Went to start my reliable 86 yesterday and got nothing. Faint security light, but no attemt to start, no radio no nothing.

Charged battery overnight, metered to 13v today. But when I tried to start... same as yesterday..nothing.

Is there a master relay or something easy to check?

 

No master relay. Almost all the electrical power goes through the ignition switch which has three contacts. You may have a defective battery or poor cable connections to the battery teminal. I would first remove the battery cables (neg first) and clean the cable lugs, battery posts and the bolts and replace the cables (neg last). Also monitor the battery voltage when you hit crank, the voltage should not fall below 9.0 volts during cranking or your have a discharged battery, poor cable connections, or the battery is at the end of its life. You can tell the state of charge in the battery by measuring its no load voltage. 12.0 volts and lower, discharged, charge your battery up with a battery charger (you already did this). 12.9 volts and higher, fully charged and linear in between. One type of battery failure is high internal resistance and you can check for this by measuring the battery voltage at its terminals and turn on the headlights, normally the voltage drop will be so small, you likely can't see it on your voltmeter. The ignition switch is fed by a fusible link and this link may be blown or defective. With a charged battery and the ign sw in run, you should be able run lights, radio, heater fan, courtesy lights etc. If the fusible link is open circuit, no power will be available for accessories, if it has resistance, you will see normal battery voltage but low voltage on accessories. Proof is measuring the voltage drop across the fusile link with a current load, like having the headlights on. Same for the ign sw contacts, measure the voltage across the ign sw contacts with a load on, like the radio, courtesy lights, headlights.

 

Thanks for the reply.

I think the battery is shot, won't hold a charge. Maybe the alternator is gone too. $$$$$

 

Batteries and alternators don't last forever!