Truck Down Alternator problem.
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Junior User
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Truck Down Alternator problem.
I was on my way home from work Friday and my battery light came on and the alternator was overcharging. I stopped and shut the truck down and pulled the plug out of the alternator so it wouldn't burn anything up. Got it home without running out of juice and never got back to it till tonight. Fired the truck up and checked the output on the alternator and it was 12.4 shut the truck down check the battery 12.4 finally start her back up and check the two wires that plug into the alternator,,, here is the wierd part,,, one tested 11.2 the other 12.2 checked it several times and it was the same each time I had a reman alternator in the shop, swapped it out and no luck,,,, Any Ideas,,, I am in trouble with the wife now cause she is out a car tomorrow with the truck down,,,,
Thanks for any info fellas.
Thanks for any info fellas.
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Joined: Jan 2002
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Test them both
Sounds like your original alternator is bad and your re-man may not be good either. Take them both by an auto parts store for free tests. Once you know that you have a good alternator, you can troubleshoot from there.
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They are telling me that the new one is good however warranteed it and gave me a new one. Love my parts guys.
So at least I know the alt is good.
So why the variation in power at the plug where the field wire and other (can't remember what it is called) come into the alternator? exactly 1 volt diffrence?
Parts guys (also run a garage) said I had to wait 10-15 min fter the glow plugs go out to get a proper test on the system? Seems like the alt would either put out juice or it wouldn't??
So at least I know the alt is good.
So why the variation in power at the plug where the field wire and other (can't remember what it is called) come into the alternator? exactly 1 volt diffrence?
Parts guys (also run a garage) said I had to wait 10-15 min fter the glow plugs go out to get a proper test on the system? Seems like the alt would either put out juice or it wouldn't??
Posting Guru
Joined: Aug 2008
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From: No.Va.
The glow plugs are a very big draw on the elec. system.
Waiting until they finish, will give you a more accurate reading of the alt.
(on my 06,I can tell when the glow plugs go off at night because the lights get brighter)
That's actually very good advice from the parts guy.
( I don't wait 10-15 min.,just until the glow plugs finish)
FYI - the glow plug indicator light is not an accurate gauge for glow plug time on.
Waiting until they finish, will give you a more accurate reading of the alt.
(on my 06,I can tell when the glow plugs go off at night because the lights get brighter)
That's actually very good advice from the parts guy.
( I don't wait 10-15 min.,just until the glow plugs finish)
FYI - the glow plug indicator light is not an accurate gauge for glow plug time on.
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it is worth a shot because it is about the only thing I have left. I contacted local dealership today, good folks there and they said if I have all the voltages I mentioned that about the only thing it could be is the alt. I did read an article somewhere on the net today mentioning that some of the lesser grage rebuilds have voltage regulators that are not sensative enough to pick up the start signal from the computer, But in this case I believe that is 12v,, so i am not shure that applies here.
I am gonna try it and see what happens. If I have no luck, I can get a motorcraft new alt for about 50.00 more than the reman..
I am gonna try it and see what happens. If I have no luck, I can get a motorcraft new alt for about 50.00 more than the reman..
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Truck is a 99 F250 PSD SD
Tonights mess
While running
12.2v at battery terminals
Back terminal Large red wire 12.2
Green 12.3
Orange wire started out at 8.9 but eventually got to 10.5 this was the wire that was reading 11.2 last night.
Also found a blown fuse in the break lights and backup lights are not working. This may not have any thing to do with my problem.
I tracked the orange wire on the wiring diagram to the Power distribution box and found pulled the fuse #6 checking the fuse box there is 12 volts at the box, so I am thinking the problem is in that wire between the PDB and the alternator. I will chase the wire back and test it in spots to try and find a bad spot.
Why would the voltage in that wire fluxuate?
Any assistance or suggestions would be appriciated.
I am gonna get a new plug and see if I can't at least energise the alternator to get it to charge.
Tonights mess
While running
12.2v at battery terminals
Back terminal Large red wire 12.2
Green 12.3
Orange wire started out at 8.9 but eventually got to 10.5 this was the wire that was reading 11.2 last night.
