Quick history and current issue:
My 99 GT had a battery drain when I purchased the car. The previous owner was more clueless than me (bad tune, bad engine ground, did not care about battery drain) so I got a good deal on the car and quickly fixed the engine ground and found the drain (with the help of members on this forum, especially wmburns). I have not had any electrical problems since that drain other than slight rpm reduction/lights dimming when I put windows down. Fast forward to this week when I talked my wife into taking a road trip in the Mustang. I rarely use my AC so I had it on full blast on the highway. All of a sudden my battery gauge went to 0 and soon I was rolling to a stop on the highway with a bad alternator and dead battery. I started by having the battery checked and fully charged by Autozone, no problem there. I had the alternator tested at Advance Auto and it was bad so I bought a remanufactured alternator and installed it today (thanks to this forum again). When I was installing the new alt, I noticed the coolant temp sensor was toast (picture below). I thought it might not be a coincidence that the alt went and the coolant temp sensor went at the same time. After I installed all this, I took the car to have the battery and charging system tested at Advance Auto. Advance said the battery is good but the alt is at 12.4 volts without headlights on and 12.8 with headlights on. The guy there said I might need a different new alternator and that it is weird voltage went up but he had no clue why. I should have had alt checked before I installed but it was the only one there. Also, when I turned the AC on, the car slowly stalled and died (I had this issue before but my tuner fixed the issue). His idea is that my AC clutch/compressor is bad and it is causing massive drag, enough to completely kill my car. There is some good news since new alternator was installed (although with voltage where it is, I'm not sure if that's the reason). When I used to turn my lights on or roll my windows down, there would be an RPM reduction, now the RPM doesn't change at all when I have headlights on or put windows down. I have searched the forums and checked connections but was wondering if anyone has any ideas.
Thanks so much. (Pics below)
Old Ground/Tray:
New Ground/Tray:
Old Sensor:
New Sensor:
New Alt/Sensor:
My 99 GT had a battery drain when I purchased the car. The previous owner was more clueless than me (bad tune, bad engine ground, did not care about battery drain) so I got a good deal on the car and quickly fixed the engine ground and found the drain (with the help of members on this forum, especially wmburns). I have not had any electrical problems since that drain other than slight rpm reduction/lights dimming when I put windows down. Fast forward to this week when I talked my wife into taking a road trip in the Mustang. I rarely use my AC so I had it on full blast on the highway. All of a sudden my battery gauge went to 0 and soon I was rolling to a stop on the highway with a bad alternator and dead battery. I started by having the battery checked and fully charged by Autozone, no problem there. I had the alternator tested at Advance Auto and it was bad so I bought a remanufactured alternator and installed it today (thanks to this forum again). When I was installing the new alt, I noticed the coolant temp sensor was toast (picture below). I thought it might not be a coincidence that the alt went and the coolant temp sensor went at the same time. After I installed all this, I took the car to have the battery and charging system tested at Advance Auto. Advance said the battery is good but the alt is at 12.4 volts without headlights on and 12.8 with headlights on. The guy there said I might need a different new alternator and that it is weird voltage went up but he had no clue why. I should have had alt checked before I installed but it was the only one there. Also, when I turned the AC on, the car slowly stalled and died (I had this issue before but my tuner fixed the issue). His idea is that my AC clutch/compressor is bad and it is causing massive drag, enough to completely kill my car. There is some good news since new alternator was installed (although with voltage where it is, I'm not sure if that's the reason). When I used to turn my lights on or roll my windows down, there would be an RPM reduction, now the RPM doesn't change at all when I have headlights on or put windows down. I have searched the forums and checked connections but was wondering if anyone has any ideas.
Thanks so much. (Pics below)
Old Ground/Tray:
New Ground/Tray:
Old Sensor:
New Sensor:
New Alt/Sensor: