Semi OT- Automotive Turn Signal Flashers

fast

light.

(grounded)

the

socket's

MIT guys are so creative.

I was scratching my head trying to remember what brand of radio was in the Renault... my senior moment search engine finally just reported back: "Automatic Radio" ;-) ...Jim Thompson

On Fri, 25 Sep 2009 16:06:57 -0400, jeff_wisnia wrote:

: :My curious mind wants to learn the operating principle used in many :imported automobile turn signal flashers, the kind which increase their :flashing rate considerably when a turn signal bulb burns out. Their :flashing rate is inversely proportional to the load. That seems like a :good idea as it warns the driver that a bulb has gone s :outh. : :I had some Ss & Gs last night helping youngest son fix the turn signals :on his 95 Honda so he could pass state motor vehicle inspection. The :right side turn signals, both front and back, were flashing way too fast :and rather dimly too. : :The bulbs were the right spec and not burned out, so son soon reached :the limit of his expertise and sought my help. : :The front turn signal bulbs were dual filament 1157s with the "bright" :filament used for the turn signal and the "dimmer" one for the marker light. : :The problem turned out to be an open connection in the common (grounded) :lead to the front right bulb socket. : :So, with the marker lamps off the load presented to the flasher from the :right front lamp socket was the two filaments of that bulb in series, :going to ground through the three paralleled marker lamp filaments on :the remaibning three corners of his car. : :Fixing a corroded connection on the other end of the "bad" bulb socket's :ground lead cured the problem. : :So, without my having to obtain and reverse engineer a flasher, what's :inside it that makes its flashing rate inversely proportional to load? : :Thanks guys, : :Jeff

If you are referring to the older (but still very reliable) thermal-mechanical type of flasher unit here is an explanation for its operation.

While this text states right at the end that if one bulb is blown the flasher might not flash at all, this is not my experience. In all cases I have encountered blowing one bulb simply causes a higher flash rate. The reason as someone else has mentioned is, less current, less heat (but still sufficient to flip the switch), and therefore less time to cool before the next heater cycle starts, means faster flash rate.

their=20

=20

signals=20

fast=20

=20

light.

(grounded)=20

the=20

socket's=20

=20

I can provide you one from the early '70s; it probably just bimetal with the heater in series with the load.

many

increase their

Their

like a

signals

The

too fast

reached

"bright"

marker light.

(grounded)

from the

series,

filaments on

socket's

what's

load?

simply be

constructed,

with a

(And

lamps.

Yup. Used to provide about 5 V effective for the heavily damped dash gauges.

many

their

Their

like a

signals

The

too fast

reached

"bright"

marker light.

(grounded)

from the

series,

filaments on

socket's

what's

load?

simply be

constructed,

with a

(And

lamps.

=20

Yup. Good old 2n173 with autotransformer outputs.

many

increase their

Their

seems like a

turn signals

inspection. The

way too fast

reached

"bright"

marker light.

(grounded)

flasher from the

series,

filaments on

bulb socket's

flasher, what's

to load?

simply be

constructed,

with a

(And

why

switch.

lamps.

This

the

that

B+=20

the

far=20

car's=20

battery=20

Using simple indexing to access really large data stores gets ugly pretty fast. Try reading some early articles on reindexing data warehouses for data mining.