Does this blinker have a rate?

May 29, 2011 12:13 AM

Is there a minimum and maximum rate for the turn signal frequency of a car?

Sometimes during traffic I notice that cars ahead of me have turn signals (the turn indicator) that go on and off slightly more quickly than mine. Is the minimum and maximum rate regulated by the NHTSA (or another national agency) or is it just left to automakers not to make it too slow or too quick?

Side benefit: does anyone know if there is a linear correlation between the price of a car and the slowness of the turn indicator? For example, a Toyota Tercel's blinker flicks on and off like a hummingbird's wing whereas a Rolls Royce turns on and off like a hypnotic blink.

Thanks!

posted by fantasticninety to Grab Bag (6 answers total)

I assume it would be part of each state's vehicle code. I checked a few; California and Washington don't seem to specify limits on the flash rate, but Massachusetts specifies for motorcycles that “Turn signal lamps shall flash at a rate of 60 to 120 flashes per minute.”.
posted by hattifattener at 1:08 AM on May 29, 2011

Best answer: The only thing I could find on nhtsa.gov is in this PDF, which only specifies a minimum flash rate:

(a) A flasher having normally closed contacts must open (turn off) within 1.0 sec. for a device designed to operate two signal lamps, or within 1.25 sec. for a device designed to operate more than two lamps, or
(b) A flasher having normally open contacts must complete the first cycle (close the contacts and then open the contacts) within 1.5 sec

Some state requirements (Massachusetts, Wisconsin) specify a rate of between 60 and 120 flashes per minute.
posted by zsazsa at 1:12 AM on May 29, 2011

Best answer: The relevant document seems to be SAE J590b, which specifies 60 - 120 flashes per minute, with 90 being the ideal, but unfortunately standards aren't free so you'd have to pay to get a copy.

However, keep in mind there are essentially three kinds of flashers: bimetallic/thermal, hybrid, and solid state. The bimetallic kind (the oldest and most primitive) will vary their blink rate substantially with temperature and battery voltage. And the hybrid and solid-state flashers have a feature where they blink twice as fast if a lamp is burned out. So your Tercel may have either an old style bimetallic flasher that's a little bit out of spec or it could have a burned out lamp somewhere.
posted by Rhomboid at 1:21 AM on May 29, 2011 [2 favorites]

This is more common in motorcycles than in cars, but switching to LED turn signals without adding an inline resistor can cause turn signals to flash WAY too fast. You might be seeing the variation permitted within the SAE specification, or the drivers may have modified their cars.
posted by workerant at 5:47 AM on May 29, 2011

Also note that on most cars, if a turn signal bulb is burned out, the good bulb at the other end of the car on that side will flash much faster than normal.
posted by Kirth Gerson at 7:31 AM on May 29, 2011 [1 favorite]

On the linear correlation thing: if it exists, it's certainly not precise.

Carmakers like standardized parts--there's a good chance that Toyota Tercel uses the same flasher relay as that year's Lexuses.
posted by box at 12:27 PM on May 29, 2011