Hello
I want to surprise my bf before he gets back from over seas. He has a 1995 Ford F-350 with the v8 7.5 460,135000 miles and it wont start on occasions, acting like the batts are dead... I have now bought 4 new batteries for the truck, even parralleled 2 optima red tops together and they still do the same thing... Here is the story and i hope someone can help me.. The truck came with 1 battery and then i bought a winch and some lights so i got another batt and parralleled them to bring the amps up so i could run them both... thats it... it will run fine with every thing on and it wont die out.... but as soon as you shut the truck off the batteries act as if there dead...so is it the altuinator?. you can jump the truck to start it and it will be fine.. itll run great with the parralleled batts or with one at 13-15 volts (read off the meter on the dash) but as soon as you shut it off same thing happens.... ive tried un hooking everything..thats the extra lights,winch,big horn and unparalleled the bats so the truck was running on one red top...same thing id jump it drive it for 25 min, shut it off ,go to start it, it would be dead..funny thing is every time i put a brand new batt in it, the truck works great for about 3 days and then it goes back into its old habit.... im really lost please help in time crunch

 

A couple things come to mind.
1. Are you working with one defective battery that is draining the others?
2. Your charging system may be charging only enough to cause the voltmeter to read 13 volts and yet not enough to charge any battery.
3. Do you have hidden corrosion in one or both of the battery cables causing the charging system to think the batteries are fully charged and therefore reduce output.
Once you get the truck running have someone check the charging system to determine just how much the alternator is putting out.
Last but not least , is something staying on and draining the battery(s) when parked?
Let us know what you find.

 

It sure sounds like an alternator issue. Did this only start after putting in the second battery? Leaving something on will drain the batteries, but if you're driving, they should remain charged and the truck should start immediately after turning it off. New batteries lasting only 3 days leads me to think they just aren't getting a charge while running.

 

i work in the diesel industtry we've run into the altenator running the battery done if the regulater is defective

 

I'll give it a try.

A 460 with 135K miles on it can draw up to 300-350+ amps to start. It then takes a minimum of 45 minutes at an engine speed of 45MPH to replace the amperage drawn from the battery to start the engine. Numberous starts and short trips will draw a battery down in short order.

Heck, my 4.2L V6 draws about 275 amps on start-up.

Anyways, this is the way I would proceed (need a digital volt meter and amp meter).

1. Get a digital volt meter, disconnect the batteries from each other and measure their respective voltages. A good battery at rest should read about 12.15 volts.

2. Leave only the original battery connected and start the engine. The voltage should read 13+ volts.

3. Next test the alternator with the engine running by turning all lights on, high beams, A/C, heater and place the fan on the high setting.

4. Voltage should go up to about 14.5 volts and stay there steady. As the battery is being recharged, the voltage will slowly go down to about 14 volts and stay steady.

5. If this is the case, then take the amp meter and clamp it around the alternator output wire and measure the load. OEM MAX output would be 95 amps unless the truck came with the optional OEM 130 amp alternator or was replaced with another output rated unit.

6. Would need to know what the output amps are to determin if the alternator is putting out like it should. The charging voltage can be correct under load, but the alternator may not be putting enought amps out to fully charge the battery(s) in the normal amount of time.

7. Being that you have the same issue with either one or both batteries connected, I would suspect that the alternator is not outputting enough amps when charging.

8. Then again, you may have a parasitic drain on the battery(s) when the truck is turned off.

9. This is checked by turning everything off, then turn the engine off. Put the amp meter on the positive lead off of the battery to see if there is any amp draw. A 15mA draw would be normal for the CPU at sleep.

Hope some of this helps to locate your problem.