About 2 hours into a roadtrip, all the lights (brake light, parking light, etc.) came on and we figured the alternator was about to go out. Drove about 20 more miles and the radio died and sure enough so did the car like we expected.

 

The next day when we came back to retrieve the vehicle via tow, the car started up just fine (even though the day before it was so dead we couldn't even turn on the hazard lights). Not wanting to risk it we had it towed back.

 

The car is running but I'm afraid to drive it anywhere. I had the alternator and battery both tested at two different shops and they are working perfectly. Checked the cables and connections for corrosion but everything's fine.

 

However, all the lights are still on that came on prior to the car dying. The car is too old to hook up to diagnostic.

 

Any thoughts?

Perhaps the battery cable was loose, or the alternator output wire is going bad. doule check the output wire, and also the skinny withe on the positive battery where it goes to the fuse panel under the dash.

 

Perhaps the alternator failed temporarilt. maybe it overheated. IF the alternator is unusually warm, replace it.

and turn off the radio next time.

Bad connection somewhere. Often a drained battery (that's still good) can rebound after sitting. It will still need a thorough charge, but that fact that it started the car says the battery is in decent shape.

 

Check the ground cable at each end.

Check the alternator output lead where it meets the fuse box. Check the lead that runs from the battery positive to bottom of the fuse box. Those may attach to the same lug under the box, I don't remember exactly.

alternators can, and do, fail due to heat, and it is very difficult to replicate when testing.

 

I had one do this on my 90 Legacy wagon a while back - could drive for a little while and it would be ok, then suddenly the dash would light up. I could pull into the parts store with the symptoms happening, get the guy out there, pop the hood and it would test out fine...the minute the hood was opened, engine heat would escape, the alt would cool off and, for testing purposes, it was fine.

Close the hood, drive away, and within 15 minutes it would show the same symptoms again.

 

I replaced that alt with a rebuilt stock unit, gave the battery a good charging, and havent had a problem since

If the Warning lights are on that means the "charge" light ciruit of the alt.  (which also excites the feild) is open.  Not working.

 

So......If the Alternator bench tested as good......then I would guess the "charge" fuse is blown........or the connector for that wire is poor.

 

The problem is definately the Alts. charge cicuit if all those lights are on.

 

Check the fuse first.....could be that simple.