Potential Repeat Disaster Prevented

[Tomnistuff]

I once almost burned my restored Ferrari to the ground when I idled the battery almost dead adjusting the fuel and spark (a weak charging system at idle), then drove it at high speed for an hour to go to a picnic.  Due to the really heavy battery charging at speed, the wires overheated and the electrical system caught fire in the engine compartment and inside the instrument panel, where the fuse box was.  I had the car towed, cleaned up the mess made by the extinguisher and replaced 100 feet of wire.  Not as quickly as I just made it sound.  I also redesigned the electrical system to use relays to control all the high power stuff – lights, charging, starting, etc.

Most early 60’s cars used few relays and often used Ammeters, routing high current into the passenger compartment.  Ours doesn’t use an ammeter but it does route high current into the rotary light switch.

Today, I was cleaning, inch by inch, my wiring harness before reinstalling it.  Surprise! Surprise!  I found that the red 10 gauge cloth wound wire from the rotary light switch to the alternator to the starter is frayed to the point of exposing wires, probably due to dry rot, time and heat, everywhere it exits the plastic harness protective tubing and at every exposed terminal.  I don’t know what it looks like inside the harness protective tubing, but I’m not going to take a chance.  Tomorrow, I am going to start to open the harness and remove and replace the big red wire, all 13 feet of it, this time with 8 gauge wire with modern insulation and add a 12 gauge fusible link before it enters the cockpit and attaches to the rotary light switch.  I would rather replace a fusible link than to clean the car after using a fire extinguisher.

It’s beginning to look like I may have to come to PUB 2015 in my 2014 C300.  I'll keep trying.

Tom Kizer

[Tomnistuff]

It's beginning to look like I was too subtle in my first post, now that there have been 145 views and no responses.

What I should have said is, "Those of you with Pagodas that have original electrical harnesses have wiring that is from 44 to 52 years old.  Mine is 48 years old and all it would have taken to burn it to the ground is for me to leave the lights on, have the battery go dead, jump start it, then get back on the road, thinking it will charge the battery on the way to where ever I'm going."

While charging the battery with a 55Amp alternator running at highway speeds can't be good for the battery, it's even worse on dirty, greasy, brittle, frayed, high resistance wiring that's trying simultaneously to charge a dead battery and feed the lighting system at night.

One is correct to carry a fire extinguisher in one of these cars, but it might not be a bad idea to carry a defibrilator as well.  I almost had a heart attack when my last one caught fire under the dash and under the hood at midnight on a lonely road.  The first thing that happened was that I smelled smoke and then all the lights went out

My wiring is almost done and although only some of it is new, the rest has been carefully inspected, cleaned, shrink wrapped and retaped.  It actually looks new, although it's still old and will bear watching. 

I think I'll also get a new fire extinguisher as well.  My lights-on warning chime is already sitting on the shelf waiting to be installed.

Tom Kizer

[66andBlue]

It's beginning to look like I was too subtle in my first post, now that there have been 145 views and no responses.
  ...  While charging the battery with a 55Amp alternator running at highway speeds can't be good for the battery, it's even worse on dirty, greasy, brittle, frayed, high resistance wiring that's trying simultaneously to charge a dead battery and feed the lighting system at night. ....

OK Tom, I have a question for you.
About two years ago you wrote about the challenges you had to install an "upgraded" 55Amp alternator in your 230SL and you were kind enough to post a source for the plugs that one needs to do so. http://www.sl113.org/forums/index.php?topic=17721.0
Are you now implying that this was a bad move and one should stick with the 35Amp alternator?
If there is no a/c in the car, does one really need the higher amp alternator? Or are we falling prey to the American mantra "bigger is better"?

[GGR]

I had the same issue on my '62 W111 Coupe. The fabric around the copper wire dissolved into powder with high risk of short circuit. I think on later cars MB went with plastic wrapped wires, so the risk is reduced, though plastic can also harden and become brittle. I do not know if this applies to the W113 though, as strangely, many upgrades that benefited the W111 Coupe during production years were not applied to the W113.

