Question about 1994 Ford Thunderbird

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Voltage drop I have a 1994 thunderbird and have replaced the battery 2 times and the altenater twice. The troubles I'm having is when the RMPs get to 2000 the voltage on drop to 0 if I hold the throtle at that rmp. After charging the battery so it will start and letting it idle which it will do just fine so the alternate can charge the battery it wont take but 15 20 minutes later I will go out to start it again and it will be completely dead again. I have replace the ground and positive cables to starter and every where. Two notes I want to make is that when it was driveable the problem would only accure in between 2000 and 3000 RPM then it would run normal after 300 RPM. Also it started after I replaced the oil presure sending senser. Thanks for any help.

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  • sparky_3 May 30, 2009

    Its a 4.6L

  • sparky_3 May 31, 2009

    It is internal

  • gerry bissi May 11, 2010

    Integral Generator/Regulator
    When the engine is started:

    • The generator (GEN) (10346) begins to generate alternating (AC) current which is converted to direct (DC) current by the rectifier (10304) assembly internal to the generator.
    • The current is then supplied to the vehicles' electrical system through the output stud located on the rear of the generator.

    With the system functioning normally:

    • The generator output current is determined by the voltage at the 'A' circuit (battery sense voltage).
    • The 'A' circuit voltage is compared to a set voltage internal to the generator regulator (10316) , and the generator regulator controls the generator field current to maintain proper generator output.
    • The set voltage will vary with temperature and is typically higher in the winter than in the summer allowing for better battery charging.

  • Greg Margossian
    Greg Margossian May 11, 2010

    It was screaming regulator until I found out it was internal and you replaced alternator twice. Would only be guessing but only a few other places to look. Apart from the solenoid pulling too much power, the only other place I would investigate b/4 having an electrical specialist look at it is the Daytime Running Lamps which would make sense since they are on all the time. Still looking for you but quite honestly, don't have a solution yet.

  • Colin Stickland
    Colin Stickland May 11, 2010

    is it an older vehicle with a seperate voltage regulator

  • Greg Margossian
    Greg Margossian May 11, 2010

    Is voltage regulator internal or external?



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Had some help here ,everything is pointing to the altenator .Sorry to say after you have changed it twice but i think you have been unlucky and replaced the unit with one with the same fault ---was it a new one or scrapyard ?? start engine and then hold rpm at 1500/2000rpm and disconnect battery if engine continues to run then altenator is charging ,now turn everything electrical on and see if engine continues to run ,if it does then altenator is ok ¿¿¿¿sort of ??.Right now stop engine .Leave overnight and see if it starts (battery disconnected) if engine starts ok then it could be one of two faults,firstly a diode is faulty in the altenator ??or a DISCHARGE like a boot light on ??big amp in the boot for music left on? anything stupid in fact .Quick one here is if after following my advice then not sure ,disconnect altenator and leave battery connected ,if it then goes flat then it something on in the car with a drain of more than 21watts .Divide volts into watts gives you the amperage being drawn.If it starts then its the diode pack in the altenator.Best of british with it .

Posted on Jun 02, 2009


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