Stuck at half-mast

  • Step 1: Extract the problem part
  • Step 2: Dissect and diagnose
  • Step 3: Fix the bits
  • Step 4: Reinstall the unit
Date:26 April 2012 Tags:,

Telescoping antenna masts are almost extinct, but if you have one, it will eventually need to be fixed. By Ben Wojdyla

Electric-powered, self-extending antenna masts used to be a telltale sign of a fancy, feature-laden car.

As is the case with many electromechanical parts, however, power antennas usually end up requiring repair. Run through a carwash with one extended and you’ll have what looks like a bent hanger sticking out of the fender. Today, power antenna masts have been replaced with fixed antennas or wires embedded in windshields, but there are still plenty of cars out there with these telescoping menaces. Broken antennas get stuck all the way up, all the way down, or often somewhere in between. The shabby appearance of, and stunted radio reception on, an otherwise perfectly good car means that replacing or repairing an antenna is a worthwhile fix.

It’s almost too bad these have gone out of style; they are actually pretty elegant in a Heath Robinson kind of way. An electric motor hidden below the fender turns nylon gears that eventually mesh with a toothed nylon rope matching the gears. That rope extends all the way through the hollow antenna sections and mounts to the tip. As the motor turns the gears, the rigid rope is pushed or pulled and the mast advances or retracts, stopping based on either a digital counter or timer or on a measured spike in voltage when the motor can’t turn any more.

As you might imagine, there are several ways these antennas malfunction. The most prevalent is a bent mast – even slight tweaks to the tight-fitting telescoping tubes can cause havoc.

The nylon bits are a problem, too; teeth from the gears or rope break off from wear or cold or the rope snaps along the length. Sometimes the antenna fails when the components just plain get dirty – rain and dust infiltrate the mechanism, and things grind to a halt. Below we’re going to walk through the general steps of removing the whole assembly, taking it apart, then cleaning and replacing the problem parts.

Step one
Extract the problem part
First, you’ll need to get to the mechanism. If the antenna is rear-fender-mounted, remove the boot trim panels to gain access. Front-fender units may be inside the engine bay or behind the inner fender. You’ll likely need a few screwdrivers and spanners. The mechanism is usually easy to remove – loosen any bolts and disconnect the earth strap, antenna signal wire and motor-control wires. Be careful with the connectors because they will be reused. Remove the assembly by pulling the antenna mast down through the fender.

Step two
Dissect and diagnose
Uncover the device’s guts by extracting the cover screws. Carefully remove the housing and gear cover, as the nylon cord within might spring out and fl ing smaller parts. Inside, you’ll see how the motor, gears and nylon rope work together. If the teeth on the rope or gears are stripped, you’ll need to remove all the broken pieces. There will undoubtedly be old, dirty grease that may or may not be the problem, but should be cleaned out. Inspect everything else for signs of damage; if a major part such as the housing or motor is broken, replace the whole assembly.

Step three
Fix the bits
If the telescoping mast is the problem, remove it by taking off the bushing at the top of the guide tube; it keeps the mast in place. With a firm grip, pull the mast out along with the nylon rope; pliers may be needed. Clean everything, including the gears, with a mild cleaner such as dish detergent. Lubricate the clean gears and housing with white lithium grease; it works well even at low temperatures.

Step four
Reinstall the unit
If new gears are called for, assemble them as before; most of the time they just drop into place. Compress the mast completely and run the nylon rope down the tube, then seat the base into the housing. You may need to tap it home gently with a hammer. Fully extend the antenna, then mesh the end of the nylon cord back into the gear drive and reassemble the cover and housing.

With the mechanism still loose, plug in the electrical connections, then turn the radio on and off. This should cause the gears to pull on the nylon rope and retract the mast. If the mast doesn’t go down, the gears of the nylon rope may not be properly aligned, so you’ll have to try again. Reinstall the assembly and bolt the mast bushing back in place. Now enjoy one less annoyance, at least until you forget to turn off the radio in a carwash again.

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