Restoration Project
Andrew Atwood
The Instrument Panel
Part 10 in an ongoing series
Our last article dealt with major electrical systems on my 1963 200SEb Heckflosse. With that accomplished, I worked on the interior. The challenge with interiors – with their complicated wood trim, electrical accessories including the radio, and intricate gauge systems – is that the skills, tools and know-how are generally beyond the scope of an average garage restorer.
If that’s the case for you, my advice is to remove interior components carefully, take lots of pictures and then send the systems to appropriate specialists for repair and restoration. We have a saying at my shop: “We like it when clients work on their own vehicles; it creates more work for us.” Know your limitations and you will save money in the long run.
However, I’ve been working with cars for a long time, so I had some alternatives. With regard to the radio, “barber-pole” gauge cluster, and wood trim, I’ll tell you what I did and provide some tips that may be useful if you decide to do your own work on one or all these systems.
Restoring the radio and amplifier
I wanted to restore the original Becker Mexico radio and factory speaker amplifier that came with the car. To my knowledge, these had not worked since the car was parked nearly 30 years ago. The comforting thing is that Becker Autosound still specializes in these radios. Like most experienced service, Becker isn’t cheap, but its work is beyond reproach. You might also still have an old-radio repair shop in your town, but these are disappearing fast as their owners retire.
I’ve got some training in electrical systems, so I did my own work. Because it is very easy to destroy the tubes and components in these older radios if power is applied incorrectly, I set up a bench testing station using a 12-volt inverter as the power supply with an 8-amp fuse inline on the positive side. A 12-volt auto battery would have worked, but I wanted 12.5 volts uninterrupted during this test to provide accuracy. The fuse is critical to prevent application of power greater than the original radio can handle. I’m cautious that way.
In that period, the radio was separate from the amplifier, so I had to test both at the same time. Because the original speaker was rotted beyond repair, I used a donor speaker from an older project in my shop for testing. Now came the moment of truth. I turned on the power knob. Lo and behold, the radio lit up; I turned up the volume and …
Disappointment – no sound. But as I turned to my toolbox to look for my test light and digital test meter, the speaker crackled to life. I could have smacked myself: How could I have forgotten? After 30 years, the old tubes needed a minute or two to warm up. How quickly we forget these things in our modern digital age.
Excited, I attached an antenna. The tuning knob was a bit stiff, but I was able to get a station or two. Now to try out the infamous Becker Mexico automatic tuner, or “wunderbar.” It started to move and then stopped. Because I knew I had a working radio, I figured all it needed was a good cleaning and detailing to bring it to full working order.
This is where patience and delicate handling come into play. I used an electronics cleaner-spray, an aerosol keyboard cleaner and lint-free cloths, all readily available at hardware and electronics stores. The lint-free cloth prevents lint build-up that could contaminate circuits or even start a fire by contact with hot parts. The aerosol keyboard cleaner is preferable to high-pressure air from the shop system, which can easily damage delicate components. When cleaning the radio, it’s only necessary to gently wipe off all the tubes with the cloth moistened with the electronics cleaner, and then follow with the aerosol duster.
Reassembling the unit, I noticed a few damaged parts, including the plastic dial indicator and plastic tuning and volume knobs. I ordered replacement knobs and a reproduction display from Becker’s website, as well as OEM-quality German-made reproduction speakers. Using these goodies, I finished the reassembly and set it aside for later installation.
Barber-pole instrument cluster
Next was the famous barber-pole instrument cluster. Most of these old clusters are okay if the car was treated well. Unfortunately, my project car had been left outside for 30 years and the window seals were rotted, allowing moisture and dust into the cabin. Dust and grime had penetrated the cluster, which was going to require more than an exterior cleaning. I could have sent the whole unit to my preferred service, Dick’s Speed-O-Tach in Tempe, Arizona, but I decided to do part of it myself.
This is a job that needs to be done with care in a clean environment with lots of light and a good magnetic tray to keep all the little tiny screws and nuts from disappearing. Taking lots and lots of photos throughout the disassembly is essential, as it is very easy to lose track of what went where when there are a lot of tiny pieces layered inside.
Unlike more modern cars, these old Heckflosses use mechanical gauges instead of electronic, meaning the oil-pressure gauge has a a brass fluid line attached and the temperature gauge has a capillary tube attached. Both systems must be carefully removed intact and stored carefully to keep them from being kinked or pinched, which can make the gauge beyond repair. On the other hand, the fuel gauge is electronic and easy to clean and test.
Each of the gauges should be tested for accuracy before reinstalling back into the cluster assembly. My German-market car had the oil gauge marked 1, 2 and 3, representing metric bars. One metric bar equals approximately one atmosphere of pressure (14.5 psi and 14.7 psi respectively); U.S. gauges are marked 15, 30 and 45 respectively. I used a small hand pump to slowly pressurize the oil line, stopping to check the readings on the gauge at 15, 30 and 45 psi. Do not exceed 45 psi or approximately 3 bar to avoid permanently damaging the gauge. My oil-pressure gauge was spot on, even being more than 50 years old.
