Electric Aerial Not retracting

[74merc]

Hi
The electric aerial on my E320 coupe is not retracting. What is the best way of verifying that the problem is in the aerial rather than at the head unit? I can hear a faint click from the aerial when the head unit is switched off which I assume is a relay.
Cheers.

 

[grober]

You probably just need a new mast but can't tell without a closer look. Does the AERIAL motor run at all and will the mast go down with a little "manual encouragement"?

http://mbclub.co.uk/forums/showthread.php?t=15560&highlight=mast+replacement

 

[74merc]

Thanks grober, the mast is ok, it was replaced recently. It sounds like the motor isn't running. I've checked and it's getting power OK but don't know if the motor is burnt out or it isn't getting a signal from the head unit to retract.

 

[Ted]

Leccy aerials usually work by the relay applying 12v across the two wires to the motor to make it go up, and then 'reversing' the voltage to make it go down e.g. imagine a red and blue wire from the relay to the motor. To extend the mast you would have +12v on the red wire relative to the blue wire (NOT necessarily 12v relative to earth), and to retract the mast, the relay changes over and applies +12v to the blue wire relative to the red.
If you don't have a voltmeter, I would suggest putting a test light across these two wires, and checking to see if it lights up both ways (up and down)
If it does, I would suspect the motor/mechanism. If it doesn't, I would suspect the relay or supply (or earth) to the relay.

Some aerials have the relay built in. This will make it a little more difficult.

 

[grober]

There will 3 or 4 wires leading to the aerial if its a standard Hirshman.
red------ 12v live supply
blackor brown-- earth
blue ---for some types of mobile phone

white----signal wire from radio

this is confusing because blue is normally the colour code of the signal wire from the radio end of things. Take a look at the connector on the mast motor unit and check the various pins for voltages with a multimeter as Ted suggests .
red--- ignition on for 12v
white radio on off with ignition on

 

[74merc]

Thanks all, yes there are 3 wires going into the aerial. 1 red, 1 black and 1 white, I wasn't sure what each one did so that makes it a bit easier. I have another head unit which I could try before splashing out for a new aerial. 100 quid seems to be the going rate for a replacement. I've seen universal Hirschmann replacements for about 50, anybody tried one?

 

[television]

with only 3 wires, then the relay energises to keep the aerial up when on and down when off, so one of two things, the relay or the motor, i would have said the relay is more prone owing to the arcing when turned off

 

[grober]

EURO CAR PARTS OFFER A HIRSCHMANN FOR £46-11 PLUS VAT but listed as not in stock at moment. Worth giving them a phone??

 

[74merc]

Thanks, I'll try ECP first. GSF and KMS also have replacements listed. First I'll ring a dealership to get an idea of price.