Electrical issue - battery tests fine but won't start without a jump, amp light on

[basssque]

So after dropping in the 96 f-150 donor 302 into my 92 bronco something strane occurs. I can't start the engine without jumping it and the amp light on the dash is always lit. If I jump it I can start it again within a short while but if I wait overnight it won't start. I thought it was the battery but I brought the dura last gold which is less than a year old to the store I bought it from, they put it on a machine and it tested good. The new engine has a cam or crankshaft sensor on the front that my wiring harness didn't seem to have a connector for and it also has a single wire alternator opposed to the old alternator which had 2 connectors on it. I believe I wired the alternator right, it was pretty self explanatory. Does anyone have any idea what may cause this or how to troubleshoot it? Thanks

[TheUnforgiven]

you should have swapped your 92 alternator and other engine parts (intake, sensors, etc) over to the 96 engine because the harnesses are not the same (as you've found out). Put the 92 alternator back in it, or make the 96 work properly (i think that's a 3g). there's TONS of information here how to wire a 3g properly, and to verify if you actually have a 3g.

So if the battery sits overnight it goes dead? Sounds like a voltage draw. Make sure the terminals/posts are clean and that the cables are good. Check for a power draw by putting an ammeter in series with the positive cable and terminal. anything more than a half amp-1 amp is a parasitic draw and needs to be corrected.

OR, take that battery to a different parts house and have it tested. I work for Advance and we junk A LOT of duracrap batteries.

[jermil01]

Originally Posted by TheUnforgiven

you should have swapped your 92 alternator and other engine parts (intake, sensors, etc) over to the 96 engine because the harnesses are not the same (as you've found out). Put the 92 alternator back in it, or make the 96 work properly (i think that's a 3g). there's TONS of information here how to wire a 3g properly, and to verify if you actually have a 3g.

This..or you could wire your existing harness to accept the 3G alt..

[Steve83]

There's no difference in the TRUCK ends of 2G & 3G harnesses; only the ALT ends, and it's easy to convert the 2G end to 3G by crimping a ring onto the 2 heavy wires in the big connector.



But it's even easier to connect the '93-96 3G harness to a '92 truck's harness & starter relay.




More importantly: the alt isn't necessary for the battery to work & crank the engine, but you might have a draw that's killing it. After fully charging it for SEVERAL hours, DISCONNECT the battery overnight. If it still won't crank in the morning, it's junk.

The store that your DuraCrap Gold came from is the zone, right? I wouldn't trust them to test a flashlight battery; much less a vehicle's. If it came from WalMart, they're not a whole lot better. Charge it FULLY with a 110V charger overnight, and then take it someone with a MidTronics high-frequency tester.



When it fails, take it back to "the store" for refund, and go buy a decent battery: MotorCraft, Interstate MTP, or Sears DieHard Gold.

BTW
You don't need the misfire sensor on the front of the engine, or the special harmonic balancer with the 4-tooth tone ring. Someone who DOES need them will probably pay you more than a common balancer costs, so help a Bronco brother out and consider putting that balancer up for sale. You don't have to remove it until you get the money and buy the replacement, as long as you explain the delay to the buyer beforehand.

[basssque]

Figured this one out. It was a leaky coolant hose that attached under the throttle body. The coolant was leaking down the hose onto the alternator causing a short. Threw a new hose and clamp on and everything is normal now.