Fusible Link or Good Connection COLUMN BY RICHARD R. VENSEL We get many calls and this is one of the most common, “We just got another starter back and the brush has come loose from |} the field coil lead.” ! Or, “We just got another alternator back and the slip ring came unsoldered from the rotor coil lead.” What should we do? The table below tells the story. These problems were created by improper sol- der use. If you are like most shops, only one solder is used everywhere. Higher temperatures under the hood require a solder with a higher melting temperature, so if you want to use only one solder go with one rated at higher temperatures. To solve these problems once and for all, silver soldering would be the best solution. This doesn’t mean use solder with a little silver in it. It means using a silver solder composed of 80 percent copper, 15 percent silver, and 5 percent miscellaneous. A silver solder with this composition, whether it be ribbon or paste form, will start to get soft at 1190 degrees F. Note: Using silver solder requires a spot welder or a special silver sol- dering tool. It is easy to see how fusible links hap- pen; now it’s up to you to eliminate them. Richard Vensel is owner of Vensel Enterprises, Crystal Lake, Ill. Keep these points in mind as you replace brushes to your field leads and/or solder in an old or new slip ring: 1. Your soldered surface must be at least equal to the area of the brush lead or rotor coil lead. 2. Solder Composition Solder softens & begins to melt Tin % Lead % Copper % 40 60 0 361 degrees F 60 40 0 361 degrees F 97 0 3 430 degrees F