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Understanding SAE J590-1999: Turn Signal Flasher Requirements and Testing
SAE J590-1999 defines the test conditions, procedures, and minimum design requirements for turn signal flashers in 6V, 12V, and 24V systems. This standard is crucial for engineers designing automotive lighting systems, ensuring reliability and compliance with regulations like FMVSS 108.
Key Provisions of SAE J590-1999
The standard covers two main types of flashers: fixed-load and variable-load. Fixed-load flashers are typically used in passenger cars with two bulbs, while variable-load flashers are necessary for trucks or cars with trailers to handle varying bulb counts. Flashers conforming to this standard are identified by the code J590 per SAE J759. The standard also aligns with FMVSS 108, which requires detection of turn signal lamp outage except when variable-load flashers are used.
🛠️ Engineering Insight: Choosing the correct flasher type is critical. Variable-load flashers are required for applications with varying bulb counts, such as trucks with trailers, to maintain proper flash rate and comply with FMVSS 108.
Test Procedures and Conditions
The standard specifies test equipment per SAE J823. Key tests include start time, voltage drop, flash rate, and percent current on time. The flash rate and percent current on time must be measured under various voltage and temperature conditions. Below is a table for a 12V system as an example:
| Condition | Voltage | Ambient Temperature |
|---|---|---|
| a | 12.8 V | 24°C ± 5°C |
| b | 12.0 V | -17°C ± 3°C |
| c | 15.0 V | -17°C ± 3°C |
| d | 11.0 V | 50°C ± 3°C |
| e | 14.0 V | 50°C ± 3°C |
🔍 For fixed-load flashers, tests are performed with the specified ampere design load. For variable-load flashers, tests are done at both minimum and maximum ampere design loads. Start time measurements help differentiate between normally open and normally closed flasher types.
Design Insights and Common Mistakes
One common mistake is using a fixed-load flasher in a variable-load application, leading to improper flash rate or failure. Another is not accounting for ambient temperature effects during testing, which can result in invalid measurements. The standard requires testing at extreme temperatures (-17°C and 50°C) and voltage variations to ensure reliable performance.
⚠️ Warning: Using a fixed-load flasher in a variable-load application can lead to improper flash rate and potential non-compliance with FMVSS 108. Always verify the load requirements before selecting a flasher.
Frequently Asked Questions (FAQs)
- What is the purpose of SAE J590-1999?
- It defines test conditions, procedures, and minimum design requirements for turn signal flashers to ensure consistent performance across 6V, 12V, and 24V systems.
- How do you differentiate between normally open and normally closed flashers?
- Normally closed flashers have a start time defined as the time to open the circuit after voltage is applied, provided the closed circuit remains closed for at least 0.10 seconds. If the closed circuit opens in less than 0.10 seconds, it is considered normally open.
- What test conditions must be met for flash rate?
- Flash rate must be measured after five consecutive cycles, averaging at least three cycles at specified voltages and temperatures, such as 12.8V at 24°C and 11.0V at 50°C for 12V systems.
- How does the standard address lamp failure indication?
- In compliance with FMVSS 108, the standard requires vehicles to indicate the loss of one or more turn signal lamps, except when a variable-load flasher is used.