The water-temperature gauge is easier to test. Just bring a cup of water to a boil: insert a good cooking thermometer and the sender end of the gauge to ensure they read the same. Then watch the gauge as the water cools during the next 20 minutes to be sure both read the same all the way down to ambient temperature. My gauge was good to go.
Testing the fuel gauge requires a power source. I attached the positive lead of the gauge to the positive terminal of a 12-volt battery, ran a wire from the negative terminal to the fuel-sender unit, and attached a wire from the negative battery terminal to the sender mounting plate. As I moved the sender from full to empty, I checked that the gauge mirrored the sender position. That checked out as well.
Because I had no way of testing or calibrating the speedometer, I sent it over to Dick’s Speed-O-Tach to calibrate and clean. Knowing my limitations is what keeps me out of trouble: I ultimately avoid spending money fixing things I broke.
The last task was to install new bulbs in the gauge cluster. Just as with the taillight bulbs, it’s important to use the correct wattage. I have seen a few melted clusters in my days from over-eager owners trying to brighten their clusters with higher-wattage bulbs instead of a bit of elbow grease. With the cluster assembled, I set it off to the side for later.
Dashboard clock
Restorers often overlook the factory clock installed in the dashboard. Even if they’re cleaned, they often don’t work correctly – or at all. I have six of these old clocks in my shop; not one of them worked. Imagine that: 50-year-old clocks that don’t work. These old clocks were notorious for failing motors. The easiest fix is to have a professional service replace the internal movement with a new electronic gizmo, which is inexpensive and quick. Dick’s Speed-O-Tach got it done in a few days for under $200.
Interior wood trim and padding
Before I could reassemble the dash, the wood interior had to be tackled. This is a major project on its own: The W112s have 30 pieces of wood trim on the interior and most of mine were in pretty sad shape. The wood trim on most of these cars has been refinished once or twice and, most of the time, performed poorly – with the wrong color, as well. The original wood color can usually be found on an area of a trim piece that has been covered by another piece, where sun and air hasn’t reached. However, if you’re not going for an exact-original car, have fun and make the wood trim any color your heart desires.
My wood trim was half refinished at one time, but I was very fortunate to find that the wood dash face – and the four lower-door trim pieces above the map pockets – were virgin and untouched by molesting hands. The original finish was dark teak, which I thought was a rich-looking color that would complement the interior color I had chosen (to be revealed in the next article).
When I refinished the wood trim in my old Mercedes back in 1986, the wood was only 20 years old, still supple and in pretty good shape. My problem now was the wood trim in my new project was more than 50 years old, in very delicate condition and, in some cases, in several pieces. This was beyond my scope of expertise. I needed to call for help.
Only a few companies refinish wood automobile trim today, as The Star magazine noted in its September-October 2014 issue about Madera Concepts (see “Keeping Up Appearances,” p. 62). These services can be expensive, but the quality of work matters. However, my good friend Dave Duncan, a part-time gunsmith specializing in Old West guns with wood stocks, offered to strip and refinish the wood trim and repair all damaged pieces. His work was impeccable – and really appreciated.
On older Mercedes-Benzes, a cloth tape between the wood trim and all metal that touched the wood stopped the wood from making noise when rubbing against the metal dash and trim and prevented chrome-trim pieces from chipping the lacquer finish as they were tightened against the wood. I took many pictures of the myriad bits and pieces of tape. To replicate the tape, I used the same electrical cloth tape as on my wiring harness. That worked flawlessly and may actually be better than original: It will stay soft longer.
The three pieces of wood around each of the window openings on the doors did not use the cloth tape, but instead used small pieces of felt tape. Surprisingly, this is still available through your local Mercedes dealer or a local fabric or crafts store.
Be careful when attaching wood trim with the small chrome-trim screws that use the small cup washers – commonly called upholstery washers – that go between the screw head and trim. These will also stop the lacquer finish from chipping when the screws are tightened.
The dash padding was rebuilt by Just Dashes using factory style foam and vinyl cover materials.
In our next article, we’ll tackle seats and upholstery.
Regular contributor Andrew Atwood owns Atwood European Repair and Service (www.atwoodeuropean.com) based in Phoenix, Arizona.
Redoing the dashboard – requiring restoration of wood, electrical and radio components and delicate gauges – involves a matrix of specialized skills.
FROM THE TOP: All of the dash chrome was replated. Delicate wood components were refinished by my friend Dave Duncan. Cloth tape was applied to the back of dash chrome pieces. The radio was fully redone. My old dash pad had disintegrated into four separate pieces; it was totally reconstructed by Just Dashes using factory-style foam and matching cover materials.