Blinker/Flasher Troubleshooting

Symptoms:

Flasher light on dash	Lights (outside car)	Result
On with no click	On with no flashing	bulb out or defective relay
On with slow click	On and flashing	bulb out or defective relay
On with normal click	On and flashing	normal condition
On with fast click	On and fast flashing	dirty light sockets or partial ground
On with fast click	Off and no flashing	short before wire gets to the turn signal circut under dash

Blinker Relay- (inside the car) two wires coming out;
light green/gray (to the B terminal) and light green/brown (to the L terminal)
The blinker relay looks exactly the same as the Hazard relay (under bonnet) and is located on the backside of the dash just under the tachometer on US cars.
Note that the Hazard and Blinker relays were combined into a single one for 1978-80 cars and was located behind the dash (somewhere below the tach or speedo). This “Flasher” relay now had 3 wires (light green/gray, light green/brown and green/light green).

If the behavoir of your flashes changes when other lights in the same cluster are switched on (i.e. side lights, brake lights etc) then 99.9% you have a bad earthing (ground) problem and/or a bad cell in your battery. To identify which cluster the earth fault is in, remove the other bulbs and then try it (i.e. if you removed the front side light bulb and the flash rate is then ok – that’s the one). You should sort this a.s.a.p. as it can cause other problems and is likely to get worse. It is probable that it is merely a corroded connection.

If the flashers don’t work properly both sides then the battery voltage may be low. The running voltage of a car is around 14v, the battery should be 12v. If the battery is in fact 12v then try a new flasher unit.

Upgrading to a modern elecronic flasher is easy. Most cars (e.g. Ford Escort/Fiesta/Sierra, Vauxhall Corsa/Vectra/Cavalier/Astra) use the same standard flasher which is almost a direct replacement for the thermal type relay – you just have to provide an extra earth lead.

Sample questions:
“My left directional flashes furiously,the indicater light only flashes once and goes out. I’ve eliminated the wiring to the directionals. I’ve ruled out from the steering column out and the flasher gets hot.”
The problem lies in the bulbs or earthing (grounding), the flasher units only work properly if they can read the correct voltage.

If you haven’t noticed, the Haynes manual’s wiring diagram is VERY wrong around this relay on US 1976 cars, probably other years also.
Visit the wiring diagrams page for excellent 75, 76 and 78+ diagrams