Securing critical electrical connections.

[Roger Long]

My starter and alternator are currently out for inspection and repair. It was sobering and a bit frightening to take the starter off and find the wires loose on the the terminals. My starter is way down where it can only be seen or touched easily when the alternator and oil filter are off.

The heavy wires put a lot of strain on the little screw studs when the engine moves around on it's soft mounts. Even without that, it's a high vibration area. The big wire connected directly to the battery switch could create some real excitement if it came off and grounded itself on the engine block an inch away.

What is the best way to secure these screw terminals? Too hot, I think, for nylon insert nuts.

You mentioned something that all such connections should be coated with but I've forgotten what it is.

This would be a good time of year for one of your great tutorials about what you can do to increase the safety and performance of your electrical system short of rewiring.

 

[Rick D]

How about a double nut? I'll be interested to hear what MS says.

 

[Stu Jackson]

Yup, double nut and lock washer or star washer if you have the room.

 

[Maine Sail]

I use split washers for high heat areas but I check all nuts a few times a season especially the starter. Have yet to have one come loose. It is important to fully support the heavy wires so vibrations and flopping are not transmitted to the lug as easily. For starter cables I will often slit some heater hose to use a chafe protection then use a wire clamp to fasten and support it. It is best to use metallic clamps in engien spaces and the SS ones with rubber inserts are great for this.

I use nylocks for everywhere there is not high heat but they are ideally a one use nut as are spit washers but I see folks re-use them all the time. I always keep plenty of splits and nylocks on hand..

Double nuts are great but I have yet to see a starter stud that had room for two nuts and a heavy duty marine type battery lug. Even more difficult though is the access for two wrenches opposing each other to back lock them..

Just serviced some older Spartan tapered cone seacocks today on a 1979 Cape Dory and they use the double nut concept, like a stuffing box does. The problem is trying to get a 15/16" wrench and a 3/4" wrench on the nuts to back lock them while upside down with a gear box shifter bracket stabbing you in the back side.

As for terminal grease NoOxId is great but is a "potentially conducting" grease so you should be careful not to bridge across two terminals with it. I also use Silicone Dielectric grease, which is an electrical dielectric/blocker, for my battery posts and other areas. After a good clean connection is made I then coat it with the dielectric grease to protect it from oxidation.be aware that if you get silicone grease on the wire jacket nothing will ever stick to it in the future. This is the major draw back to silicone grease.

 

[woodster]

What about airplane....

starter cables...how do they secure them...i cant remember what we did when i was in army avation...but i can asure you they had some kind of a way to secure them......or you might try a cascagated nut ...

regards

woody

 

[Bill Roosa]

split washer and torque to specs. remember you are dealing with soft copper threads and presumably brass nuts so watch Conan-ing the things. Zip tie the cables so they vibrate with the engine and have one and only one place where they transition from engine to engine compartment (vibrating to non vibrating) and secure them there with lots of surface area and sufficient slack to keep all parties happy.
NEVER use the terminal stud as the start of a transition point. never secure the cables to the exhaust manifold and if you have to go near the exhaust manifold use a heat shield or reroute the wires.

 

[Bob S]

What do you think about Locktite?

http://www.mcmaster.com/#loctite-threadlockers/=c9vz83

 

[FourPoints]

I've always seen a double nut with a split lock washer between them as the typical starter cable arrangement on larger outboard engines and ski-boats, never heard of one of these setups properly tightened coming loose.