I own a 1985 Bronco 351 2 barrel. I have replaced battery, starter and alternator four times in the last two months. It runs for a few days then I have to jump start. What can this be ... Anyone help?

 

Welcome to FTE

Sounds very much like you have a parasitic or phantom load electrical draw that is running the battery down overnight or whenever the engine is not running. Common culprits generally are aftermarket stereo or other accessories and/or defective rear wiper units, even glovebox lights.

Remember too, a "jumpstart" is strictly a procedure to get you off the highway and back home to safety in an emergency, like a blizzard or whatever. It doesn't replace the need to re-charging the battery with an external unit. The vehicle alternator will not do this (unless you drive to Montana or something like that) and even then it may be well be permanently damaged. As you are probably aware they aren't giving batteries or alternators away just yet either.

Put it on a charger and get it plussed up to 100% and be sure to disconnect it till you figure out for sure what the issue was. Re-connect it to drive to work or whatever. Don't let a battery run down if it can be helped, even just a little.

Measure charging voltage at the battery terminals at a fast idle with headlights on and heater blower on HI, want to see 13.8 to 14.3 volts.

Connect ammeter in series with battery cable and battery post, current draw should not exceed around 50 milliamps. Disconnect fuses or breakers or relays etc, to isolate where the problem is located.