Recently, I volunteered to provide one of the 500Eboard forum members with a used Hirschmann antenna for his car. I did not want to sell him a non-working antenna, so I took one of my parts antennas as a spare and then refurbished the primary antenna for him.
Basically this entailed opening up the antenna, confirming the proper operation of the antenna motor and rubber belt, lubricating the plastic gears, and installing a new MB factory antenna mast.
This is Part 1 of a two-part series on the disassembly, refurbishment, and testing of the Hirschmenn antennae that are found in the late ("facelift") W124 models, including the 1994 E500. It should also be heavily applicable to all other years of the E500E and W124 models, though the antenna may not be exactly the same on the inside.
Total time for a refurbishment should run around 1-1.5 hours, if you take your time.
In this Part 1 installment, we will cover the disassembly, replacement of needed parts, lubrication and general re-assembly of the antenna.
Tools required for this job:
- Medium flat-blade screwdriver
- Medium Philips-head screwdriver
- Small flat-blade screwdriver
- Needle-nose pliers
- Brake cleaner or other cleaning solvent
- Rags for cleaning (if needed)
Parts needed for this job:
- None, unless something is broken or worn out
- Good idea to have a similar/spare antenna on hand
Here is an overview of the antenna, as seen from the exterior obverse and reverse views. As you can see, the case is a bit dirty on the outside.
The first step is to remove the mobile phone box (the small silver box mounted to the aluminum antenna mast housing). This is held by one screw attached to a clamp, which is removed with your medium flat-blade screwdriver. Remove, and unplug the blue wire from the outside of the silver box. Then, using your needle-nose pliers, loosen the end of the black cable from the aluminum antenna mast housing, and unscrew it with your fingers. Set the silver box aside.
Loosen the set screw that holds the aluminum antenna mast tube to the plastic housing. Unscrew the aluminum mast tube from the housing. This will expose the aluminum inner mast tube. Pull this tube upward and straight out of the antenna case, and set it aside. It will likely have a rubber "foot" (grommet) and even a plastic tube in the bottom of the aluminum tube. if these don't come out with the aluminum tube, they are probably stuck inside of the antenna case, and you can remove them in a minute when you remove the top half of the antenna casing.
Next up, using your small, flat-blade screwdriver, CAREFULLY insert the end of the screwdriver into the slot between the two halves of the case, and prise gently outward. This will pop the small tangs out of their slots. Work your way around the case, and it should pop up as you go along. After prising away all of the tangs, carefully lift the shorter (top) half of the case off of the deeper part.
Here is a view of the interior of the antenna, immediately after the top of the case is removed. The close-up views show additional detail. Notice the rusty exterior of the electric motor. The motor was rusted and frozen, and the rubber belt and pulley was unable to operate the large plastic gear-set at the bottom of the antenna. Thus, this motor needed to be replaced.
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From here, you can carefully remove the two major components inside the case: the motor and gear assembly, and the circuit board at the top of the antenna. The motor and the plug that supplies power and signal to the antenna plug directly into the circuit board.
When you remove the motor assembly, make sure you remove the three little rubber feet that press onto the rounded pegs on the top and bottom of the motor (three on each side). Set these aside. The circuit board presses directly into two slots moulded into the sides of the inside of the lower half of the case.
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As you can see, the circuit board connections are quite corroded, necessitating replacement with a new circuit board in better condition. Make sure you photograph or write down the order of the wires that are connected to the circuit board.
The next step is to unplug all of the individual connectors from the circuit board, and then to clean out the inside of the two halves of the cases. I used a rag and some brake cleaner to do this.
Then, you need to replace the components that require replacement. In this case, I replaced both of the major components.
The photos below show the installation of the new circuit board, and the new motor/plastic gear assembly. These plug right into the new circuit board. As you can see, the contacts have very little to no corrosion.
Here's what the antenna looks like with the two major components installed. You need to route the wires carefully so they don't interfere with the insertion of the antenna mast housing tube in a later step.
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For the next step, you need to insert the aluminum mast tube into the body of the antenna. To prepare it, you need to make sure the rubber foot is inserted onto the non-hexagonal (rounded) end of the mast tube, and that the black plastic tube is also inserted into the end of the mast tube at the same end where the rubber foot is inserted (bottom of the tube).
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Then, CAREFULLY insert the mast tube downward into the antenna body from the top, and insert the rubber foot end down onto the motor assembly plastic housing.
After the mast tube is in place, then prepare the exterior mast tube for installation. This exterior tube is of a larger diameter, and it is threaded at the bottom and screws directly into the antenna exterior housing. Then, it is held in place with a Philips head set screw. Insert, screw down, and tighten set screw. Easy enough.
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Here's what the assembled antenna looks like, just before the cover is pressed onto the bottom.
Before the cover is installed, it's time to clean it up. A little brake cleaner to act as a solvent, followed up with a liberal coating of "Bro-shine," was just what the doctor ordered....
Not bad, eh?
While that Bro-shine is marinading on the top cover of the antenna, turn your attention to the gears, because it's time to lubricate them. I chose my lube of choice, the infamous "Gleitpaste". Using a small brush, work the Gleitpaste into the gears while working the belt mechanism with your fingers to rotate the gears in a 360-degree motion. Not much lube is needed -- just enough to get the gears wet with it all the way around.
Then you just press the top back onto the bottom, making sure all of the tangs engage their clips.
After the two halves are mated, rinse and repeat with the Bro-shine on the BOTTOM HALF of the antenna case.
Here are two views of the finished antenna, after the Bro-shine treatment.
Next up is Part 2, which is the electrical testing and mast insertion of the antenna. Stay tuned !!