I have a 1995 ford f-150 XLT 2WD 2 door with a 4.9L 300ci inline 6.
The battery always goes dead while the truck is running and I have already checked the fuses and everything else. My cables and wiring aren't the best but they should still be able to do their job.
I have just replaced the alternator and the battery STILL goes dead while the truck is running.
I just checked every fuse and relay in the truck and nothing is blown.
I am picking up a brand new battery today because I am convinced it is shot. Will this solve the problem?
I put my battery charger on the terminals (not charging just watching voltage levels) while the truck is running and the volts would go up one volt and down 3-4 volts and this would continue until the truck dies.
It falls down to 11.2 volts
OK that's the important bit.
11.2 V is too low. So either the alternator is bad or the wiring. Now you need to probe the voltage on positive post of the alternator.
I just bought a brand new alternator and a brand new battery.
The voltage still reads very low but it holds a charge now
the volts would go up one volt and down 3-4 volts and this would continue until the truck dies.
but what is the actual voltage on the battery?
What is the voltage on the positive post on the alternator?
What do you mean by that?
How do I test that
what do YOU mean? I'm asking the voltage.
I highly doubt the battery only has 4 volts in it.
When I start the truck after I have charged the battery, the new alternator is charging it up one volt and then the voltage slowly falls down 2-3- or 4 volts and the cycle repeats until the truck dies.
I need help, I'm 15 and trying the best I can
It's a 12 volt battery
It falls down to 11.2 volts
I tested the battery with a multimeter with the truck running and it came out at 25 volts.
25V is WAY too high. It shouldn't go higher than around 15V. The alternator is bad.
It falls down to 11.2 volts
Your battery doesn't need to be replaced at this voltage. If it went down to 8 volts, then you'd replace the battery. Did you check the wiring between the battery and alternator?
Yes
What's the situation like? Does the wiring need replacing?
Maybe, I'm not sure
I just put a new alternator and a new battery in my truck.
My battery will now hold and accept a charge but reads very very low on the instrument panel.
I tested the battery with a multimeter with the truck running and it came out at 25 volts.
I also tested the alternators positive post with the truck running and it came out to be the same as the battery was reading.
Like I said though, the instrument panel reads the battery is very very low, but the multimeter said it is not.
I tried 3 different instrument panels that I had laying around and it was the same on all 3.
The truck starts fine, runs fine, and all of the electronics work as far as I can tell.
I checked every fuse and nothing is blown.
How do you check a relay?
Trust your volt meter. Not the dash readings.
At 25V, you might damage some sensitive electronics, if any. The computers will have regulators to isolate from the 25V, but the regulators have max voltage limitations.
Is the voltage regulator internal to the alternator or external? If it's internal, you changed it already. If external, you might try changing it. It almost sounds like it thinks the battery is low. so the current from the alternator is at max. When that happens, the battery voltage can start rising until the battery can't take any more charge. Then it might explode? Not sure. Maybe the fluid/acid just bubbles?
