Car Stereos: Power Antenna Relay, fluke 87, power antenna

Question
I'm have a Pioneer aftermarket headunit (w/ CD) in an 86 Buick Regal with power antenna.  I also have an aftermarket Jenson amp running a pair of 10" subwoofers.  Vehicle was purchased with this setup already.  The headunit has a blue/white stripe wire coming out and this is the power antenna lead (+12V radio on, 0 volts when off).  Directions state to use this wire to power amp sensing wire (which is blue), which I am.  As stated the vehicle has a power antenna (pass. front inner fender mount) with its relay behind the in-dash glove box.  There is a blue/white stripe wire that goes from this relay for connecting to the headunit (label pwr. ant).  I discovered this wire was disconnected when cleaning up the underdash wiring and wanted to figure out if the antenna actually worked (was told it didn't work / broken so thought mast was broken).  I unhooked the amp sensing wire and connected the power antenna wire and it worked - the mast did not raise up all the way but it worked.

My questions are can I have the amp sensing wire and the power antenna lead connected to the +12V power antenna wire coming out the back of the head unit?  Also, do you know what the normal mA draw is on the relay for the power antenna (my chassis service manual doesn't state)?  Using a fluke 87 meter, the draw shows to be 187mA for the power antenna relay and 36mA for the amp when connected separately and 214mA when connected together (installation guide states do not have anything connected that exceeds 300mA to the headunit wire).  My antenna does not fully extend - only two sections extends then the motor shuts off - so only extends approx. 2 ft.  I feel the draw on the antenna is huge but the amp is in line with what it should be (others feel the same).  Could this be due to the antenna not fully extending and causing excessive draw?  Or is this draw normal?

Any help would be greatly appreaciated!! Thank you.

Answer
Hi Jae,

Assuming that you're testing the current draw through the activation wire, and not the main power wire to the antenna motor, then I think the current measurement isn't far from what I'd expect.  If the wire is triggering a relay coil, then a normal current draw might be anything under 200mA. I know a standard Bosch automotive relay is designed to draw 140mA through the coil when activated; it's possible that the factory relay in your car just has a slightly different coil resistance.  I doubt that it's related to the fact that the antenna doesn't extend fully; I can see that affecting the current drawn through the motor, but not through the relay coil.  In any case, I don't see any reason why you can't connect the power antenna and amplifier activation wires to the Pioneer deck's remote output.  If you install more amplifiers, though, you might need to add a relay to switch all your devices on and off.

Hope this helps!

Brian