Current from a Boch relay

I want to know how much amperage the coil is going to use?   12V    and I dont know what the coil resistance is.       I have nothing hooked up, just wanted to know what they typically use as far as current .

The current draw by the coil of a bosch relay is ~0.160 amps. Most amplifiers draw at the most 1/3 of this just to turn them on. Also, they Bosch relay has low resistance. (Usually ~75ohms) So... a different relay will probably be your best bet just so you don't accidentally damage the headunit's transistor for the remote out. Look for a relay from Radio Shack. Its stock number is 275-248. It has a coil resistance of ~400 ohms which means that it will draw ~1/5 the amount of current of the Bosch relay. Also, look at protecting your head unit with a diode soldered on the relay. You can use Radio Shack part #s 276-1101, 276-1102, 276-1103, or 276-1104. You need to put this inline with the coil or the power terminals. Just make sure the positive terminal and the striped end of the diode are together before you solder. Do not connect the positive terminal and anode together. Hope this helps! Eric Lucas

I looked at that part number on the Radio Shack site.    How can you tell how many Ohms it has?   It doesn't say.      Its ok to use it in an automotive application?

The coil impedance should be listed on a product datasheet, though I don't see one for the Rat Shack relay. Or simply measure with a multimeter. Look at your headunit manual and see if there is a max current for the remote turn-on. I'd be surprised if it can't supply the ~160mA to activate a Bosch relay.

Sometimes the coil impedance will be listed on the packaging as well.