still does. Long story short it looks like a problem with the alternator or the wiring to the alternator. I am continuing to problem.

[spider2081]

I think a 79 Spider has a Bosch alternator with the voltage regulator on the back side of the alternator. There is a small diameter push on terminal, black/violet wire connected to the alternator. Remove that waire and connect it to ground then turn on the ignition switch. the batt warning light should lite. if it does not that could be tyour problem. the bulb could be defective or the lamp fell out of its holder. In any case the light circuit excites the alternator for it to start to charge.

[Fiatsun1]

Thanks! I will try that tonight and let you know!

[Spider951]

You may have a clue when you say the battery light does not come on. I was having a somewhat similar problem: battery would run down, alternator not charging (??). After replacing battery and alternator, still the same problem. Eventually I noticed the dash light for the battery/charging (I think it is a blue one on my '81) was also not working. I removed the small light bulb - it tested bad and yes it was just the bulb not a wire issue. Simply replaced the bulb with a new one and suddenly the alternator charges great and no more dead battery. My $1.95 EE degree from the drug store really paid off.