Poor Grounds Spell Trouble Column by Bob Thomas “The simplest }aame details are often those most ne- glected,” stated Mr. Murphy. I don’t know if he ever worked as a rebuilder, but many of his famous “laws” seem to apply to our business. The most common detail we all seem to miss on occasion 1s the in- ternal path to ground. This is something we all know, but think back about how many times you have been bitten by a poor ground connection inside a starter. Like the mysterious insect bite, maybe you have and never figured it out. Not every cranking motor is engi- neered like the Delco Remy 40-MT, with a huge post for the negative bat- tery cable attached directly to the ground brush plate. More often than not, the ground brushes in today’s au- tomotive starter are attached to the brush plate, which is attached to the commutator end plate, which gets its ground from the through bolts and field case, which get their ground from the drive end housing. Paint, surface rust and corrosion all cause resistance, as do poorly fit- ted or loose parts. Resistance in any series circuit is cumulative. It adds up. A little here, there and everywhere quickly becomes a whole lot. Always be assured you have a good path to ground. In the May issue of the Exchange Glenn Cheaney shared a lesson he had learned on the small Mitsuba starters found on many motorcycles, jet skis and ATVs. In case it slipped by you, the brush plate in this unit relies on tightly fitting parts for a good ground. Age, corrosion and cleaning all remove surface metal and suddenly the fit is not so tight. He explained how you could simply bend the ground tabs on the brush holder to assure you get a good ground and a satisfied customer. We all need every one of those we can get. I’d like to thank Cheaney for the tip. Many other starters rely on this same principle for a ground connec- tion. Denso and Hitachi have both made gear reduction starters with the commutator and brushes on the op- posite end of the motor from the end plate. A tight fit is the only way these negative brushes can ever get a good ground. The Hitachi unit in particular is popular with the high performance crowd because a conversion of it can be used on GM engines. Have you ever had a customer complain of lack of torque with one of these? Most of these units are installed on racing cars, which may sit idle for weeks at a time. The aluminum to steel connec- tion gets corroded and suddenly the starter fails to crank the big block en- gine when hot. It does not take much corrosion to cause a problem here. This brush holder has tabs that can be bent, just like the Mitsuba, and the mating surfaces must be clean. Some lawn mower starters and trim motors also use a similar type of ground connection. These starters fit equipment that is often left outside, rain or shine, and corrosion can be a big problem. Remember to assure a tight fit and a little dielectric grease on the connection should help cut down on the corrosion. Most of us like to paint our field AUGUST, 2001 cases since many customers judge the unit as much by appearance as per- formance. If you paint the commuta- tor end plates and the field cases to- gether, you will retain a non-painted contact surface for the flow of current. This is important to any starter that has the brush holder attached to the end plate. Also, the surface of the field case that mates to the DE housing should also be clean shiny metal. Perhaps all of this sounds a little elementary, but if you train yourself to think about the ground side of the cir- cuit every time you assemble a starter, you will become a better rebuilder and the quality of your starters will improve. It does not cost a penny more and it will save and make you dollars tomor- row. Bob Thomas is owner of B & H Electric, Jacksonville, FL. Page 1 of 1