A common issue in classic cars is malfunctioning backup lights and starting difficulties. This often points to a problem with the starter neutral safety switch (NSS). This switch prevents the engine from starting unless the transmission is in park or neutral, ensuring safety. Let’s explore how the NSS functions and troubleshoot common problems, focusing on adjusting the switch for proper operation.
Starter Neutral Safety Switch Function
The NSS is a critical safety device that prevents accidental starting while the vehicle is in gear. It works by interrupting the starter motor circuit unless the transmission is in park or neutral. When the gear selector is in either of these positions, the NSS completes the circuit, allowing the starter to engage. A faulty NSS can manifest in several ways: the car may only start in neutral, not start at all, or the backup lights might not function correctly.
Troubleshooting a Malfunctioning NSS
Diagnosing a faulty NSS often involves checking continuity with a multimeter. This involves testing the switch in different gear positions to ensure the circuit completes only in park and neutral. If continuity tests pass but the problem persists, the issue might lie in the switch’s adjustment or the linkage connecting the shifter to the transmission. In the case of a TH400 transmission with a column shifter, a common problem is insufficient travel of the shift linkage to fully engage the NSS.
Adjusting the Starter Neutral Safety Switch
The NSS often requires a specific amount of travel to activate the contacts for starting and backup lights. If the linkage doesn’t provide enough travel, the switch won’t engage properly. One potential solution is adjusting the turnbuckle connecting the steering column to the transmission. Lengthening the turnbuckle can increase the travel distance at the column, potentially providing the necessary engagement for the NSS. However, it’s crucial to ensure proper adjustment to avoid misalignment or damage.
Finding the Right Neutral Safety Switch
If adjusting the linkage doesn’t resolve the issue, the NSS itself might be incorrect for the application. Different transmissions and column shifters require specific NSS units with varying travel requirements. Researching the correct NSS for a TH400 transmission and Flaming River column shift is essential. Comparing the travel of the old NSS to the new one can help determine if a different switch with a longer throw is needed. Remember to consult the vehicle’s service manual or a qualified mechanic for specific adjustment procedures and switch compatibility.
