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HOW-TO: Rebuilding / Refurbishing a Hirschmann Antenna

gerryvz

Site Honcho
Staff member
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.
IMG_6568.jpg IMG_6569.jpg


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.
IMG_6570.jpg


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.
IMG_6579.jpg IMG_6580.jpg


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.
IMG_6571.jpg IMG_6572.jpg IMG_6573.jpg IMG_6574.jpg


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.
IMG_6575.jpg IMG_6576.jpg IMG_6577.jpg IMG_6584.jpg IMG_6585.jpg


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.
IMG_6581.jpg


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.
IMG_6583.jpg IMG_6582.jpg


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.
IMG_6586.jpg IMG_6587.jpg IMG_6578.jpg IMG_6588.jpg IMG_6589.jpg IMG_6590.jpg


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).
IMG_6592.jpg IMG_6593.jpg IMG_6596.jpg IMG_6597.jpg


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.
IMG_6594.jpg IMG_6595.jpg


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.
IMG_6598.jpg IMG_6599.jpg IMG_6600.jpg IMG_6601.jpg IMG_6602.jpg


Here's what the assembled antenna looks like, just before the cover is pressed onto the bottom.
IMG_6603.jpg


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....
IMG_6604.jpg IMG_6605.jpg

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.

IMG_6607.jpg IMG_6608.jpg


Then you just press the top back onto the bottom, making sure all of the tangs engage their clips.
IMG_6609.jpg


After the two halves are mated, rinse and repeat with the Bro-shine on the BOTTOM HALF of the antenna case.
IMG_6610.jpg


Here are two views of the finished antenna, after the Bro-shine treatment.
IMG_6611.jpg IMG_6612.jpg


Next up is Part 2, which is the electrical testing and mast insertion of the antenna. Stay tuned !!
 

garrison

E500E Newbie
Thank you ... Thank you ... We have a pair of these that could use maintenance ... amazingly clear, concise and explicit directions and photos ... I appreciate the step-by-step ...

regards,

garrison
'92 400E @ 241k
'95 E320 @ 181k
 

gsxr

.036 Hoonigan™, E500E Boffin
Staff member
As discussed elsewhere on this forum, repeatedly, if you can still buy a new replacement Hirschmann from Amazon for $175-$190 delivered, save yourself a lot of time and hassle and buy new. Repair makes sense when they are NLA. There are many different failure modes, including some that cannot be fixed without cannibalizing another used unit, which adds more $$$ and results in questionable life span. The new mast at $75-$100 is the dealbreaker for me. Y'all do the maths yourselves and decide what's best for your car / budget.

UPDATE: As of 2018, it appears both early & late antenna assemblies are NLA from MB and almost all aftermarket sources.

:wormhole:
 

JC220

Active member
Gerry – great DIY! Just noticed yesterday that the power antenna in my new to me 320CE is ‘trying’ to work with the motor clearly running but clicking / jumping due to the mast being frozen up.


Going to take it out tonight and strip down to see what’s going on inside. If I’m lucky it will only require a new mast fitted in along with cleaning - re-lubing. Hirschmann do their own grease (And mast wipes which I already have) so I’ll use that maybe on re-assembly. I’ll update this thread on what I find in due course! I have 3 old frozen units that I can also steal parts from if needed.
 

nocfn

E500E Guru
I wanted to add some pictures of the gears, showing the common wear failure on OE. It is a stop or tab for the spring on the worm gear drive half. When this stop goes. There is no tension for the two halves to spin as one gear. I am sure this is for all cars, but mine is a 94 for reference. Antenna Source on Amazon was my place to go for IMO better plastic and design improvement. The new design has the stop molded into the plastic as part of the hub where the original is glued out on an island so to speak.

Photos below of broken originals. It was a “Good Death”. Last photo is replacement design:
 

Attachments

gsxr

.036 Hoonigan™, E500E Boffin
Staff member
Next up is Part 2, which is the electrical testing and mast insertion of the antenna. Stay tuned !!
We've been on the edge of our seats for 3.5 years, Honch! When is Part 2 coming out? You're not pulling a Tesla, are you?

:pc1:
 

gsxr

.036 Hoonigan™, E500E Boffin
Staff member
I don't believe these can be rebuilt and acheive any longevity.
It depends on the condition of the unit in question. I've seen multiple failure modes, the most common (IME) is the electronic circuit board which is fairly easy to swap out... if you have a good one to swap in, with unknown life span. The board could probably be repaired / rebuilt as it appears to be relatively simple. Guess I should hang on to the bad ones as cores to fix.

I've also seen physical failures of metal brackets inside the assembly, which renders the unit unserviceable, only good as a parts donor. The motors are USUALLY ok. If the mast moves smoothly and the gears are intact, a clean+lube may at least extend the life of the antenna. I expect we'll be seeing more action on this HOW-TO thread now that the complete new antennas are NLA. A few years ago it was a no-brainer to just buy a new one for $200.

:duck:
 

gerryvz

Site Honcho
Staff member
I have 10-12 parts antennae for my 126 and 124. For exactly that reason — electronics etc.
 
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