Q: Electrical - car battery positive temporarily touched negative - where is the problem?

asked by on

2009 Mazda 6 4 cylinder Keyless ignition

When I was installing a new battery I accidentally touched the negative and positive cables to the wrong terminals for a second. The car horn sounded and it sparked. I quickly pulled the cables off and put them on the correct terminals. Now the car will not start, no lights, nothing. I Checked the battery and it is measuring 12.6 volts. I pulled the cover off the engine fuse box and noticed the main 125 amp fuse was blown. I disconnected the battery and installed a new 125 amp fuse. I reconnected the battery. Now the brake lights work and the horn works. However still no interior lights, radio, no sign of life on the inside. Also the front lights do not. I looked at the other fuses in the engine fuse box and the inside fuse box and they all appear fine. Is there another fuse outside of these areas that could be blown or something else I am missing?

My car has 50000 miles.
My car has an automatic transmission.

Reverse polarity, at the battery, in a 12 volt electrical system on a car can cause a variety of effects including damaging the alternator, diodes and the numerous microprocessors on a vehicle such as those in the powertrain control module (PCM). As far as other fuses, they are numerous not to mention fusible links, circuit breakers, and all of the individual electronic components themselves in many circuits that could have failed due to to reverse polarity. Inasmuch as the vehicle does not start, the simplest thing to do is diagnose the starting circuit first as, in the course of that, other fundamental failures (for example if the PCM was fried) will come into view. If you want these steps performed by a certified Mechanic, dispatched by YourMechanic right to your location, please request an electrical diagnostic and the responding certified mechanic will get this resolved for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. Electrical - car battery positive temporarily touched negative - where is the problem?

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Is there a constant 12-volt source from the fuse board under the glove compartment?

It does not appear that there is a fuse for the horn located in the interior fuse panel. I would probe the ignition and accessory power fuses to see if they are a constant 12-volt source. If one of them...

Q: I put a cold air intake on my car I have replace the O2 sensor that is failing area code p0151 I'm not sure what to do mass is new

Hello. If the P0151 code persists after replacing the oxygen sensor, then it may be possible that the issue is with the wiring. If there is any damage or wear to the oxygen sensor connector or wiring there may be...

Q: Dark green sludge

Hi, thanks for writing in. Dark green sludge is most likely grease from an outer CV joint boot that has split open on whichever side you are seeing it. If you would like help with the repairs, consider having an...

Related articles

How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.