Voltages?
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5th Wheeling
Joined: May 2006
Posts: 42
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Voltages?
I have a 03'. At idle everything seems fine, but if you pat the throttle or press it, the voltage goes to 15.3v on my Fluke and comes right back down to normal 13.9-14.2v. I noticed this because my lights would get bright as I started from a stop sign. I'm pretty sure it hasn't always done this. I searched the forum and found similar but not exact problems. The batteries are a little over a year old and the Alt. is 2 months old. do you think this alt. is overcharging? it only does it for a second. Thanks
Post Fiend
Joined: Jul 2005
Posts: 6,127
Likes: 6
Try this thread... see post re high voltage.
https://www.ford-trucks.com/forums/1...and-p1000.html
Note you have nearly the same symptoms as bismic.
Therefore, I say... same suspect.
https://www.ford-trucks.com/forums/1...and-p1000.html
Note you have nearly the same symptoms as bismic.
Therefore, I say... same suspect.
Thread Starter
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5th Wheeling
Joined: May 2006
Posts: 42
Likes: 0
Okay, I followed the thread you mentioned, seems he had battery problems, but did his head lights, dash lights, etc. get brighter for 1-2 seconds after starting from a dead stop or reving the engine while in park? Thats what gets me. I will check my batteries tomorrow as I checked the sense wire, pigtail and relays already as you mentioned in the other thread. Thanks for pointing me in the right direction. He said the ambient temp would cause the 15v, but I don't think mine has ever done this before.
Fleet Owner
Joined: Nov 2003
Posts: 27,915
Likes: 3,635
After changing my batteries out, here is my voltage performance:
12.5V "at rest" - measured w/ a gauge in the power port in the cab
11.8 when cranking (might be less momentarily if I measured the voltage w/ a multimeter on the battery itself)
Slowly and steadily rises after starting
Can go as high as 14.5 to 14.8 w/ alternator supplying power (after glow plugs drop out)
Slowly drops and stabilizes at 14.0 to 14.2
I truly do not think I have an issue w/ the alternator or the sensing wire, but as always, I will continue to watch it.
FYI - The alternator rating from the manufacturer is 14.8V output.
12.5V "at rest" - measured w/ a gauge in the power port in the cab
11.8 when cranking (might be less momentarily if I measured the voltage w/ a multimeter on the battery itself)
Slowly and steadily rises after starting
Can go as high as 14.5 to 14.8 w/ alternator supplying power (after glow plugs drop out)
Slowly drops and stabilizes at 14.0 to 14.2
I truly do not think I have an issue w/ the alternator or the sensing wire, but as always, I will continue to watch it.
FYI - The alternator rating from the manufacturer is 14.8V output.
Fleet Mechanic
Joined: Nov 2003
Posts: 1,372
Likes: 14
From: West Cornwall, CT
A large transient voltage rise with engine rpm could be as simple as a poor connection between the battery and alternator. As voltage tries to rise, the battery just accepts a higher charge rate and keeps voltage down.
If you run the truck with the batteries disconnnected from the alternator, has really poor connection, or if a battery has an internal open, the alternator voltage will act just like you describe. This happened on my '95 F-250.
Lou Braun
If you run the truck with the batteries disconnnected from the alternator, has really poor connection, or if a battery has an internal open, the alternator voltage will act just like you describe. This happened on my '95 F-250.
Lou Braun
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Post Fiend
Joined: Jul 2005
Posts: 6,127
Likes: 6
Lou,
Problem, he replaced both batteries, cables are new, and the voltage is still somewhat higher than before all this happened.
Problem, he replaced both batteries, cables are new, and the voltage is still somewhat higher than before all this happened.
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Fleet Owner
Joined: Nov 2003
Posts: 27,915
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How did you check your batteries? I have a load tester (need to test them unhooked and individually) AND a hydrometer for checking the battery acid density. Even with those tools, it did not identify a bad battery. It did show that one battery was getting weak, but wasn't bad. Then I took the batteries to Interstate (drove the truck there) and they tested them and showed one battery to be bad. Since the batteries were under warranty, I then drove to Ford. They tested them and they both came back as bad.
I guess the point is - verifying a bad battery is not easy.
I guess the point is - verifying a bad battery is not easy.
