Grease at Electrical Terminals Ace Electrical Product Department Should an insulating (dielectric) grease be used at electrical connec- tions? Ace Electric received a memo asking this question. The memo stated, “Silicone is an insulator and a terrible conductor.” It mentioned that some sug- gest a petro-leum-based grease. It claimed that if an insulating silicone grease is applied, there will be a poor electrical contact. For some years now, OEM’s have been utilizing special ‘greases’ during the assembly of electrical components and electronic devices. These specialty greases are applied onto, or around, mechanical electrical connections. Common automotive applications include high energy ignition, on insula- tor and boots, and wire harnesses, on end-terminals or connectors where mated to terminal blocks. These greases serve as moisture barriers to prevent oxidation and corro- sion and as release agents to allow for easier removal of boots and connectors. Some specialty greases, such as those applied to GM HEI, have ‘dielectric’ properties. A dielectric (non-conductive) grease is used to fill voids between insulators and conductors in an attempt to prevent ‘arc-over’ and ‘carbon tracking’; problems associated with high potential voltage circuits. The “grease” that Ford uses on the 2G(IC) and 3G IAR rectifier output plug (BBS terminals) is also dielectric. Though this plug typically sees only 14.2 to 15.2 volts, a voltage not usually considered as “high-potential,” it is sub- jected to heavy current flow. Whether it’s caused by atmospheric environmen- tal corrosion or loose connection arcing corrosion, high resistance between the conductors in this plug creates quite a problem. A tight fitting harness is a must here, grease is no substitute for a poor mechanical connection. There are petroleum-based greases and compounds being used for ‘dielec- tric’ applications. While there is room for discussion, a quality silicone-based dielectric compound proves to be more reliable for most automotive applica- tions. Originally used in the electronics industry to protect delicate instruments, silicone-based dielectric grease is effec- tively non-flammable, harmless to most rubber and plastic, and is an excellent lubricant. It holds up well under extreme heat and does not evaporate or bleed as do many petroleum-based products. Note: Don’t skimp when applying dielectric grease to spade terminal con- nections. Functionally good terminals provide a mechanical connection in spite of the amount of grease applied, by wiping clean during installation. Quality spade terminals maintain the integrity of their electrical connection by the spring nature of their design.