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Scottdagoalie
Scottdagoalie, Senior Master Tech.
Category: Ford
Satisfied Customers: 1940
Experience:  30 years with Ford dealers
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2006 F250: the batteries will be too dead to start truck..start engine

Customer Question

I have a 2006 F250 , sometimes the batteries will be too dead to start truck. I can tell when I am going to have this problem cause the radio & a/c will not come on right after I start engine . If you put truck in gear and drive a short ways the a/c and radio will come on. We have had the computer changed at ford because they said it had low voltage. That didn,t fix anything , only made my bilfold smaller and easier to carry. We have replaced alternator , tested batteries & cleaned terminals. I Need suggestions . Thanks Chris Beatty
Submitted: 7 years ago.
Category: Ford
Expert:  Scottdagoalie replied 7 years ago.
HiCustomer Thank you for asking your question on JustAnswer. The other Experts and I are working on your answer. By the way, it would help us to know:

-How many miles are on your Ford?
-What type of engine is in your Ford?

Thank you again for trusting us with your problem. Please reply as soon as possible so that we can finish answering your question.
Customer: replied 7 years ago.
My truck has 129000 miles and has the 6.0
Expert:  Scottdagoalie replied 7 years ago.
Does your F-250 have a single generator or dual generators?
Customer: replied 7 years ago.
single alternator
Expert:  Scottdagoalie replied 7 years ago.
To determine the problem with the charging system ,you will need to perform an alternator test .

Here are some diagrams that may help pinpoint the problem.

2006 F-Super Duty 250-550 Workshop Manual
Diesel Engines
I Circuit 904 (LG/RD)
A Circuit 35 (OG/LB)

Functionality

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.

Positive Battery Output (B+) Circuit 36 (YE/WH) (Gas Engines) / Circuit 1119 (RD) (Diesel Engines)

The generator output is supplied through the positive battery output (B+) terminal on the rear of the generator to the battery and the electrical system.

I Circuit 904 (LG/RD) Single Generator

The I (ignition) circuit is used to turn on the voltage regulator. This circuit is powered up when the key is in the ON position. Voltage is supplied from the ignition switch to the central junction box (CJB) fuse 45 (10A), then to the instrument cluster and through the charging system warning indicator (battery icon) to the generator. This circuit is also used to turn the charging system warning indicator on if there is a fault in the charging system operation.

S Circuit 4 (WH/BK) (Gas Engines)

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.

2006 F-Super Duty 250-550 Workshop Manual
PINPOINT TEST A: THE BATTERY IS DISCHARGED OR BATTERY VOLTAGE IS LOW
Test Step Result / Action to Take
A1 CHECK THE BATTERY CONDITION
  • Carry out the Battery — Condition Test to determine if the battery can hold a charge and is OK for use. Refer to Section 414-01.
  • Does the battery pass the condition test?
Yes
GO to A2.

No
INSTALL a new battery. REFER to Section 414-01. TEST the system for normal operation.
A2 CHECK THE GENERATOR OUTPUT
  • Carry out the Generator On-Vehicle Load Test and No Load Test. Refer to the Component Tests in this section.
  • Does the generator pass the component tests?
Yes
GO to A3.

No
INSTALL a new generator. REFER to Section 414-02. TEST the system for normal operation.
A3 CHECK FOR CURRENT DRAINS
  • Carry out the Battery — Drain Testing. Refer to the Component Tests in this section.
  • Are any circuits causing excessive current drains?
Yes
REPAIR as necessary. TEST the system for normal operation.

No
GO to A4.
A4 CHECK THE VEHICLE GROUNDS
  • Start the engine.
  • With the engine running, measure the voltage drop between the generator housing and the negative battery terminal.
    graphic
  • Is the voltage drop less than 0.1 volt?
Yes
GO to A5.

No
CHECK the engine ground, generator ground and the battery ground for corrosion. TEST the system for normal operation.
A5 CHECK THE VOLTAGE DROP IN THE B+ CIRCUIT 36 (YE/WH) (GAS ENGINES) / CIRCUIT 1119 (RD) (DIESEL ENGINES)
  • With the engine running, measure the voltage drop between the generator B+ C102C, circuit 36 (YE/WH) (gas engines) / circuit 1119 (RD) (diesel engines) and the positive battery terminal.
    graphic
  • Is the voltage drop less than 0.1 volt?
Yes
CHECK if the customer left any electrical system(s) on or if there is an intermittent excessive battery draw. TEST the system for normal operation.

No
CHECK for any corrosion in the B+ circuit 36 (YE/WH) (gas engines) / circuit 1119 (RD) (diesel engines), positive battery cable and/or connections. REPAIR as necessary. TEST the system for normal operation.
Customer: replied 7 years ago.
we have already had all of these checked . the problem i am having is a ford problem not an alternator problem. I have seen alot of other people on internet with same problem but no answers. I am hoping to talk to a ford tech that has dealt with this problem and knows what is causing it.
Expert:  Scottdagoalie replied 7 years ago.
Did you replace the alternator with a ford unit or aftermarket?We have seen several aftermarket/rebuilt alternators fail within a short time.
Customer: replied 7 years ago.
no your answer didn,t help me. I was looking for a tecnition who has had this problem come into a dealership. This seems to be a fairly common ford problem. I am seekeng someone who knows exactly what my problem is not someone to tell me how to diagnose an alternator.

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