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old ford regulator alternator question

9K views 5 replies 5 participants last post by  JeffB 
#1 ·
My 73 cougar suddenly started running down batteries. I bought a new battery and after charging to top it off and load testing it I'm satisfied that its good for testing the alt.

351C 2V engine, with 1G 3-wire alt 65AMPs, Externally mounted points-type regulator.

Engine off: battery 12.6v
Engine ON, excited, no load: Battery 12.3v
Engine ON Back BAT terminal tests: 12.2v

Is the ALTERNATOR bad for sure, or can I be getting a low reading off of the BAT terminal because the REGULATOR is bad?
 
#4 ·
would you like to test first...


you will want to print this test and perform it..

http://i.imgur.com/WMDprhm.jpg

test 5 is to the threaded stud on the battery side of the starter relay on fords..

the six steps of the voltage drop test is important to do first.. you may have a different issue that is causing you problems.

there are two slightly different charging system set ups..

one that uses a indicator light with a wire on the I terminal and one without..

usually i have a 3 inch 14 gauge jumper wire with male 1/4" quick connects..

i have the engine running.. the voltage regulator is unplugged. the digital volt meter is set to 20 volts DC.. the test leads are hooked to the positive and negative battery cables..

jump the removed connector for the voltage regulator wiring.. from the F terminal to the A terminal.. the voltage on the battery should increase.. you will have to bring the RPMS up slightly while watching the voltage.. you need to be really quick with this test.. you don't want to overheat the rotor winding. if you can get the output voltage over 15 volts the diodes are probably OK..

pull the jumper off the regulator pigtail..

change the volt meter to AC volts.. leave the test lead hooked to the negative battery.. move the positive lead to the S terminal in the regulator pigtail.. plug the jumper back in from F to A.. you should now have about half the output voltage... so if you are getting 14 volts.. you should see about 7 volts AC on the stator wire.. if you get more than half of the charging voltage.. you have bad diodes..

the F terminal hooks to the back of the alternator.. inside to one of the two brushes. the other brush is grounded.. the regulator sends positive and negative pulses down the Field wire.. positive pulses to increase the size of the rotors magnetic field to increase alternator output.. to moderate the output. the voltage regulator will ground the field wire.. the voltage regulator is actually vibrating the contacts.. using the Stator AC voltage to create the frequency to do the vibrating and keep it proportional to the speed of the alternator.

the S terminal is the stator connection.. it will have half the charging voltage only when the alternator is actually putting out voltage.. all three stator windings are connected directly to this STA ..

The A terminal on the regulator. on systems that use 4 wires to the regulator.. it will have constant battery power from the starter relay.. on cars that use AMP meters that have 3 wires only ..it will usually be Switched by the ignition switch

the I terminals on the regulator. this is only used on cars with alternator lights..

one side of the alternator light is hooked to the I terminal.. the other side of the alternator light is hooked to the ignition switch wire that feeds into the dash cluster..

when the key is turned on.. the gauges get power as does the light. the I terminal at the regulator will be LOW in voltage as the charging system is not working..

when the alternator charging voltage comes up. the regulator I terminal and the power to from the ignition switch is about the same.. so it will have 14 volts on either side of the bulb and it will go dark.. if the charging system does not work.. the light will be on.. if it glows.. you could have resistance in the system.

sorry for the wall of text.
 

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#5 ·
Resolved: I spent the morning taking the fender-mount solenoid and regulator connectors of and giving each a cleaning. I was hoping that the problem might be in the ground from the battery to the fender or from the alt to the fender or regulator... I bought a new electronic regulator but it was in my truck, which my wife took to work while I scared the ghosts away from her car.

She pulls up and since I had the regulator and solenoid off, I just replaced it- I was out doors in the light rain, if that gets me off the hook. Anyways, fired it up and from 12.4V OFF to 14.6 at slow idle it looks like the problem was resolved. I'm thinking the ground, because wires were fairly dirty in the connectors. But it may have been the regulator :thumbup:

Thanks for all the help, and have a great Thanksgiving!
 
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