Electric antenna question...

[Steve W]

I am trying to find out why my electric antenna doesn't work. The actual antenna itself works...better reception when its up, but it doesn't go up or down electronically with the radio switch.
(My car has not only the stock AM-FM, but an aftermarket CD below the dash).
The standard radio in my car works when it has the antenna hooked up to it, but the switch that is supposed to raise and lower the antenna does neither.
SO,,,I got out my handy little tester, and un-plugged the connector from the antenna connection just to see if its getting power...and when its set at '20'...like when I want to test the alternator, there is no reading....however, when I choose a lower setting, it registers a little.  When the tuner button on the radio is pushed or pulled, the antenna is supposed to go up or down. How much of a reading should I see on my tester to know if the switch is good or not?

[TJ Hopland]

I dont have a 68 manual.   If its like the later ones its sort of a weird circuit because the radio is supposed to control the up and down but the switch was supposed to allow you to trim the height for optimum tuning.  There is some back and fourth between the motor and its limit switches, the relay, the switch, and the radio.  It only takes 1 bad connection in that whole chain to stop it.  Check your service manual for the electrical drawing or if you dont have one maybe someone can send you one.

A digital meter is very sensitive,  especially on those lower (MV) settings.  It can read voltage through the insulation of the wires so a tiny reading when you are reading a bundle of wires in a live harness is normal.  That antenna circuit is regular 12V so the 20V scale would be the one to be on assuming the next lower one is 5 or10.     

[Cadillac Tim]

The 68 power antenna does not have limit switches like the 73-up antennas.  There are only two wires going to the antenna.  One makes the mast go up, the other wire makes the mast go down.  Inside the factory radio is a switch, and when you pull on the tuner knob voltage is sent to one of the wires making the antenna mast go in the one direction.  When you push on the tuner knob, voltage is sent to the other wire, making the mast go in the other direction.  The antenna is grounded through the antenna housing through the fender.  So when you use your voltmeter, check for voltage at each wire when you push and pull on the tuner knob.  Should have battery voltage to only one wire at a time.

You mentioned you had an afermarket CD player.  Make sure you still have battery voltage going into the factory radio along with the antenna wires going into the top of the radio.

When the mast is at full top or bottom you will here a "click, click, click..."  That sound is the clutch in the antenna slipping and is normal.  When you here that sound simply release the tuner knob.

[TJ Hopland]

Interesting.   So with a modern radio you would need some sort of a timer to make the antenna work automatically. The modern radios (and I presume the 73+ factory ones) just give you a constant +12v when the radio is on.   

[Cadillac Tim]

The 73 and up antennas have a limit switch in the antenna that shuts the voltage off.  The dash switch is a manual override that bypasses the limit switch.  The older antennas are much more reliable and trouble-free.  They all have the problem of being bent or the cord breaking from age, but the limit switches go bad too often.