Truck has started lower the last couple days so I decided to check the batteries. It's a 1997 7.3. I'm getting 12.2v with the truck off and 11.8v with the truck running. That's after letting it run for several minutes in the high idle tune. Should I be looking more into the alternator? What's the best way to check output?
Mauser48
To start with your battery resting voltage is way too low. A good battery with a full charge should be 12.7 volts or more. 12.2 volts I am surprised it even started.
First unhook the batteries then charge the batteries for several hours.
Let the batteries rest unhooked for a few hours and check them. They should be about 12.7 volts.
Hook them back up and verify the voltage is the same as when they are unhooked.
Start the truck and check the voltage on the batteries. It does not matter which set they should read about 13.8 give or take a bit. If not your batteries are not charging and you should check the post at the alternator. If the post at the alternator is not 13.8 give or take a bit your alternator is not putting out. If it is 13.8 volts it is likely the fuse link from the alternator to the batteries.
When checking the output voltage let the truck idle for a few minutes to stabilize. Also remember the alternator is for toping of the batteries not recharging them after a deep discharge. You can do damage to the alternator trying to bring the batteries back up from that far down.
Let us know what you find.
First unhook the batteries then charge the batteries for several hours.
Let the batteries rest unhooked for a few hours and check them. They should be about 12.7 volts.
Hook them back up and verify the voltage is the same as when they are unhooked.
Start the truck and check the voltage on the batteries. It does not matter which set they should read about 13.8 give or take a bit. If not your batteries are not charging and you should check the post at the alternator. If the post at the alternator is not 13.8 give or take a bit your alternator is not putting out. If it is 13.8 volts it is likely the fuse link from the alternator to the batteries.
When checking the output voltage let the truck idle for a few minutes to stabilize. Also remember the alternator is for toping of the batteries not recharging them after a deep discharge. You can do damage to the alternator trying to bring the batteries back up from that far down.
Let us know what you find.
I charged both batteries separately and then let them rest. Both held about 12.7v. Connected each battery and tested individually. Both had the same voltage connected and unconnected. Started the truck and checked voltage at the batteries. 12.4v. Checked voltage at the alternator post. 12.5v.
Good
Now you know how to troubleshoot and narrow down the issue before pulling the component off the truck. Keeping the batteries charged up is important especially since we are approaching colder weather and the systems will demand more for starting that truck when cold. It was 42 here in the Fort Worth area this morning but that is not cold for the truck yet.
Now you know how to troubleshoot and narrow down the issue before pulling the component off the truck. Keeping the batteries charged up is important especially since we are approaching colder weather and the systems will demand more for starting that truck when cold. It was 42 here in the Fort Worth area this morning but that is not cold for the truck yet.
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