Originally Posted by SSEBONNE4EVA
We are seeing more and more battery drain problems due to faults in the power antenna.
Glad you found it. Some will retract and still drain the battery somehow if the limit switch goes.
I got my power antenna solved.
It has a rather bizarre mechanical arrangement for the limit switches, which requires that the motor and motor-shaft (and worm gear) be allowed to travel longitudinally....for a quarter inch or so, each way from its normal working position.
When the antenna reaches the end of travel and jams the motor, the worm gear still has to pull itself along for that quarter inch, dragging an arm to activate the limit switch. You can hear a click as it activates. If it fails to activate, power is applied to the jammed motor forever, which is the battery drain you are seeing.
Similar thing going the other way... a second arm, a second limit switch.
1. motor shaft frozen to the lower bushing.
2. gunk with old grease fills up the shaft channel and the motor can't easily travel longitudinally, so those arms don't move....... and/or
3. the limit switches have bent enough so that the arms no longer activate one or both.
The quality of the limit-switch contacts still looked okay after 13 years.
Cleaned out all the gunk and re-greased.... bent the limit switches a little more so that the arms will activate them earlier, and first tests look good.
It is a pretty tenuous arrangement for protecting against unwanted power drain... considering that it is "HOT-AT-ALL-TIMES" to the motor, whether the radio is shutdown or operating.
There IS an internal circuit breaker. Usually, in electric motors, thats exactly for preventing power when the motor is stalled, but obviously it does not do its job in this assembly. While testing, I had power to that motor while stalled a whole lot of the time, and the "circuit breaker" never blinked once....