Hey there guys. I have my 04 with a refurbished alternator (put in about 2 yrs ago.) recently my battery light comes on and lights surge bright and dim along with surging ac blower. I metered the alternator output and it will go from 13.8 all the way to 15.4. My scan gauge shows that voltage while driving. The battery lint seems to come on when the voltage is high. Is my alternator shot? Trying to figure this out, thanks. Jim

 

Classic signs of a bad regulator . I would pull the Alt and replace or rebuild .

 

Okay, that's what I'll do. I'm gonna replace it. Thanks

 

Or corroded/ bad cables

Josh

 

I think you misread his issue. The output goes from 13.8 up to 15.4. Bad cables will not cause this...

 

This just happen last weekend to my son on the road. He had the alternator replaced and all is well. Also an 04. Bad new is he went to ford at the river, $507.oo to replace.
I told him to get a DC power alternator the week before. He had it checked out in Norco at the ford dealer and they told him all was well. Figure,

 

I would also have the batterys individually load tested, isolated. I know the dealer you used and they are usually pretty good.

 

The alternator receives the voltage feed on the "S" or yellow feed wire. If that particular wire has a bad or corroded connection the voltage will rise and fall.

So yes, bad or corroded cables WILL cause the symptoms.

Josh

 

I recently installed new ones, they seem real strong still

 

New alternator installed, no battery light. All is back to normal. Best part free from O'Reilly, lol. Lets see how long this one lasts. Thanks guys

 

Well, I stand corrected. I've never heard of such a thing. An alternator outputting 15.4 volts because of a corroded connection?

 

It happens. The "S" circuit is the voltage reference for the alternator. If the voltage is "low" due to corroded connection or otherwise the regulator will start cranking up the voltage on the charge wire to compensate.

The alternator isn't a one-wire connection like a POS old school GM. It uses the "S" for reference, "I" as the excite and the large cable for charge.

Josh

 

According to the Shop Manual:

The S (stator) circuit 4 (WH/BK) is used to feed back a voltage signal externally from the generator stator to the regulator. This voltage feedback signal (typically half the battery voltage) is used by the regulator to turn off the charging system warning indicator. Gas engines have an external stator circuit and diesel engines have an internal stator circuit.

A Circuit 35 (OG/LB)
The A circuit or battery sense circuit is used to sense battery voltage. This voltage is used by the regulator to determine generator output. This circuit is also used to supply current to the generator field, which determines generator output.





I could check my truck tomorrow, but is there a way to test the S (stator) circuit on a Diesel?

 

Forgot the S becomes A... my bad.

A is straight voltage, "I" is still the excite circuit.






Josh

 

I'm still confused. According to the Shop Manual for 2006, the B+ output wire is Red (RD), the I circuit is Light Green/Red (LG/RD), A circuit is Orange/Light Blue (OG/LB). This doesn't match your Yellow/White on the one you posted. Is that an older year or newer year?

In the single generator system, with the key in the ON position, voltage is applied through the charging system warning indicator I circuit to the voltage regulator. This turns the regulator on, allowing current to flow from the battery sense A circuit to the generator field coil. When the engine is started, the generator begins to generate alternating current (AC) which is internally converted to direct current (DC). This current is then supplied to the electrical system through the output terminal (B+) of the generator.


Once the generator begins generating current, a voltage signal is taken from the generator stator and fed back to the regulator through the stator circuit 4 (WH/BK). This voltage feedback signal (typically one-half of the battery voltage) is used to turn off the charging system warning indicator on the single generator system. Gas engines have an external stator circuit and diesel engines have an internal stator circuit.


With the system functioning normally, the generator output current is determined by the voltage of the A circuit. This A circuit voltage (battery sense circuit) is compared to a set voltage internal to the regulator, and the regulator controls the generator field current to maintain correct generator output.


The set voltage varies with temperature and is typically higher in cold temperatures than in warm temperatures. This allows for better battery recharge in the winter and reduces the chance of overcharging in the summer.


The single generator system consists of the generator mounted on the top right of the engine (diesel) or top center of the engine (gas). The gas engines use a 3G 115-amp generator with a 2.71:1 pulley ratio. The 6.0L diesel engine uses a 6G 110-amp (standard) generator with a 2:79 pulley ratio and a snowplow option is available for only the 6.0L diesel that includes a VR42 140-amp generator with a 2.79:1 pulley ratio.

So the lesson here is, as Bullit says, just because the 'symptoms' indicate a faulty voltage regulator, you should avoid throwing parts at it and test the system thoroughly. Don't expect the wiper boys at any of the Auto Parts stores to test it correctly for you.

Going off of the Symptoms described by the O.P., what should have occurred is:

PINPOINT TEST D: THE CHARGING SYSTEM WARNING INDICATOR IS ON WITH THE ENGINE RUNNING AND THE BATTERY INCREASES VOLTAGE



<table height="314" border="1" cellpadding="3" cellspacing="0" width="582"><tbody><tr> <th>Test Step </th> <th>Result / Action to Take </th></tr> <tr> <td> D1 CHECK THE I CIRCUIT 904 (LG/RD) FOR A SHORT TO GROUND </td> <td style="BORDER-BOTTOM: medium none">
</td></tr> <tr valign="top"> <td>

• Ignition OFF.
• Disconnect: Generator C102A (alternator electrical plug).
• Ignition ON.
• With the key in the ON position, check the charging system warning indicator.
• Is the charging system warning indicator illuminated?

</td> <td style="BORDER-TOP: medium none">Yes
REPAIR the I circuit 904 (LG/RD). TEST the system for normal operation.

No
For Diesel Engines, INSTALL a new generator/regulator assembly. REFER to Section 414-02 . TEST the system for normal operation.

</td></tr></tbody></table>