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Old 01-16-2006, 06:48 PM
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alternator problems

the alt. on my truck charges when it wants to.. it is a brand new 100 amp ford alternator.. it wont charge at idle even though the crank pulley is 6" and the alternator pulley is 2 " i don't know the ratio but if the engine is turning 6 to 700 rpm the alternator should be turning somewhere around 1800 or less (best guess) well above the cut on rpm that the paper work came with it said (900 rpm) what could be causing the alternator to act like this ....the pan gasket leaks in the front do you think that if oil got slung in the alternator that would make it erratic? or could the brush springs gotten hot weaken or the voltage regulator has gone bad? when i turn on the heater fan the head lights it drops down to 11 volts. and if you blow the horns it drops down to 10 volts .. let it run like that to long and the truck loses power due to the fact that the coil is not firing hot enough(it is a performance coil) with the fan and lights that cant be over maybe 40 amps or 50 tops i am guessing.. how do i check each device to see if there working correctly (charging circuit) the specs said that the constant amp draw on the alternator was 85 amp i have 3 10 gauge wires going from the alternator to the battery and 2 10 gauge wires feeding the truck and one 14 gauge wire grounding the battery to the chassis and a 1 ought ground wire and a number 2 positive wire about 12 " long and a brand new battery what else can i do

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Old 01-17-2006, 12:45 AM
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Doc here,

Sounds to me like you got an OBF..(Out of Box Failure) Not surprising since about 1 of 3 are bad now adays...

To test it, just put a DVOM across the Battery Cables set for V X 50 or autorange, Take a reading, the Battery should be about 11.95 to 12.2 volts static, If not (like 10 or lower, you have a dead cell, replace the battery)

NEXT run it, and let it idle..It should read 14.4 optimum, 13.96 is acceptable. If your getting lower than that, think warrenty....

OR you could go back to where you purchased the Alternator and instruct them to do a load/charge test on it..usually for free..

If under RPM load it suddenly "Slams in" you have a bad regulator..(I don't remember and am not a Ford guy at all, but I think all those are Externally Electronic Regulators.

You Could have, If all else test out good, Bad Grounds, Set up a ground system this way:

Run a properly gauged Ground cable from the battery to any handy bolt at or near the starter, From that same bolt get a Battery cable at the parts store, that has two 3/8 ring terminals on each end and attach it there and to the Frame.

Next get some 10 gauge wire and ring terminals and run that from your bolt on the block to the Firewall, and another to the Alternator bracket or mount bolt.

Next get some Wire Braid, (Radio Shack) and install braid from the radiator support to the frame, Fenderwells to frame , hood to firewall, Doors to door posts, gas flap to body, tailgate / Trunk to body.

At each point the wire is grounded, Burnish ALL the paint and grease off to bare metal. Use a proper star-washer and lock. Use sheetmetal or Tech screws where no screws are available.

It sounds like a lot of work, but after you assemble all the parts, it's only a few hours to do..and you'll end up with a system that will work reliably for many years to come..and can eliminate that from your troubleshooting list.

Let us know what you find!

Doc
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Old 01-17-2006, 07:29 AM
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Doc has seemed to cover it all but the thing that caught my eye is the oil leak,most com,on fords if it the water pump starts leaking it will have the same results,so i think you should try a new belt,and try to keep the oil off it,and see if it does any better,if knot i would try what doc said,
My,$0.02
Donald Stabnau
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Old 01-17-2006, 01:55 PM
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alternator whoes

thanks for all the help i found out what he problem was it was a faulty reg and the fuse panel had some corrosion on some of the terminals after i cleaned all of this it went to working at idle but i did find one more problem the main power wire feeding the fuse panel is only 10 gauge for just about everything in the truck i am going to double it up so that it will have more capacity ......but i am still going to add the extrat grounds and clean with a wire brush the factory ones




I do have a question does anybody know where i can download the wiring diagram for my truck or atleast one close to it
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Old 01-17-2006, 04:53 PM
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Quote:
Originally Posted by woodmanscott@hotmail
I do have a question does anybody know where i can download the wiring diagram for my truck or atleast one close to it

Doc here,

What Truck are we talking about here?

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Old 01-17-2006, 07:14 PM
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wiring diagram

oppps i am sorry i forgot to say what kind of truck it was .....It is a 84 F 250 with a 351 windsor 4x4 automatic tranny
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Old 01-18-2006, 05:59 AM
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Doc here,

Here ya go...




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Old 01-18-2006, 06:06 AM
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wiring diagram

thanks doc it should help... it is alittle blurry could you send it strait to my email
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