In the last week I had problems with my power antenna (or power mast). At some point refused to retract.
Please be aware; if your power antenna is stuck immediately disconnect the power harness from the relay mounted on the antenna. Remove the liner to access the antenna and disconnect ANY of the two connectors attached to the relay. If your antenna does not locks to the end of the line (either fully extended or fully retracted) the battery will be drained (even if fully extended or retracted does not means is locked). Do not risk just disconnect one of the two connectors. If not locked the motor receives continuously power and will drain the battery (you can hear a low clicking sound once every 15-20 sec, that is the bimetal safety switch connecting-disconnecting the motor). Also the wires and the motor are warm to hot during this time (that is your battery draining).
How to remove the antenna:
You need to disconnect the electrical connections (power and radio antenna), the drain tube and unscrew (no 10 wrench) the ground wire screw (topside) and the screw holding the antenna bracket to the body (lower side). Then slide the antenna down (to clear the rubber grommet). The antenna comes out from the trunk bracket attached.
Common problems to the antenna:
1. Burned Antenna fuse (20A trunk compartment)
2. Sticky antenna relay
3. Broken nylon wire lifting/lowering the antenna mast
4. Worn gears (motor shaft or plastic spooling wheel – worm screw assembly)
5. Worn brushes
6. Burned/dirty locking contacts (part of the brushes assembly)
7. Sized motor shaft due to water intrusion
8. Burned motor
1 and 2 can be eliminated once the antenna is removed by applying 12V ([+] to pin A and [–] to pin B to extend mast or [+] to pin B and [–] to pin C to retract mast) on the small pigtail harness connector that goes from the relay to the antenna motor (to be seen in fig.1, is a 3 wires connector A – White wire, B – Green wire and C – Gray wire). Never connect power between A and C (direct short)
If the mast is moving then either the antenna fuse is burned or the antenna relay is sticky or wiring issue on the car harness.
3. Can be detected easily by trying to manually extend the mast, if it extends then the wire is broken.
Any issue from 3 and down require disassembling the motor and gearing.
In Fig.1 you can see the screw, clips and rivets holding the two halves of the motor assembly together. If the antenna was never serviced, from factory comes with rivets. You will need to drill the rivets out and replace with screws. In my experience ½ inch long M5 screws with 2 washers are the best (you need 3).
Should you do exploratory surgery first, to prevent the wire from coming loose from the gear, leave attached the plastic piece shown removed in Fig.2.
Drill the rivets, pop the 3 clips and unscrew the one T10 screw not holding the previously mentioned plastic piece.
In Fig. 3 is the inside of the antenna mechanism with the cover removed. Please note the mast will come loose once the case is split (as seen in fig 3).
Inspect for signs of worn gears on the worm screw assembly. Replace the worn piece, if the shaft is rusted and worn then the whole motor shaft has to be replaced. The motor shaft comes out from the plastic casing after you take out the brushes/lock & safety switches assembly. Inspect the brushes if worn replace assembly. The stator (the big magnet shown in Fig. 3 should slide out (just magnetic force hold it over the motor windings).
The shaft can be borrowed from ANY Delco power antenna motor used in various GM models in the ‘90s. Fig. 4 is showing the stator.
The stator can be reused (just slide-it in place over the rotor). Note on one side the stator has a small round rubber glued, that side should be on the bottom (the not seen face in Fig. 3). To slide the rotor in place squeeze the two locking switch actuators and lower shaft. Make sure the two bushings (acting like bearings) are oriented with the flat side UP. If the stator is rotated around the shaft with the wrong side up then the motor will spin with grinding noise, if the bushings are wrong side up the motor will spin slower (friction after tightening the two halves of the plastic casing).
If is only the plastic wheel then disconnect the hook attaching the nylon wire to the wheel (as seen in Fig. 5) and replace wheel.
To attach the two halves of the case back together unwind the nylon wire and position the wheel EXACTLY as shown in fig. 6.
Notice the notch called stopper, that notch can not be in the RED area. Can be positioned in ANY position around that green circle but better orient the wheel in the exact position shown in Fig. 6 with minimum nylon wire on the wheel (notice the hook that is the end of the nylon wire, less than ¼ of a turn).
Observe the small wheel on the cover (see Fig. 7). Make sure the wheel is oriented in EXACTLY the position indicated (the missing tooth should be towards the red line). That wheel is what stops the antenna when fully extended. If the wheel is randomly oriented the antenna will not extend all the way.
Lubricate with grease all points indicated in fig 3 and the area around the little gear shown on fig. 6. Do not lubricate the cable or the mast.
Slide the brushes/switched assembly over the shaft (as seen in fig 6 highlighted magenta). If brushes are loose re-gap as required, then put the cover back along with the clips and screws (replacing the rivets). At the same time make sure the round gasket over the nylon wire (seen in Fig 3 and 6) is placed in the correct location.
ALWAYS do a bench test of the antenna; apply 12 V as described above. Allow the mast to travel from fully retracted to fully extend (several times). Very important, you should hear a distinctive click at the end of the travel (in any direction). If no click, the shaft does not slides (up or down) disconnecting the power to the motor. You can observe the shaft sliding up or down with the cover removed (as seen in Fig 2.). If no distinctive loud click start all over (something is not assembled correctly).
Hope this will save you $50 or so.