Also found a blown fuse in the break lights and backup lights are not working. This may not have any thing to do with my problem.
I tracked the orange wire on the wiring diagram to the Power distribution box and found pulled the fuse #6 checking the fuse box there is 12 volts at the box, so I am thinking the problem is in that wire between the PDB and the alternator. I will chase the wire back and test it in spots to try and find a bad spot.
Why would the voltage in that wire fluxuate?
Any assistance or suggestions would be appriciated.
I am gonna get a new plug and see if I can't at least energise the alternator to get it to charge.
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Former Vendor
Joined: Mar 2009
Posts: 8,098
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From: Westford, MA
If you guys get stuck with rebuilts that keep failing we sell brand new alternators with no core charge.
Here's a link to that section on our site.
Ford Truck Alternator
Here's a link to that section on our site.
Ford Truck Alternator
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Junior User
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That is fantastic,, if you really want to win me over and probably gain me for a customer in the future,,,then use some of that expertice to help me with this problem. I would love to buy or order an alternator in the future but TODAY my truck is sitting in the drive way costing me money I could be buying your alternator with..
Not being crappy just need to figure this out.
Thanks Jeff
Not being crappy just need to figure this out.
Thanks Jeff
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Wel there must have been issues with the second one as well because it never would charge.
I got fed up today and went to the stealership and got a reman motorcraft. That did it because now at least I have 14.2 volts so it is now finally charging however
I still have a battery light on and on occasion the voltage output spikes.
I still have that clicking noise coming out of the fuse box.
At least I can drive it,,, I just need to figure out the problem from here.
Went over all the grounds again and the battery terminals. Everything has continuity and shows little or no resistance..
I got fed up today and went to the stealership and got a reman motorcraft. That did it because now at least I have 14.2 volts so it is now finally charging however
I still have a battery light on and on occasion the voltage output spikes.
I still have that clicking noise coming out of the fuse box.
At least I can drive it,,, I just need to figure out the problem from here.
Went over all the grounds again and the battery terminals. Everything has continuity and shows little or no resistance..
Posting Guru
Joined: Mar 2007
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Are both batteries good, and do you have an isolator... It sounds like something is up or pulsing power... Maybe a hot wire vibrating on a ground?? ( engine block ect) I guess which relay is clicking will give you a head in the right direction.
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Battery light is still on, but things are better.
Unit is charginf and the starter is spinning fast when starting making me think the batteries are at least up, However that dosen't dismiss one of them being bad. I will stop in and get a load test on them today to rule them oout or verify them as a problem.
It has stopped the wild fluxuation in the guage which is a pluss but it is in the back of my mind wanting to know what is causing it. I plan to disconnect the engine ground this weekend and clean under it dielectric grease and reconnect if for no other reason than to feel better about it.
Thanks for the info thus far.
Unit is charginf and the starter is spinning fast when starting making me think the batteries are at least up, However that dosen't dismiss one of them being bad. I will stop in and get a load test on them today to rule them oout or verify them as a problem.
It has stopped the wild fluxuation in the guage which is a pluss but it is in the back of my mind wanting to know what is causing it. I plan to disconnect the engine ground this weekend and clean under it dielectric grease and reconnect if for no other reason than to feel better about it.
Thanks for the info thus far.
Posting Guru
Joined: Mar 2007
Posts: 1,191
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Ya know... You should never hook a new alternator/ regulator to a discharged battery. It plays hell on your new components... I am not sure of the batteries state, But keep in mind. If you have an alternator, with an irregular diode pattern, it will charge, not as good but still will charge, and trigger the light on the dash.
The diode gives the electricity a cyle. In america it is 60 cycles for electricla stuff. An irregular diode pattern will be maybe 50 to 70 cycles causing havoc with your systems. SOmetime the computer will even start throwing codes.
Your grounds are probably the best place to start. and battery condition.
The diode gives the electricity a cyle. In america it is 60 cycles for electricla stuff. An irregular diode pattern will be maybe 50 to 70 cycles causing havoc with your systems. SOmetime the computer will even start throwing codes.
Your grounds are probably the best place to start. and battery condition.
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