alternator problems
Thread Starter
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Cross-Country
Joined: Jun 2012
Posts: 85
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alternator problems
hey guys i have an 86 ford f150 300 six...and i put another alternator on and it will run with the terminals off the lights are bright but the battery still goes dead after you start it about 10 times.....and it will not charge the battery if roll started...any one know what could cause this....
Senior User
Joined: Dec 2014
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I'm sorry, but your post is very difficult to understand and I am not sure what all conditions you are describing.
That said, if you know that the alternator is known good then you might have a faulty regulator. One major (first to do) diagnostic checks on the charging system would be to look at the voltage between ground (chassis) and a hot wire. You should be expecting it to be 13 or 14 volts while the truck is running.
That said, if you know that the alternator is known good then you might have a faulty regulator. One major (first to do) diagnostic checks on the charging system would be to look at the voltage between ground (chassis) and a hot wire. You should be expecting it to be 13 or 14 volts while the truck is running.
pedant
Joined: Jan 2008
Posts: 23,576
Likes: 40
From: EXTREME southwest CT
Do you have an external regulator mounted on the fender, or an internal regulator with two plugs on the back of the alternator?
If it is a 2G alternator it could be the fusible link or the charging plug itself.
If it is a 2G alternator it could be the fusible link or the charging plug itself.
Thread Starter
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Cross-Country
Joined: Jun 2012
Posts: 85
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Sorry guys...it has a internal regulator...I checked the terminals not running...11.5''''running ..14.68.....the hot wire was 14.68.....I guess it's charging....but if I shut it off a few times it kills the battery. Plus my volt hand does not work......
pedant
Joined: Jan 2008
Posts: 23,576
Likes: 40
From: EXTREME southwest CT
11,5V is a dead battery.
Disconnect the charging lead's fusible link from the starter solenoid and test it for continuity to ground.
It is entirely possible to have a faulty diode and still be charging.
According to Ford's TSB 96-21-04 you should change the charging pigtail any time the charging system is serviced,
After the second time mine went out (taking the battery and the alternator with it) I did away with the "Fire plug" harness harness entirely and upgraded to a 3G.
Disconnect the charging lead's fusible link from the starter solenoid and test it for continuity to ground.
It is entirely possible to have a faulty diode and still be charging.
According to Ford's TSB 96-21-04 you should change the charging pigtail any time the charging system is serviced,
After the second time mine went out (taking the battery and the alternator with it) I did away with the "Fire plug" harness harness entirely and upgraded to a 3G.
Thread Starter
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Cross-Country
Joined: Jun 2012
Posts: 85
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Ok guy it's like I can charge the truck over night and as I drive it through the day every time I have to start the truck it cranks harder till the battery finally won't start the truck......now the wire coming from the starter solenoid has 14.68 volts.....Is that right....I cut out the disposable link.....where is the diode and how does it work......and if I have power going into the starter solenoid won't it charge the battery....this crazy...I can take the terminals off the battery and it will run....but if I turn on the lights it dies......maybe I shouldn't do that....Lol.
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pedant
Joined: Jan 2008
Posts: 23,576
Likes: 40
From: EXTREME southwest CT
The diodes (triode actually) is inside the alternator.
It acts like a one way valve for electricity.
No, don't disconnect the battery while running.
It's bad for the whole charging system
It acts like a one way valve for electricity.
No, don't disconnect the battery while running.
It's bad for the whole charging system
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pedant
Joined: Jan 2008
Posts: 23,576
Likes: 40
From: EXTREME southwest CT
A bad diode?
The battery would discharge through the alternator whenever the engine was off.
You need to test with a meter or test light.
That your engine dies when you turn the lights on makes me think you have a bigger problem.
The battery would discharge through the alternator whenever the engine was off.
You need to test with a meter or test light.
That your engine dies when you turn the lights on makes me think you have a bigger problem.
Cargo Master
Joined: Mar 2008
Posts: 2,573
Likes: 207
From: Washington
If the ALT brushes or diodes are worn/bad it can limit the ALT output and thus slowly drain the battery.
Check the voltage again ... first no load, then with headlights + heater fan on high + plus anything else you can turn on.
If the voltage drop off under high load the ALT is bad.
Jim