[Flyair]

Tom,
I hope that many of those who read your post went to check their installations. For our cars are not used regularly, the batteries are certainly subject to heavy charging loads. I think the risk of potential fire and heart attacks you described is relatively higher at the start of the season when the cars are brought to life after the winter season.

At list in my case this is an item I checked and thankfully thinks seem to be fine. And I will have it double checked by a mechanic at the next visit to the repair shop (there are always some stuff to fix, so it will be soon

[Tomnistuff]

OK!  I apologize.  You all got my message.

As we all know, accidents are usually the result of a combination of failures.  When a "sensitive" design is matched with a "special" usage, failures are not even required to have a problem.

As an ex powertrain engineer, I personally think that Daimler-Benz engineers were and are among the most thorough in the industry and their design cost, and the car price required to make a profit, illustrate it.  BUT, I doubt that many, if any, of those engineers would have imagined the number of W113s on the road half of every year and running well fifty years later.  We get spoiled by the quality and probably have too much confidence in those 50 year-old parts that we don't see regularly.

The "sensitive" design, still commonplace in the fifties and sixties was the routing of high current wires inside the passenger compartment.  It was changed across the board by most manufacturers in the late sixties, buy by then, some companies could foresee the end of their current product lines and decided not to redesign those cars.  Our Pagodas fit in that category, I imagine.  Anyway, with still "young" wiring, there probably were few, if any, failures of wiring.  It was probably failures of old wiring in 1930s and 1940s cars that drove the eventual change in the late sixties, I imagine.  The war stopped new car production for a few years and extended the use of pre-war cars until well after the war.

The unfortunate "special" usage that adds to the "sensitive" design is the fact that we tend to winterize our cars and put them away for up to half a year (especially here in Québec).  If we don't pre-charge our batteries, or keep them on a trickle charger, there is a risk that the combination of old frayed wiring, corroded connections and heavy charging of a mostly drained battery can be a problem.

I feel guilty that I didn't replace my wiring completely but these harnesses are really expensive and lots of work to hook up, especially the fuse panel, from what I see in the harness photos.

Anyway, I'll get off my podium and wish everyone a wonderful and safe Pagoda season in the Northern Hemisphere, and a peaceful and productive restoration season in the Southern Hemisphere.

Alfred, I'm still happy I've upgraded my alternator, especially since I'm adding A/C and higher power (slightly) headlights at the same time.  I'm unlikely to have a problem, since I've already caught one car on fire and know better than to charge a jumped battery with the alternator at road speeds.  I'll still not drive it without an extinguisher.

Cheers,

Tom Kizer

[Tyler S]

I had this thread in the back of my mind while trying to diagnose why my alternator would drop out with a load on it. Almost 2 ohms resistance between the battery and B+ alternator post. Removed the sub-harness between the terminal block and the starter and this is what I found. It was only obvious after I cut the black sheathing away. You can see where it got hot and melted the insulation. Ended up replacing it with a w126 chassis PN 1265400408 part. Its identical in every way except the B+ red wire is an 8ga instead of 10ga. Then replaced the other 10ga wire from the alternator to the terminal block. This area is definitely a bottleneck. Soldered all eyelets, heat shrink ends, and replaced sheathing. Now have a nice 13.4 volts with blower and headlights on. And the best part. I caught it before something tragic happened. Thanks to Tom Kizer, the original poster!    Tyler

[Tyler S]

Few more pics after harness repair

[Larry & Norma]

Just thought I would add my recent experience.

After opening the boot (trunk) the wires to the light in the lid had shorted due to
being folded one time too many. This should have blown the 8 Amp fuse but
unfortunately the PO had put a 25 Amp in its place. Luckily I got away with a melted
earth to the nearest point which was just inside the car from the boot (trunk).
Could have been so much worse.
The lesson learnt was check your fuses!

I found another that was 16 Amps