alternator test voltages
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Senior User
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From: Canada,Ont.
alternator test voltages
I have a alternator that is buzzing/humming with koeo
I get battery voltage at all three wires red, og/lb and lg/rd with koeo
With key off engine off battery voltage at the red wire(lug on alt) and og/lb wire and 0 at lg/rd
Im not sure this is right as I found this link https://www.ford-trucks.com/forums/9...or-no-ecm.html that states lg/rd should be around 3 volts koeo but it is for a E series is this the same for a F350 6.0l 2003 single alt
Thanks again
I get battery voltage at all three wires red, og/lb and lg/rd with koeo
With key off engine off battery voltage at the red wire(lug on alt) and og/lb wire and 0 at lg/rd
Im not sure this is right as I found this link https://www.ford-trucks.com/forums/9...or-no-ecm.html that states lg/rd should be around 3 volts koeo but it is for a E series is this the same for a F350 6.0l 2003 single alt
Thanks again
Post Fiend
Joined: Jul 2005
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You got a problem:
Somebody screwed up the wiring... or a short...
See:
https://www.ford-trucks.com/forums/9...ml#post8782374
LG.RD should be 1-3 V with KOEO
8-9V with engine running.
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Senior User
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From: Canada,Ont.
The LG/RD comes from the instrument cluster (10849) and that would be where the 1-3v would come from is there 12v going into the instrument cluster.
There is a lot of wire connections under the dash,pioneer stereo and viper alarm and remote start Im guessing this is where to start, this may be beyond my abilities I guess we'l see
There is a lot of wire connections under the dash,pioneer stereo and viper alarm and remote start Im guessing this is where to start, this may be beyond my abilities I guess we'l see
Post Fiend
Joined: Jul 2005
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Start looking for some tap into the wire by someone looking for a "hot" for an accessory.
Do you know who is the installer for that stuff?
I would start there...
In the good old days, you tap into any available wire and steal the power to run whatever you have (assuming relatively low draw).
But with BCMs, most circuits are now monitored and controlled, and that kind of gaming just don't fly.
If they tapped into the exciter wire of the alternator... that is a sure fire to trip up your alternator.
It expects to see 8 - 9 v with the engine running.
If you totally bomb in figuring it out... a brand new wire that bypass the suspect section is the only game left in town.
I assume you tested the output at the instrument panel and it is to spec....
Do you know who is the installer for that stuff?
I would start there...
In the good old days, you tap into any available wire and steal the power to run whatever you have (assuming relatively low draw).
But with BCMs, most circuits are now monitored and controlled, and that kind of gaming just don't fly.
If they tapped into the exciter wire of the alternator... that is a sure fire to trip up your alternator.
It expects to see 8 - 9 v with the engine running.
If you totally bomb in figuring it out... a brand new wire that bypass the suspect section is the only game left in town.
I assume you tested the output at the instrument panel and it is to spec....
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From: Canada,Ont.
No I do not know who installed anything, only had the truck for a couple of months I have done a fair amount maintenance mechanically to the truck and have had some electronic issues with no answers maybe this will lead me somewhere
Thanks
Thanks
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From: Canada,Ont.
I have found that the indicater bulb is blown in the dash I have read this can cause problems with some vehicles does anyone know if this bulb controlls the field (exciter) wire on these 6.0l
Post Fiend
Joined: Jul 2005
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That will do it.
Fix it. While you are at it... replace every bulb as they are probably all weak / near end of life.
See instructions in link below.
Especially --- beware of the problem with the plastic bulb holders that are aged --- and no longer make proper contact.
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Senior User
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From: Canada,Ont.
Does battery voltage (12v) go into the instrument panel and the low 1-3 volts come out in the field voltage
My bulb is not blown again human error .
https://www.ford-trucks.com/forums/9...ml#post8782374
My bulb is not blown again human error .
https://www.ford-trucks.com/forums/9...ml#post8782374
Post Fiend
Joined: Jul 2005
Posts: 6,127
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Does battery voltage (12v) go into the instrument panel and the low 1-3 volts come out in the field voltage
My bulb is not blown again human error .
https://www.ford-trucks.com/forums/9...ml#post8782374
My bulb is not blown again human error .
https://www.ford-trucks.com/forums/9...ml#post8782374
Yup. For single alternator.
If you have a dual alternator.. NO.
1-3 v engine off, 8-9 v engine on.
Somebody most likely cross wired a live 12v (full voltage) wire to that circuit.
Start fishing...
Post Fiend
Joined: Jul 2005
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Do yourself a favor.
Use live bait.
Do not use cheap lures.
Do it this way ---
Connect a wire to where you are getting the 12V when you should be getting 8-9v Key on engine running. (exciter wire)
If I were to guess, the short is after it comes out of the panel, so even with Key OFF Engine Off, you are still getting 12V
No matter, if not, just turn Key ON, Engine Off.
You know you should be getting 3v under that circumstance.
If you are reading 12
Start pulling fuses until it goes to 3V or zero Engine Off, or 8-9V Engine On.
There --- you have the circuit isolated.
Fish that circuit.
Prime suspect: Idiot installer of some accessory.
Bad news suspect: a chafed wire shorting
Real bad news: internal short of instrument panel
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Senior User
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From: Canada,Ont.
yeah I did the fuse pulling the only one the made a difference was the one feeding the instument panel Im going to apply 12v volts direct from battery to the instument panel at the correct pin(20) and see what my output is at pin 12 I have a bad feeling Im going to get battery voltage