I Just bought an fm transmitter and since i hate the stupid plug and all the wires i hard wired it to the car. first is this safe? also my power supply to the transmitter is always on even when the key is out. and the red LED on the transmitter is always on. My main question is, is it ok to leave it on all the time?, and will it drain my battery? i already did it to my sirius radio. My transmitter is a Monster brand one, i provided a link below for reference:
Hi, John. Although there aren't any technical specs available on the Radio Shack web site, I'd guess your FM transmiter doesn't use more than a watt or two of power. If you can remember to turn off your Sirius radio, it should use less than a watt when it's off.
Modern cars do have some current flow from the battery when the car's off, but it's small enough that it normally doesn't make a difference. Usually it's around 1/8A to 1/4A. It seems like you might have doubled that. It's still less than leaving a glove compartment light on. As long as you use your car every couple of days, and you've got a good battery, it shouldn't be a problem. Again, assuming you remember to turn off the radio.
I would be a little concerned about your wiring, though. You didn't mention where you hard-wired the radio and transmitter. I would hope it's to the original radio circuit, or the cigarette lighter circuit. But you should at least make sure your radio and transmitter are on a fused circuit. If they aren't, you could end up melting wiring harnesses and giving yourself a major headache if a wire gets nicked or something goes wrong.