Usage:
637D, 637D (PP) Tractor-Scrapers
Description of Change: New wiring groups are used on 637D and 637D (PP) Tractor-Scrapers. The new groups have a separate fuse for each electrical circuit. This permits easier diagnosis of any electrical problem for faster, easier service work. The new system does not have an in-seat start switch for the scraper engine, so this engine must be started at the rear of the scraper.
Adaptable To: The new wiring is in effect on 637D Tractors with Serial Numbers 26W386, 27W652 and 71W433. For conversion of earlier machines 26W1-385, 27W1-651 and 71W1-432, field replacement wiring groups have been released, but will not be available as complete groups; the separate parts must be ordered. For this purpose, a complete list of the group components is shown in the parts charts. All parts shown in both charts must be used together for conversion.
Special Instruction, Form SEHS7132, gives complete information for conversion, including installation of the new wiring on both the tractor and scraper. In reference to the special instruction form, a change has been made since the form was published. In the electrical schematic diagram on Pages 17 and 18, the coolant flow switches are shown as part number 4N9072. Change this number to 4N3899.
