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power antenna doesn't go up (sometimes)


dmorlow
07-01-2004, 04:10 AM
About 4 out of 5 times I start my car, my power antenna works perfect. But about 1 out of 5 times I start my car or turn my radio on, my power antenna doesn't go up. I don't even hear the straining of the motor trying to make it go up. Anyone know what would cause this? The antenna, antenna motor, or maybe the radio? I haven't actually listened right outside the antenna to hear if it was trying to go up but my last car, if it was trying to go up, you could hear it from the driver's seat. I don't hear anything like that. Then it seems the next time or time after that, the antenna goes up with no problems. If the antenna was dirty or getting stuck, it seems like it might get stuck half way. It wouldn't just work or not work. How would I diagnose this to figure out what is the culpurit?

ugsrich
07-02-2004, 12:18 PM
I've reviewed the circuit diagram in my '95 service manual so I have a good idea of the circuit operation. I have also worked on a GM power antenna problem before and so I have a good idea of the physical device and it's electical switching to change the motor direction (extend/retract - How does it know?) at the atenna itself.

My question at this point. Before going any further with the antenna problem itself is: Does the radio come on even if the antenna does not extend? (Naturally the signal may be very poor, but does it come on at least with static or something?)

Let me know and I'll dig deeper in the operation of the device and we'll see if we can track it down. I kind of like these sort of problems...it's interesting to see the manner in which the devices are interlocked and controlled. Unfortunately, it can be difficult to get to some of the wiring and stuff to repair (that's the part I don't like).

dmorlow
07-02-2004, 04:18 PM
Yes... The radio does turn on. Just the reception is terrible (of course).

ugsrich
07-03-2004, 05:45 PM
I’m going to assume that when the antenna mast does extend as expected it rises to its full extension. I’ll further assume that you have cleaned it and lubricated it with a light lubricant (I recommend silicon spray, or silicon grease lightly applied).

My first guess, and the place I would go to first is the motor up/down switch that is located at the motor itself. (I’m not aware of your mechanical aptitude and I make no assumptions.) The switch at the motor is used to change the direction that the current will be allowed to flow through the motor. Through one pole the motor will turn in the “up” direction pushing the mast to its full extension. When the mast reaches its full extension and stops, the motor’s torque actually causes the motor itself to pivot and toggle the up/down switch to the down position. This does two things: 1) stops the flow of current to the motor, and; 2) places the up/down switch in the down position.

My guess at this point – and it’s only the starting point – is that the problem resides with the motor up/down switch. I somehow suspect that upon retraction of the mast the switch is toggled enough to break the mast-down power circuit but for some reason the switch [sometimes] does not move far enough into the mast-up position. This naturally begs the question of why is it intermittent? The only explanation I could provide is vibration causes the switch to move far enough into the mast-up position. (Sounds somewhat lame I know, but strange things go on in the harsh environment that our autos are exposed to.)

None-the-less, this would be my starting point. I would make sure that nothing is obstructing the motor/mast assembly in any way. It sounds to me as if for the most part things are working correctly between the radio and antenna as well as between the “hot” power source and the antenna.

I would do some examination of the unit and I would disassemble the mast/motor unit and clean and lubricate it. This would be my first action.

There is a relay that is part of the electrical control for the circuit. But, my “feeling” and that’s all it is, is that the problem is at the motor/mast assembly itself. That's where I would start based on the symptoms you've provided.

Let me know if you’d like some additional thoughts or diagnosis ideas.

dmorlow
07-03-2004, 08:27 PM
Ok, I haven't tried lubricating the antenna yet. See the way I am thinking, I don't think it is a problem with lubrication. Because either the antenna works or it doesn't. It never gets stuck half way. If it was a lubrication problem, it would seem it would get stuck half way once in a while. When it works, it works perfect. My last car, my antenna used to get stuck half way all the time. When it doesn't work, I don't even hear the motor straining at all like it doesn't have power.

ugsrich
07-04-2004, 08:46 AM
Based on your follow-up (and you probably already said that) I'm with you - I doubt it has anything to do with lubrication of the mast itself. So, I would turn my attention to the drive motor, the up/down switch, and the associated mechanism therein. The intermittent nature of the problem makes it a real bitch to diagnose and repair (I have a firm grasp on the obvious!).

dmorlow
07-18-2004, 06:44 PM
Well, since my last post, my antenna has completely quit working. It hasn't worked for a few days now. I am just getting used to having a really quiet ride. It's kind of relaxing driving without the radio on. But I am starting to notice a lot of squeaks and noises that I couldn't hear with my radio on. So, to end my pain and suffering, I need to figure out why my antenna doesn't go up anymore. But I found an auction on ebay for an antenna. I am bidding on that. I am broke and can't afford a new one. (I am a poor college student.) If I win the bid, I'll see what happens. (If it fixes it.)

dmorlow
07-24-2004, 07:57 PM
Ok, I finally just bit the bullet and bought a new OEM AC Delco antenna for $100!! But it fixed it. The new antenna works perfect. So it was the antenna dying all along.

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