Denver T-Bird Posted October 14, 2018 Share Posted October 14, 2018 I finally got to have some fun driving my Tbird around town. I stopped to get some gas and then could not start the car and had to get a jump. Once I got home I connected a volt meter to the battery and jump started the car again. Driving around town the volt meter would read 11.8 volt for a while (even at RPM 2000) then jump to 13.8 volts. I drove the car for about 20 minutes, during the drive the voltage dropped slowly from 13.8 to 12.8 volts and held steady. I was able to start the car with out a jump later in the day. I am assuming that the brushes on the generator some how are intermittent? Why would the voltage drop to 12.8 volts? (is this because the battery was charging) I have a new voltage regulator. I am assuming that the generator needs to be rebuilt ?? Is there anything else to check? The battery is about 1 year old and reads and 12 volts after sitting for a day. Thanks Link to comment Share on other sites More sharing options...
TerryB Posted October 14, 2018 Share Posted October 14, 2018 Loose fan belt? Good,clean connections from generator to volt regulator. Loose or dirty batter cable, esp ground cable. And of course brushes not making good contact. Link to comment Share on other sites More sharing options...
TerryB Posted October 14, 2018 Share Posted October 14, 2018 Is your regulator the points contact kind? The points might have been a bit dirty or sticking. Link to comment Share on other sites More sharing options...
stvaughn Posted October 15, 2018 Share Posted October 15, 2018 At 12 volts your battery is not fully charged and 20 minutes driving is not nearly enough to charge it. Read this. http://cdn2.hubspot.net/hubfs/2154717/pdf/faq.pdf Link to comment Share on other sites More sharing options...
Denver T-Bird Posted October 16, 2018 Author Share Posted October 16, 2018 Hi TerryB, Belt is tight, cleaned contacts and wires for generator / voltage regulator awhile back. The regulator is new and is the points kind. Battery cables are tight. Suspect the brushes in the generator are sticky/worn. Thanks for the suggestions. 1 Link to comment Share on other sites More sharing options...
TerryB Posted December 22, 2018 Share Posted December 22, 2018 Do you know what the resistor value should be? Did the generator test ok? Regulator grounds are critical for correct operation so I would look there to start. Link to comment Share on other sites More sharing options...
Denver T-Bird Posted December 23, 2018 Author Share Posted December 23, 2018 The generator did test OK. I realized that when the contacts are closed the resistor looks shorted. When I press on the contact to open them the resistance is about 35 ohms across the Arm and Field resistor. A new regulator shows 35 ohms without having to press the contacts open. I did clean the ground and all terminal leads with some sandpaper to ensure they have good clean contact. Link to comment Share on other sites More sharing options...
Dave39MD Posted December 23, 2018 Share Posted December 23, 2018 (edited) Does your manual spell out how to polarize the generator and has it been done? Maybe you don't have to on a ford system. Dave Edited December 23, 2018 by Dave39MD (see edit history) Link to comment Share on other sites More sharing options...
TerryB Posted December 23, 2018 Share Posted December 23, 2018 (edited) Some generator trouble areas to inspect are shown on this phamphlet that came with a rebuilt generator. Note the G terminal on the regulator is also the A or armature terminal on other drawings of the regulator circuit. Edited December 24, 2018 by TerryB (see edit history) Link to comment Share on other sites More sharing options...
Frank DuVal Posted December 24, 2018 Share Posted December 24, 2018 14 hours ago, Dave39MD said: Maybe you don't have to on a ford system. All generators need to have some residual magnetism to self start charging. Polarizing magnetizes the field coil pole pieces so the generator will start charging. Brand does not matter, except in the method of polarizing. Link to comment Share on other sites More sharing options...
Bloo Posted December 24, 2018 Share Posted December 24, 2018 On 12/22/2018 at 5:43 PM, Denver T-Bird said: When I press on the contact to open them the resistance is about 35 ohms across the Arm and Field resistor. That sounds reasonable. On 12/22/2018 at 5:43 PM, Denver T-Bird said: A new regulator shows 35 ohms without having to press the contacts open. And that sounds wrong. I have no ford books handy, but IIRC 12v to the field terminal makes it charge, so whenever it is trying to charge, the field terminal would be shorted to the armature terminal by points in the regulator. When either the voltage or current gets too high, a relay would pull down (there's 2 relays, one for voltage and one for current), and remove the short. Once the short is removed (points open). the resistor you are seeing (between the armature and field terminals), and another resistor to ground form a voltage divider for the field terminal, sending the field something much less than the 12+ volts it was getting when the points were closed. This makes the generator barely charge. In operation, the voltage regulator relay probably vibrates very quickly between "hard charge" mode and "barely charging" mode as soon as the battery is getting close to fully charged. Link to comment Share on other sites More sharing options...
Denver T-Bird Posted January 9, 2019 Author Share Posted January 9, 2019 Thanks to all for the suggestions. I removed the generator and took 4 voltage regulators (1 original, 1 purchased in May and was tested and found bad and 2 units recently purchased online) to a new shop. The generator tested good, again. The 2 new regulators purchased online were verified bad. The shop even removed the cover and made adjustments but could not get them to work. The one I purchased in May was tested and found to be working fine. Surprised to find that new units were bad from the start and the one the first shop thought was bad, is working. Now all is charging as it should. Thanks again! 3 Link to comment Share on other sites More sharing options...
Friartuck Posted January 9, 2019 Share Posted January 9, 2019 Thanks for following up on this thread. We all can learn from other collector's experiences. 1 Link to comment Share on other sites More sharing options...
TerryB Posted January 9, 2019 Share Posted January 9, 2019 Sadly even new parts can’t be trusted to work. Your follow up post will help others who may be having similar issues. Glad to hear it’s fixed. 1 Link to comment Share on other sites More sharing options...
Frank DuVal Posted January 10, 2019 Share Posted January 10, 2019 Curious if the new regulators purchased online were recent manufacture or NOS from years ago. Link to comment Share on other sites More sharing options...
Denver T-Bird Posted January 11, 2019 Author Share Posted January 11, 2019 The regulators were Standard Motor Products VR35. Link to comment Share on other sites More sharing options...
Roger Zimmermann Posted January 13, 2019 Share Posted January 13, 2019 This is no surprise for me. I bought several regulators in the US; they all were bad and not charging. The one I bought locally was sure more expensive, but it was functioning properly. Link to comment Share on other sites More sharing options...
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