1976 Cadillac power antena wiring issues

[Scot Minesinger]

The power antenna will not work. 

If I unplug the connector and apply battery voltage to the antenna with a #12 ga copper wire touching positive battery post it works perfectly.  If I measure the voltage from the unplugged side of the connector that is supposed to be giving the antenna power it reads 12 volts, so ah ha you think it is the connector - no.  Made a new connector and it will not raise or lower the antenna.  With connector plugged in I was able to read the voltage is 2.4 volts under load.  The wires powering the antenna are 18 or 16 ga. 

The radio is not original and was added about five years ago.  I repaired the air conditioning and replaced programmer and when customer came to pick up car (after leaving) he noticed the power antenna did not work.  When the radio is turned on it also turns on an interior light, and when power is connected to the antenna relay the light turns on - maybe antenna and light are in series??

With antenna powered by 16 or 18 ga wires the voltage drops to 2.4 volts.  With antenna powered by battery with 12 ga wire it works perfectly.

What in the world do you think is going on here?  Bad antenna that needs more power to work than normal?  Bad wires? 

The fuses, relays, and switches are all good.

[cadillactim]

Scot

With it being an aftermarket antenna, the wiring from the antenna relay and antenna switch could be causing the path of electricity to change.

Originally, when the radio is turned ON, the relay is energized which sends power to the GREEN wire going into the antenna.  The green wire is part of the LIMIT SWITCH in the antenna.  With the green wire energized, the antenna raises about 12 inches, part of the limit switch trips, then power leaves the antenna through the RED wire.  The red wire feeds the dash antenna switch.  When the switch is moved to UP, then power goes through the BLACK wire which raises the antenna until either the limit switch again trips which shuts the antenna off (antenna stays up), or will just partially raise the antenna until it is all the way up.  When the dash switch is moved to DOWN the WHITE wire will lower the antenna until it is all the way down, which would again trip the limit switch.

When the radio is turned off, the relay is de-energized, and power is sent through the WHITE wire which lowers the antenna until the limit switch again trips and shuts off the antenna motor.

In a nutshell:

WHITE wire - has power when radio is OFF. (limit switch shuts power off to motor when antenna is all the way down. When red wire has power then white wire has power when dash switch is in DOWN position)
RED wire - has power when radio is raised 12 inches. (limit switch sends power from green wire to red wire when antenna is up 12 inches)
BLACK wire - has power when dash switch is in UP and red wire has power.
GREEN wire - has power when radio is turned on (relay energized. Limit switch initially sends power to antenna motor, but once antenna is up 12 inches limit switch shuts power off to motor and transfers power to red wire)

The limit switch sends power from green wire to red wire, and also stops power from going to motor after a preset number of revolutions of the motor, both in the up and down directions.

All this being said, the way the aftermarket antenna has been wired to the original wiring can affect power to the antenna motor and the lighting controlled by the body grounds, etc.

Of course if the customer wants a factory antenna I have those rebuilt.

Tim

Tim

[Scot Minesinger]

Tim,

The antenna is factory, the radio is aftermarket. 

Thanks for replying to this.  I did not feel like making a killer puzzle so I left out the part about the interior lights turning on when antenna was attempting to be raised, so I need to fix that too.  Looks like I need to see how they wired that aftermarket radio.  The antenna works, if I bypass controls.  The problem is in the wiring of the added aftermarket radio.

Might call you Monday about the interior lights if I don't figure it out Sunday.

Thanks,

Scot

[TJ Hopland]

Looking at the radio seems like a good place to start.  Some aftermarket radios have an antenna and light hookup.   So this means they have ground, always on power, power on with key, dash lights, antenna.     Plenty of ways for a typical installer (most not very smart) to go wrong there.   If its a fairly new radio maybe they don't have the light connection anymore.     

[cadillactim]

Scot

When the radio is turned on, the antenna relay is energized.  I think it is an orange wire, but not sure. The energized relay sends power to the green wire.  When radio is turned off, relay is de-energized.  Make sure the relay is being energized.

Sounds like the wire they spliced into is also part of the interior lighting, and when the antenna motor runs it allows a ground path which makes the lights come on.

Tim