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Post by 88turbobird on Jul 18, 2018 12:50:45 GMT -5
So I was driving my 88 TC last weekend and noticed that it was running a little rough. I drove to my parent's house, shut off the car and went to immediately start it again and got the "slow crank, battery is dead". I attached my battery charger and the car did turn over and start but once I removed the charger the voltage started to drop immediately. I'm running a PimpX ECU so I was watching the voltage gauge on the laptop. My immediate thought was the alternator is not charging the system. I'm running a PA Performance 3G alternator and have it wired as outlined in the NATO tech guide. I removed the alternator and had it tested at Autozone. They said it failed all tests so I shipped it to PA Performance. PA Peformance reached out today and said the alternator is passing all of their tests just fine (taking their word over autozone) so my question is what could the problem be? The battery is two years old so I don't think that would be the problem but could it? I haven't checked it yet. PA Performance also sent me a diagnostic sheet that suggests comparing the voltage at the battery versus alternator output post and checking the voltage readings of the individual wires on the 3 wire regulator plug. Any other ideas out there? Thanks everyone
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Post by Stinger on Jul 18, 2018 13:49:37 GMT -5
If it's the battery then it will lose charge without the engine running. When running, if the alternator and wiring is all working then it can run off the alternator power even if the battery is junk.
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Post by 88turbobird on Jul 18, 2018 14:41:28 GMT -5
If it's the battery then it will lose charge without the engine running. When running, if the alternator and wiring is all working then it can run off the alternator power even if the battery is junk.
Well the car would run once jumped but the voltage would drop as soon as I removed the charger. The car was also running like crap; I'm guessing because the ignition system was not getting enough juice. I'm going to check the battery later today and report back
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Post by Stinger on Jul 18, 2018 16:00:23 GMT -5
You can check alternator output when it's running by simply checking voltage at the large wire output on the alternator. It should be 14-14.5v or so (about 2v above battery voltage). If this isn't the case, the alternator isn't charging the battery.
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Post by 88turbobird on Jul 19, 2018 8:22:22 GMT -5
You can check alternator output when it's running by simply checking voltage at the large wire output on the alternator. It should be 14-14.5v or so (about 2v above battery voltage). If this isn't the case, the alternator isn't charging the battery. I went through the diagnostic checklist that PA Performance sent me. Battery registered at 12.3V, alternator output post registered at 12-12.1V, and for the 3 wire regulator plug I had the following: Green wire with red stripe (ignition switch): 11.8V; good White Wire (stator wire): Full continuity (voltage regulator to grey clip); good Yellow wire (sense wire): No Voltage at Plug!! (PROBLEM)
The sense wire should receive battery voltage at all times. If this wire does not have voltage, the alternator will not charge. After some looking around, I found my original connection to the harness wire to be separated. After fixing the connection, I was once again receiving battery voltage at the plug. This seems to be my problem. I will confirm once I receive the alternator back from PA performance but I wanted to provide this for anyone who runs into a similar situation and needs to troubleshoot a battery versus alternator issue.
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Post by Stinger on Jul 19, 2018 10:35:44 GMT -5
Good to hear you found the problem.
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