The Stovebolt Site Forums The Shop Area The Electrical Bay alternator

recently tried to start my old truck. it has a 250 in it with a single wire alternator. i have had this truck for over two years and have not had any trouble with the electrical system. it has a new battery, which is about a month old. after a week of cold weather the battery is dead so i jumped it off and got it started. when i go to disconnect the jumper cables the truck dies. reconnect the cables and it starts. this happens each time i jump it off. i had the alternator checked and it is good. the guy at the parts store said that the alternator i have is a two wire one. i told him the truck came that way when i got it and has worked for over two years on the one wire. could it be the battery. i am going to have it checked. any thoughts?

It sounds like a shorted battery to me. I had a jeep do that once. It was shorted so bad that it actually stalled out the truck I was jumpering it from.
You can take out the battery and have it tested at an auto parts store.

blkhrn,

It would take a automotive electrical shop to diagnose a shorted diode in the alternator that could allow the battery to discharge. The 'parts store' alternator test isn't comprehensive enough to catch this problem

This subject came up recently in this forum, and the consensus was that after the engine was started, you should be able to remove a battery cable and have things continue to operate.

If you CAN'T do this, and your battery is only two years old, the odds are with a faulty alternator.

If you have a meter, you can test the system at the battery to see if the alternator is charging properly.

If your battery was discharged enough that you couldn't start the truck, you will need to charge it with a battery charger...not the alternator.

Stuart

make sure ALL of your ground cables are solid and good.
disconnect the battery while you make sure the battery is fully charged. re-connect and start the truck. if you disconnect the alt. from the system, does the truck die w/ the fully charged battery?
can or have you had the battery checked where you bought it for a load test? have you taken a VOM and checked the alt.?
>> output should be 13+ volts @ the single post?
if my thoughts are correct...
if the system is all connected and you disconnect the battery it seems the alt is not putting out voltage.

if the battery cheaks good then i bet the diodes are blowen and will drain battery when setting unless you disconect one battery lead everytime you park it thats how i found out my alt was bad it would charge when running but would discharge when setting and that will toast your battery also after going dead a few times

also if you disconect stuff while engine is running it can fry stuff not a good idea desconect battery first before doing anything

My money is on a bad battery. Start the truck and increase the RPMs. Take a screwdriver and stick it up to the rear bearing on the alternator. If it sticks to the rear of the alternator then its charging. You could have a diode out in the rectifier bridge causing some bleed back on the battery but the only true way to tell is with a hi tech alterator testor or test the individual diodes with the alternator apart. I would have the battery load tested and go from there.
Ken

Thanks for all the help. It turned out to be a bad battery. Back on the road again.

IMO I always buy Optima Batteries because they last forever, even fully draining one like I did by leaving the lights on last night. They are the most advanced batteries on the market and worth every penny.

Camo Mike,

Welcome to the Stovebolt. My son drained a Optima battery on his jeep by leaving something on too. As I recall, the recharge procedure was very complicated...almost a situation where you scrapped the battery and bought a new one.

What does the manufacturer say about recharging a totally discharged Optima battery.

Stuart

I just sent a request to Optima for some clarification on how to recharge a dead Red Top. I let mine get almost dead and had a hard time recharging. It kept cycling the circuit breaker on my charger by trying to pull more amps than it could put out. I'll post what reply I get.