Intermitten battery light
Senior User
Joined: Mar 2006
Posts: 101
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test terminal?
Thanks for the diagram.
In the tests you describe, I am assuming that you mean to use terminal C102c for both. The description of each terminal to use for each test is different.
Is the Instrument cluster smart enough to sense the items that I am testing for? I want to be able to display to Brand X if the unit is sending a faulty signal if possible.
What does the OBD port operate off of that my Dashhawk is seeing >13.2 volts? The instrument cluster? Battery?
'77
In the tests you describe, I am assuming that you mean to use terminal C102c for both. The description of each terminal to use for each test is different.
Is the Instrument cluster smart enough to sense the items that I am testing for? I want to be able to display to Brand X if the unit is sending a faulty signal if possible.
What does the OBD port operate off of that my Dashhawk is seeing >13.2 volts? The instrument cluster? Battery?
'77
Senior User
Joined: Mar 2006
Posts: 101
Likes: 0
test terminal?
Thanks for the diagram.
In the tests you describe, I am assuming that you mean to use terminal C102c for both. The description of each terminal to use for each test is different.
Is the Instrument cluster smart enough to sense the items that I am testing for? I want to be able to display to Brand X if the unit is sending a faulty signal if possible.
What does the OBD port operate off of that my Dashhawk is seeing >13.2 volts? The instrument cluster? Battery?
'77
In the tests you describe, I am assuming that you mean to use terminal C102c for both. The description of each terminal to use for each test is different.
Is the Instrument cluster smart enough to sense the items that I am testing for? I want to be able to display to Brand X if the unit is sending a faulty signal if possible.
What does the OBD port operate off of that my Dashhawk is seeing >13.2 volts? The instrument cluster? Battery?
'77
Hotshot
Joined: Dec 2003
Posts: 15,369
Likes: 121
From: Stuttgart, Ar
Checking Ripple Voltage
Ripple voltage or (AC voltage) can be measured by switching your DMM to AC and connecting the black lead to a good ground and the red lead to the "BAT" terminal on the back of the alternator, (not at the battery). A good alternator should measure less than .5 VAC with the engine running. A higher reading indicates damaged alternator diodes.
Alternator Leakage Current To check alternator diode leakage, connect the multimeter in series with the alternator output terminal when the car is not running. Leakage current should be a couple of milliamps at most; more often, it will be on the order of 0.5 milliamps. Use care when disconnecting the alternator output wire; make sure the battery is disconnected first.
Ripple voltage or (AC voltage) can be measured by switching your DMM to AC and connecting the black lead to a good ground and the red lead to the "BAT" terminal on the back of the alternator, (not at the battery). A good alternator should measure less than .5 VAC with the engine running. A higher reading indicates damaged alternator diodes.
Alternator Leakage Current To check alternator diode leakage, connect the multimeter in series with the alternator output terminal when the car is not running. Leakage current should be a couple of milliamps at most; more often, it will be on the order of 0.5 milliamps. Use care when disconnecting the alternator output wire; make sure the battery is disconnected first.
Lead Driver
Joined: Feb 2011
Posts: 8,241
Likes: 155
From: L.A. (Lower Alabama)
Yes both tests are on the battery "lug" at the back of the alt. I went around in circles with mine a while back and studied and tested and replaced parts, I don't remember if ac on the line will turn the light on, or if it indicates an diode issue that does (in other words how smart the instrument panel is). The tests I posted is just a quick way to check the diodes. Here is a thread with some " theory of operation" info that may help you in your quest. Don't miss the links Blade put up in post #11:
https://www.ford-trucks.com/forums/1...coming-on.html
https://www.ford-trucks.com/forums/1...coming-on.html
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