IT IS HIGHLY RECOMMENDED THAT YOU ALSO REPLACE GLOWPLUGS AT THE SAME TIME (GLOWPLUGS & SMART START/TSU)...IF YOU HAVE BLOWN GLOWPLUGS AND YOU INSTALL THE NEW SMART START/TSU IT WILL SENSE IF THE GLOWPLUGS ARE WORKING OR NOT - AKA YOU MAY BLAME A NEW BOX FOR NOT WORKING. YOU CAN CHECK IF THE GLOWPLUGS ARE BURNED OUT BY OHM (TIP TO GROUND WHEN INSTALLED). ZERO OHMS MEANS BURNED OUT, IDEAL 1.8 TO 3.0.)
IF YOU CONTINUALLY BLOW GLOWPLUGS OUT THAT IS YOUR BOX SENDING 24V ALL THE TIME TO THEM AFTER THE ENGINE IS RUNNING, IT WILL START GREAT 1 TIME ONLY AND THEN THE PLUGS WILL BURN OUT...IF THAT HAPPENS YOUR BOX NEEDS TO BE REPLACED OR YOUR GENERATOR NEEDS TO BE REPLACED. (ENSURE THE "AC" TAP IS FUNCTIONING AT WIRE 2A REF SERVICE MANUAL, VOLTAGE SHOULD BE BETWEEN 9-16V DC - IF VOLTAGE IS NOT PRESENT GLOWPLUG SYSTEM WILL NEVER STOP CYCLING)
THE OLDER BOXES PUT "BRAINS" IN THE BOX UNDER THE STEERING COLUMN AND THE CONTROLLER IN THE THERMOSTAT HOUSING...THE NEWER SMART START BOX PUTS ALL THE "BRAINS" IN THE BOX UNDER THE STEERING COLUMN AND SENSES TEMP ONLY AT THE THERMOSTAT HOUSING (HENSE THE DIFFERENT TECHNOLOGY). TROUBLESHOOTING IS ENTIRELY DIFFERENT, THE MANUALS ARE WRONG/INCORRECT FOR REFERENCING THE NEWER BOXES, IT ALMOST ALWAYS IS BAD GROUNDS OR ENGINE WIRING ISSUES.