Postby dmtrmp6 » 08 Sep 2015 14:27
Warning: - incorrect wiring could damage the electrical circuits in your car. Always use a fuse in supply lines. No liability if you get it wrong. Please TEST the wiring on the bench first. Use properly crimped or soldered terminals, Insulate all connections with tape or heatshrink tube, keep all wiring away from sharp edges or moving items (seat runners, boot/trunk hinges, etc). ****** IF YOU ARE NOT CONFIDENT FIND AN AUTO ELECTRICIAN******.
Typical/common wiring for many (but not all) aftermarket electric aerials includes three wires:
Red = constant +12 v,
Black = ground/-12v and
Green (or blue or other contrast colour) is the switched +12v to raise the antenna.
The constant +12v (red) and ground/-12v (black) provides the power to lower the antenna and is always live (use a fuse). With red and black connected as above - applying +12v to the 3rd colour wire (green/blue etc) will cause the antenna to raise. *** Verify this on the bench before attempting any in car installation ***
Connect red to +12v (cigarette lighter cct perhaps) via fuse, black to chassis/car body/-12v and the 3rd colour wire to a switched 12v supply - this could be via a separate antenna toggle switch which needs to be an on/off switch. (Do not use a momentary on switch as the raise circuit would only run whilst the switch is held).
Note: Most modern head units (radio) include a switched +12v output (blue or blue/white wire) to activate a power antenna or amplifier when the radio/head unit is switched on. Be aware however that this switched output line is usually current limited as it is designed to provide the trigger signal for a relay (internal or external) to switch the main supply to the device/amplifier. It may be adequate to run the antenna. So switch radio on - Antenna raises, switch radio off - Antenna lowers -- MAGIC.
How does it work?
With antenna retracted (down) - constant +12v power on the red wire plus ground connected only, nothing happens. The application of power to the 3rd wire should cause the antenna to raise. The antenna normally includes an internal limit switch to break power to the raise circuit when fully extended. Removal of the power from the 3rd wire circuit (toggle the switch to off or turn radio off) will cause the antenna to lower automatically via the red and black wire circuit. A retracted limit switch would break the lower circuit when fully retracted. Reapply power to the 3rd wire (switch or radio on) will repeat the cycle.
If the output capacity (current/amps) for the switched supply output from the head unit/radio is inadequate then it could be used to switch a separate/higher current supply via a relay. Connect the output from the head unit to one of the 2 coil terminals of a relay, the second coil terminal connected to ground (-12v). Connect a fused +12v supply line to one of the relay switched terminals with the other switched terminal connected to the 3rd coloured wire on the antenna. Typical relay terminal numbers are: 30 - fused 12v supply line, 87 - 12v feed to the load, 86 - from the head unit output line, and 85 - ground/-12v. Again: be careful, be safe............
Hope this is helpful. Rgds, DM
