Electric car aerial connections ?

[MIG Wielder]

I got a replacement electric car aerial last year from one of the independant traders.
Good bargain except I'm having trouble getting it to work.
It seems to have wire colour codes unlike any other listed on the various Internet sites.
There are 3 wires coming out of it plus the coax with the new style R.F. connector.
The coax is nicely earthed and checks out as 0 ohms with the voltmeter.
The control 3 wires are........
BLACK. I reckon this should be earthed to the car body earth . And this check out as connected O.K. with a needle-probe.

This leaves a RED wire fused at 5A. Fuse is O.K. but shows no continuity to earth or the BLUE wire.
And a BLUE wire , unfused which shows a resistance of 230 ohms to ground.

Putting +12V on this BLUE wire makes the aerial give a click as if a relay is operating, but nothing else.
Putting +12 V on the red wire does nothing.

Now the radio had a 3 wire control from a relay.
RED, which goes to +12 V always live but goes to 0V when the radio is on.
BLUE, which goes to +12 V when the radio is turned on.
There is also a yellow wire that connects to ground when the radio is on.
Intuitively I suspect RED to RED, BLUE to BLUE and ignore the yellow.
But since I can't get the aerial to work with a +12V wander lead I think it may be dead .
Any ideas please folks ?
Ta,
Tony.

[DavePoth]

Have you tried hitting it with a hammer?

Seriously though, if it's been sat idle on a shelf for years there's a chance that the motor may be a bit corroded, so hitting it a bit might free it up...

[Spunkymonkey]

I could be wrong but on an educated guess I'd suggest this:

Red (fused) as a live (ignition "accessory" switched) supply. Black as earth, blue as sense (connect to blue from radio).

The areial almost certainly has it's own internal switching that goes like this:

When blue is disconnected the red and black wires connect to the motor to wind the arial down. When it's fully down a limit switch between the relay and motor breaks the live connection to stop the motor.

When the blue goes live, the internal relay switches the red and black wires to connect the motor the other way, with the live going through a second limit switch which breaks the supply when it's fully extended.

Remove the live to the blue and the red / black connections swap back again to retract it.

When it's fully extended or fully retracted the red (live) will show no continuity because the limit switches have disconnected it.

Just a guess mind



To test that theory, connect your meter between red and black then apply 12 volts between bluje and black. You should then see continuity with a few ohms (the motor resistance) between red and black. When you remove the 12v feed to blue the continuity should disappear.

If that works, and as long as there are a few ohms (probably around 5 - 10 or so) resistance between red and black when you apply power to blue then try again with red and black attached to your car battery. Just flash the blue briefly to live and the aerial should start to move. If it does then hold the blue to live till it's fully extended then disconnect blue and it should retract.

[tinweevil]

I doubt it's that complicated, the aerial will deal with reversing the motor supplies not the radio. The fused red line should go to a permanent +12v supply not an "accessory" feed. it needs a permanent supply so that it can finish winding down after you've jumped out and walked away. As said limit switches in the aerial will confuse meter readings.

So I would say
Black - car ground
Red - car +12V (don't bother connecting at the radio unless it's convenient to do so)
Blue - sense or control, connect to the blue from the radio.

If you find that the aerial is up when it should be down and vice versa connect the aerial blue to the radio yellow instead of radio blue.

[Spunkymonkey]

The fused red line should go to a permanent +12v supply not an "accessory" feed. it needs a permanent supply so that it can finish winding down after you've jumped out and walked away.

Good point, Batman

Other than that we seem to agree even if I did make it sound a little over complicated. I was trying to suggest how to check before wiring it in but it always seems hard to actually explain what you'd normally do on auto-pilot with checks like that (and it's a long time since I wired an electric aerial - like, about 1990)

[MIG Wielder]

Hello All, Thanks for that. Yes you are quite correct. The aerial has internal switching so yes, Red to permanently live, black to earth and blue to the control signal . My confusion was caused by the existing set-up having a relay by the radio to control the up/ down of the old aerial.
Cheers All,
Tony.