alternator
Thread Starter
|
Senior User
Joined: Dec 2009
Posts: 261
Likes: 0
alternator
Hi
Am facing a dropping on voltage power . When my truck on the idle the voltage reading 12.2V , but when I turn the HIDs and the a/c plus the a/c fan , the voltage drop to almost 9.5V , Then the transmission starts to slamming the gears
Is it the alternator acting or the Battery Which is new .
I don't have the battery light on the dash but I think the dash light is not working .
Am facing a dropping on voltage power . When my truck on the idle the voltage reading 12.2V , but when I turn the HIDs and the a/c plus the a/c fan , the voltage drop to almost 9.5V , Then the transmission starts to slamming the gears
Is it the alternator acting or the Battery Which is new .
I don't have the battery light on the dash but I think the dash light is not working .
Moderator
Joined: Jan 2001
Posts: 56,995
Likes: 2,741
From: Virginia
The alternator could have a bad diode causing low output, or it might just be the idle speed is too low. Around 12v is ok, it means it's just keeping up, but not charging the battery. What are you driving?
Thread Starter
|
Senior User
Joined: Dec 2009
Posts: 261
Likes: 0
Am driving 2000 Excursion v10 , even in higher rpm it's low reading.
Laughing Gas
Joined: Sep 2012
Posts: 1,100
Likes: 6
From: Georgia
More like shot. Although if you don't have a good ground you'll have low voltage. Make sure that's good, if it is, then yeah, you need your alternator rebuilt or replaced. Have your battery and alternator both tested.
Give this a read. http://www.prestolite.com/literature...leshooting.pdf
Give this a read. http://www.prestolite.com/literature...leshooting.pdf
Thread Starter
|
Senior User
Joined: Dec 2009
Posts: 261
Likes: 0
More like shot. Although if you don't have a good ground you'll have low voltage. Make sure that's good, if it is, then yeah, you need your alternator rebuilt or replaced. Have your battery and alternator both tested.
Give this a read. http://www.prestolite.com/literature...leshooting.pdf
Give this a read. http://www.prestolite.com/literature...leshooting.pdf
Still reading low 12.3 V to 9.8 .
But I didn't got the Dash battery light indicator.
Trending Topics
Moderator
Joined: Jan 2001
Posts: 56,995
Likes: 2,741
From: Virginia
With all the loads you described on, and a low idle, 12.2 would be normal, the alternator is supplying all the loads, but not charging the battery. Lower than 12v, the battery is being discharged. But I agree with no loads and at idle, the voltage should be higher. And the 9v reading is too low. Take the alternator off and let the store test it on their machine.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
3 Best / 3 Worst Parts of Modern Ford Ownership
Brett Foote
10 Amazing Upgrades That Solve Common Ford Truck Owner Headaches
Pouria Savadkouei
Every 2026 Ford Engine Explained
Brett Foote
10 Ugly Ford Trucks That We Still Kinda Love
Joe Kucinski
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
Thread Starter
|
Senior User
Joined: Dec 2009
Posts: 261
Likes: 0
With all the loads you described on, and a low idle, 12.2 would be normal, the alternator is supplying all the loads, but not charging the battery. Lower than 12v, the battery is being discharged. But I agree with no loads and at idle, the voltage should be higher. And the 9v reading is too low. Take the alternator off and let the store test it on their machine.
Moderator
Joined: Jan 2001
Posts: 56,995
Likes: 2,741
From: Virginia
Yes, sorry I missed that in your 1st post. With no loads you should be up around 14v like Rovernut said, with loads you might get down to 12ish depending on the circumstances.
I would take it off and get it checked.
I would take it off and get it checked.
Thread Starter
|
Senior User
Joined: Dec 2009
Posts: 261
Likes: 0
Do you recommend a high output alternator 300 amp and big 3 upgrade. And is there any side effect for this powerful alternator for the ecu and pcm and all other electrical factory stuff.
Laughing Gas
Joined: Sep 2012
Posts: 1,100
Likes: 6
From: Georgia
Electronics are dependent on, and sensitive to, correct voltage. The amperage is irrelevant, as long as it's enough.
If you do go with a high output alternator be sure your alternator to battery cable is large enough. If it's too small you'll have a volt drop during high output. I'd size it so you don't get more than 0.25v drop between the alternator and battery. If the cable is 3' long you'd want a #4 welding cable for a 300a alternator.
If you do go with a high output alternator be sure your alternator to battery cable is large enough. If it's too small you'll have a volt drop during high output. I'd size it so you don't get more than 0.25v drop between the alternator and battery. If the cable is 3' long you'd want a #4 welding cable for a 300a alternator.
Thread Starter
|
Senior User
Joined: Dec 2009
Posts: 261
Likes: 0
Electronics are dependent on, and sensitive to, correct voltage. The amperage is irrelevant, as long as it's enough.
If you do go with a high output alternator be sure your alternator to battery cable is large enough. If it's too small you'll have a volt drop during high output. I'd size it so you don't get more than 0.25v drop between the alternator and battery. If the cable is 3' long you'd want a #4 welding cable for a 300a alternator.
If you do go with a high output alternator be sure your alternator to battery cable is large enough. If it's too small you'll have a volt drop during high output. I'd size it so you don't get more than 0.25v drop between the alternator and battery. If the cable is 3' long you'd want a #4 welding cable for a 300a alternator.
Is it ok to use a normal battery with the high output alternator ?
Thread Starter
|
Senior User
Joined: Dec 2009
Posts: 261
Likes: 0
I do have 6 HIDs 2 big Mercedes a/c fan , 2 head units still in the box ( 7'. Single din pioneer And wide screen jvc ) and am going to install 1000w sub and 600w amplifier.still in the box also. .
Thread
Thread Starter
Forum
Replies
Last Post
1993 ford
Pre-Power Stroke Diesel (7.3L IDI & 6.9L)
4
Jun 16, 2017 04:40 PM
mxfam4x4
1997 - 2006 Expedition & Navigator
15
Mar 5, 2008 10:38 AM
firsttimeford
1987 - 1996 F150 & Larger F-Series Trucks
14
Feb 12, 2005 04:52 PM