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Bob, Auto Service Technician
Category: Car
Satisfied Customers: 4087
Experience:  40 year GM Tech. +30 Certified. ASE Master Tech.(expired, retired) Medium Duty, Heavy Line, Retired
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what happens when you cross jumper-cables the wrong way

Customer Question

i did this and now nothing works. it makes no sound when you try to start it and the lights won't even turn on. i replaced the battery but that wasn't it.
Submitted: 9 years ago.
Category: Car
Expert:  Bob replied 9 years ago.
Many times when a battery is connected backward or jumpers are mis installed it will blow the diodes out of the alternator, but if it won't run it can't be tested for that problem. More of a chance that the fusible links have been burnt up. Fusible links are wires that are smaller than the other wires in the circuit that they are connected to and they are designed to blow out in the event of a major electrical problem to protect the rest of the system. They are a smaller wire and normally a different color than the other wires. On most Fords, they can be found connected to the back of the alternator, the battery, the starter solenoid and sometimes in the main wiring harness. When you locate them you can usually just pull on the insulation around the wire and if you can feel the insulation stretch, that is a pretty good indication that the wire on the inside is burnt out as it is supposed to do to protect the system, similar to a fuse, but made of regular wire instead. The other thing you could do, is to use a 12 volt test lamp or a volt meter to see where you have voltage and where you do not. But it sounds like you have lost a main positive connection that feeds the whole system and I would be checking around all of the major components, like the alternator, starter and solenoid for burnt out links. If you need more help, just drop me a note.Thanks

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