Go Easy on Me



I made a huge mistake the othe rmorning while late for work and jumpstarting my car. You may have guessed it…I hooked the jumper cables up backwards. I know VERY STUPID and Irresponsible…I had the battery, alternator and negative cable replaced. BUT the headlights and interior lights only work while engine is running. The radio doesn’t work anymore, and the brake light and batt light stay lit on the dash panel.

Go easy on me, is it worth the $$$ it might cost to have this fixed? Can it be fixed? what should I do?


I would inspect all of the fusible links; odds are one or more has popped. This is not major at all if this is the problem.
Most vehicles now have these links located in an underhood fuse box, depending on the type of vehicle.


Thanks, I checked the fuses, but they looked okay. Are the fuses the same thing as the fusible links? There is a fuse on the positive Battery cable that looks like it may have popped.


Fusible links look like regular wires, only thicker. That is, along a wire that is as thick as a tootpick, there will be a section that is about 3 times as thick. They are usually short (2-4 inch) sections of wire between two plugs so they are easy to replace. Usually they will burn or at least discolor their insulation when they fail. Fusible links are commonly found near the alternator and starter.

I am surprised that you needed all the replacement parts that you have already replaced. People reverse jumper cables all the time with minimal damage. The worst fear is cooking a computer.


To avoid this happening again, buy a set of those new fool-proof cables. I bought my wfe a set; no matter how you hook them up, they provide the right polarity!


You don’t say what kind of car you have. I did this once on a car whose voltage regulator was not part of the alternator. The voltage regulator started smoking and I immediately unhooked the cables. All I needed to do was replace the voltage regulator. If you tell us what kind of car it is, we might be better able to help.


I don’t disagree with anyone but it seems that if the lights do not come on unless the car is running, you have a couple wires melted together or shorted out. The circuit for the lights must be inoperative with an open in it or blown fuse or relay, plus it must be attached to another circuit that is on only when the car is running. Otherwise how would the lights get power? I think you are going to have to look at all of the wires in the harnesses under the hood and under the dash to check them or have someone do it. It would help if you had the wiring schematics in the factory manual to id the wire colors etc. You can id the circuit powering the lights by pulling fuses one by one till the lights go out which will help narrow the possibilities.

You know, it really is easy to get the polarity reversed since you have to look at the black + and - on the battery. Red cables start to look black after some age. I just don’t jump batteries as a rule.


Depending on the type of vehicle some fusible links are plug in plastic affairs and fusible links generally have a high amperage rating; 20, 30, 40 amp and higher, etc.
Generally the links are plug-ins or a short length of heavy wire as mentioned. The wire types are usually located at the battery positive terminal. In older vehicles they could be located along the firewall or branching off from the heavy cable lead at the starter motor.


You don’t say what model or year of car, so it’s hard to assess the damage. I’d say the radio is fried for sure and will need to be serviced or replaced. You didn’t say if you checked all the fuses. Do so if you haven’t. Recent cars use electronic control modules for all kinds of things, including the headlights & dash lights. I’d expect that you toasted a few things, including possibly the “body controller module” or BCM. If your car has ABS, you may have fried the ABS controller–this may light up the brake light, but it varies from mfr. to mfr. how warnings are displayed. I’d check the alternator, as the batt light coming on usually means this isn’t working. You’re lucky the car starts—apparently the PCM (car’s main computer) wasn’t hurt or has built-in protection. If everything on the car will work, albeit haphazardly, it’s not likely in my opinion that you have burnt up fusible links. Sorry.