Driver-installed Aux Jack/fm Transmitter Question

El Sabor Asiático

New Member
Nov 7, 2013
The seller of the '04 GT I recently bought had installed an AUX input jack in the (stock) stereo. The jack is connected to an FM transmitter, so you can plug in a phone or other audio player and play audio through a radio station. He installed an on/off switch as well, connected to the transmitter.

He said that he turned off the transmitter when not in use, because he was afraid of running down the battery. He said however that he wasn't sure if it would or not -- he just did it to be safe. Now, I am terrible about remembering to do this, and moreover I'm not sure (even less than he was) whether or not it's actually necessary.

I of course don't expect a definitive answer to this question, since I can't say specifically what he installed or how, but would welcome any educated guesses: would the transmitter be likely to draw power from the battery when the switch is left on, even if the car is turned off entirely and/or the stereo is turned off? Thanks in advance for any feedback.
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Not sure about that but if your radio reception is really bad then you probably know the culprit... I had one of those and it destroyed my radio reception so I couldn't pick up stations in the city that I was able to get from 20 miles away before... scrapped it and bought a new stereo...
Well if you really want to know if it is drawing any power while the car is off then do a parasitic draw test. It's a good idea to see if you have any accessory drawing power when it shouldn't. If you have a dvom set it to amps, your dvom has to be able to read less than an amp to a few amps. Check the positive side for a parasitic draw as well as the negative side. Too much to explain how but Google is your friend to find out how to do it. Turn on and off your transmitter switch and see if you go up or down in amps. Best way I know how to see if it drains the battery besides leaving it on and seeing if the battery dies. Also can't believe your stock radio still works, maybe it's time to upgrade with a unit that has aux and USB ports? Anyways good luck :)