Gary Lewis Posted November 20, 2017 Share Posted November 20, 2017 You still didn't pull the alternator wire and let it sit over night to see if it was dead yet? right? That's a good point, Pete. If the alternator is bad and you do my test the light will still be on when all the fuses are pulled. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted November 20, 2017 Share Posted November 20, 2017 I taken the battery completely out, charged it up over the weekend, I'm taking the battery and the alternator down to the parts house and have them tested again. want to make sure I did not damage the battery with the overcharging from the bad regulator. If you don't have a meter, you have to have them test for backflow not just output. Even the free Harbor Freight meters have diode test. It looks like a line with a box and arrow in the middle. Link to comment Share on other sites More sharing options...
jdavidsmi Posted November 20, 2017 Author Share Posted November 20, 2017 If you don't have a meter, you have to have them test for backflow not just output. Even the free Harbor Freight meters have diode test. It looks like a line with a box and arrow in the middle. Did not get into town today, so I put the battery back in and disconnected the alternator. the voltage across the battery this evening was 12.73 I will check tomorrow and see what happen. David Link to comment Share on other sites More sharing options...
Gary Lewis Posted November 20, 2017 Share Posted November 20, 2017 Did not get into town today, so I put the battery back in and disconnected the alternator. the voltage across the battery this evening was 12.73 I will check tomorrow and see what happen. David I think you've found the problem. Better have the alternator tested. Again. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted November 20, 2017 Share Posted November 20, 2017 Did not get into town today, so I put the battery back in and disconnected the alternator. the voltage across the battery this evening was 12.73 I will check tomorrow and see what happen. David 12.73V is high for a battery at rest. I'm used to seeing 12.56 or so. If you do have a meter or self powered test light, simply test from the alternator lead to ground. Some DMM's will not pass enough current in 'ohms' to get the diodes to block, but a test light or diode function will show that they are bad. Or just hook the battery back up and wait a half hour, and feel the alternator case. Is it warrm? Yeah the diode(s) are bad. Link to comment Share on other sites More sharing options...
PetesPonies Posted November 21, 2017 Share Posted November 21, 2017 12.73V is high for a battery at rest. I'm used to seeing 12.56 or so. If you do have a meter or self powered test light, simply test from the alternator lead to ground. Some DMM's will not pass enough current in 'ohms' to get the diodes to block, but a test light or diode function will show that they are bad. Or just hook the battery back up and wait a half hour, and feel the alternator case. Is it warrm? Yeah the diode(s) are bad. Not if just turned off it isn't. 2.1V is the textbook spec for a cell, thus 12.6V. But the charging is greater, so when you first turn the engine off, the battery will read higher. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted November 21, 2017 Share Posted November 21, 2017 Not if just turned off it isn't. 2.1V is the textbook spec for a cell, thus 12.6V. But the charging is greater, so when you first turn the engine off, the battery will read higher. Right. Like I said 12.7x is high if the surface charge is gone. So, that reading must have been fresh off the charger. No battery is 'perfect' and I usually see something a little below the ideal for a LA battery. Regardless, there are any number of ways to figure out if the diodes are bad. Try figuring out if the 2G "fire plug" has gone south. Link to comment Share on other sites More sharing options...
FuzzFace2 Posted November 23, 2017 Share Posted November 23, 2017 Right. Like I said 12.7x is high if the surface charge is gone. So, that reading must have been fresh off the charger. No battery is 'perfect' and I usually see something a little below the ideal for a LA battery. Regardless, there are any number of ways to figure out if the diodes are bad. Try figuring out if the 2G "fire plug" has gone south. I thought that was an easy one to figure out no? https://cimg5.ibsrv.net/gimg/www.ford-trucks.com-vbulletin/2000x1198/80-20171104_171815_3ea9a2879b6917c7e3901d278453fe6aa298c79c.jpg Dave ---- Link to comment Share on other sites More sharing options...
Gary Lewis Posted November 23, 2017 Share Posted November 23, 2017 Right. Like I said 12.7x is high if the surface charge is gone. So, that reading must have been fresh off the charger. No battery is 'perfect' and I usually see something a little below the ideal for a LA battery. Regardless, there are any number of ways to figure out if the diodes are bad. Try figuring out if the 2G "fire plug" has gone south. I thought that was an easy one to figure out no? https://cimg5.ibsrv.net/gimg/www.ford-trucks.com-vbulletin/2000x1198/80-20171104_171815_3ea9a2879b6917c7e3901d278453fe6aa298c79c.jpg Dave ---- I think there’s a lot more wrong than just the connector in that picture. 🙈 Link to comment Share on other sites More sharing options...
85lebaront2 Posted November 23, 2017 Share Posted November 23, 2017 Right. Like I said 12.7x is high if the surface charge is gone. So, that reading must have been fresh off the charger. No battery is 'perfect' and I usually see something a little below the ideal for a LA battery. Regardless, there are any number of ways to figure out if the diodes are bad. Try figuring out if the 2G "fire plug" has gone south. I thought that was an easy one to figure out no? https://cimg5.ibsrv.net/gimg/www.ford-trucks.com-vbulletin/2000x1198/80-20171104_171815_3ea9a2879b6917c7e3901d278453fe6aa298c79c.jpg Dave ---- Actually on the up to 1987 2G system, the voltage sense for the POS is beyond the fusible links, look at the 1986 EVTM on the website. If it fails, or has a bad connection if the alternator has been replaced with one that has the "fire plug" permanently attached, the alternator will not charge and will promptly destroy itself. Matt blew one on his 86 F150 due to that, fortunately I still had a good one from Darth and was able to help him. I still say, I want whatever it was the engineers at Ford were on when that was designed, it must have been some "dynomite sheet mon". Link to comment Share on other sites More sharing options...
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