How do I test or trouble shoot an 89 Ford Mustang 4cyl. that just lost all electrical power while going down the road at speed. It seems the pos. bat cable shorted out against the ignition post on the soelenoid, the soelenoid looked like toast so it was replaced but we still cannot get the starter to work. we might have hooked the wires up backwards could that ruin the new soelenoid?

 

Check all your main fuses, too.

Hooking the wires up backward shouldn't ruin the solenoid, but could cause things to act wierd or not work at all.

 

just switch the wires out after you check for blown fuses andfor future reference, try putting some electrical tape on the solenoid to prevent any future shorts.

 

If I remember correctly, you should have the cable from the battery that goes to one of the solenoid terminals. Also attached to this terminal are one or two other wires that feed the rest of the car. It should not make any difference which terminal you use because they only get connected to the starter when that solenoid is energized. The other large solenoid terminal gets connected to the starter only. (only one cable)
The wire from the ignition switch is the one that energizes the solenoid. The two wires that are feeding the electrical system of the car may have fusible links in them. Just tug on them and if they feel stretchy the links are open. They are there to protect the electrical system in case of any very heavy current drain(short). If the solenoid has only one small wire from the ignition switch then the ground for the solenoid to operate is made through the sheet metal of the fender. If there is some rust and corrosion it would be a good idea to run a separate ground wire from one of the solenoid mounting bolts to the engine or the battery negative terminal.
If the positive cable short circuited to the ignition post of the solenoid the starter would have engaged and tried to start the car. I believe you either have a real short circuit somewhere else in the wiring or a heavy current drain somewhere in the system and that caused the solenoid to overheat. Also poor connections will cause heat to develop and melt wiring.. Did you have trouble getting it started at any time and had the solenoid engaged for a longer period of time than normal? If you connect the wires as suggested and everything works , you are done. Just make sure you keep the connections clean and tight.

 

I had the same problem too, and this solved it. Thank you gbear!