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castlesteve castlesteve is offline
Registered User
Join Date: Mar 2003
Location: Atlanta
Posts: 76
Rapid Turn Signal...

Anyone have this problem...

I usually diagnose problems pretty quickly, but this one is a little funny.

Model year: 1974

When the turn signal is NOT engaged, the flasher relay pulses randomly at double the normal rate.

The standard flash rate is duty cycle is determined by 2 circuits... the ON cycle is determined by the series resistance of the bulbs (about 500 ohms)... and the off cycle is determned by the RC constant in the flasher relay.

The relay is engaged when it has a low resistance to ground (less than 1k Ohms)... but should be an open circuit when not engaged.

3 items are in parallel to engage this relay (the relay is used for 3 separate functions): turnsignals, emergency flasher and emergency brake engaged.

Most people have the 3rd item disabled as they have disabled the seat belt interlock...

Replacing the relay does not fix the problem... and the emergency brake switch also seems to be ok. There is one more switch on my diagram... the emergency warning switch. Anyone know where that is????

Sorry about the lengthy technical post... just trying to reduce the amount of questions.
74-1.8 (sold)
86-944 turbo (sold)
97-M3 coupe (sold)
Old 04-07-2003, 09:55 AM
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