Rindelmach1 14 Report post Posted November 21, 2018 need help with connecting a new 69 mach 1 alternator wiring harness. i bought the one with tach since i have a tach car however my old plug has 4 prong plug but one is blank. can someone send a pic of the connections on both ends? https://www.cjponyparts.com/WALT5B/p/WALT5B/?utm_source=Pony&utm_medium=Email&utm_campaign=OrderConfirmation&lac_guid=dc8f286e-8eb0-e811-80fa-0050568938fc Quote Share this post Link to post Share on other sites
Brian Conway 264 Report post Posted November 22, 2018 Stock 69 CJ w/tach and 55 amp alt. The 4 wire voltage regulator connection is a spade type connector. Brian Quote Share this post Link to post Share on other sites
Rindelmach1 14 Report post Posted November 22, 2018 the old cable i have has the 4th black/red wire cut off but it works. the new cable has the black/red wire. if i trace it all the way out it goes to chassis ground. not sure why i get an alternator light after starting it. Quote Share this post Link to post Share on other sites
Brian Conway 264 Report post Posted November 22, 2018 Why the Black w Red is cut is a mystery left by the last owner ? I guess your going to have figure it out ? I think I would hook everything up, plug it all together, check the battery readings for awhile and see what's up ? Brian Quote Share this post Link to post Share on other sites
Rindelmach1 14 Report post Posted November 23, 2018 Issue is the alternator dummy light goes on with new cable. Strangely enough, i put back the old cable and now i still have the alternator dummy light. with car off my battery reads 13.4v. After its started, it reads 14.5v which means its getting regulated which is good. If i remove the negative of the battery while car is running, she still runs. So i think the alternator is good but something weird with the dummy light being grounded. Do you know how the dummy light works and which wire color controls it? Quote Share this post Link to post Share on other sites
Brian Conway 264 Report post Posted November 23, 2018 Your battery readings seem to be pretty high and may be a clue ? My battery readings are, engine off, 12.53 -12.75. Engine idling at 800 rpm readings are 14.10 -14.19. Chart is from the 69 Wiring diagram booklet. Brian Quote Share this post Link to post Share on other sites
Rindelmach1 14 Report post Posted November 23, 2018 Whats puzzling me is why the alternator light is on even with my trusted old harness. I unplugged the connector to regulator and tested 12v on plug that would connect to regulator I (other end grounded). I also tested 12v on A but 0 volts on S and F. I tried switching my voltmeter to AC when checking S off alternator which i assumed is sator and AC voltage. Looking at the wiring diagrams you can see the sator is pre diode. Very strange. Could you send me the left side of the diagram which shows the complete regulator and alternator? Quote Share this post Link to post Share on other sites
1969_Mach1 333 Report post Posted November 23, 2018 Rindelmach1, Do you have a copy of the factory Ford service manuals? They are reprinted and inexpensive. If so, look on page 14-01-02 of Volume 3, Electrical, figure 1. There is a simplified electrical schematic showing everything in the charging system including internal regulator and alternator components. From looking at mine, your problem can easily be the regulator or no voltage output from the stator terminal on the alternator. Stator output voltage on the alternator is roughly half of the charging voltage. The stator voltage goes to the "S" terminal on the regulator. This in turn operates a relay inside the regulator to turn off the light. My manuals are hard copy. I'll try to take a picture of the diagram and upload it. Quote Share this post Link to post Share on other sites
Brian Conway 264 Report post Posted November 23, 2018 The Only other schematic does not show any other details. OK so I 'll say it another way. A battery reading of 13.4 is way to high and my even be dangerous. I would try switching batteries and if the warning light persists I would change out the voltage regulator. Brian Quote Share this post Link to post Share on other sites
1969_Mach1 333 Report post Posted November 23, 2018 A freshly charged battery will often have more than 13V. For the last 15 years when my Mach 1 is parked I've disconnected the battery and have kept a Battery Tender on my Optima Red Top battery. I just disconnected the Battery Tender and measured the battery voltage, it was 13.47V. What shuts off the light is equal voltage on both sides of the bulb to stop current flow through the filament. I'm thinking it should shut off with the battery voltage he has. Battery voltage, 2.1V per cell, 6 cells equals 12.6V. You usually see 12.6V plus or minus a couple of tenths on a battery that has been sitting for a while. Quote Share this post Link to post Share on other sites
Rindelmach1 14 Report post Posted November 27, 2018 Should I see voltage at the stator? If the system is regulating then I assume its producing AC but I didn't see any with voltmeter Quote Share this post Link to post Share on other sites
Rindelmach1 14 Report post Posted December 1, 2018 this may be a dumb question but how i can check the Stator for voltage? getting nothing when connecting stator on back of alternator to VM and ground. Quote Share this post Link to post Share on other sites
