Where does the RPM signal come from

Hamster · Aug 27, 2009

I have a friend coming over from Holland in a couple of weeks as he's touring the UK to watch the 1 day cricket. While he's here we're doing a cambelt change but he also has a problem, his rev counter doesnt work.

He's tested the gauges and they are ok but theres no signal coming in.

Basically i'm looking to find out where the Rev counter feed comes from? I've searched numerous threads but cant find a definitive answer.

Any pics of where to connect to would be super useful, i'm not great with reading diagrams.

stoker100 · Aug 27, 2009

comes from the 3 pin connector on the disty, goes through a 1k resistor to the tach IIRC

Hamster · Aug 28, 2009

see this is the thing

now i've heard it comes from the coil, alternator AND dizzy.

Anyone clear this up for me?

stoker100 · Aug 28, 2009

alternator = no way

the coil is in the disty so its one and the same thing really. technically (now someone correct me if im wrong) the tach input is connected to the middle pin of the 3 pin connector, this pin goes DIRECTLY to the tach input AFAIK, on the disty side it goes through a 1k ohm resistor which connects to pin 1 of the 3 pin disty connector. hope that helps.

Hamster · Aug 28, 2009

wonder whats causing the loss in signal then? The resistor?

stoker100 · Aug 28, 2009

possibly, but the signal that goes to the tach probably also goes to the ECU (again correct me someone if im wrong) so if the ECU can see the rpm then it must be between the dash and the ECU, firstly i would probe from the middle of the 3 pin connector to the back of the cluster (one of the 2 long connections) there should be continuity (a short) to one of the pins, if there is then the issue must be within the cluster.

Where does the RPM signal come from

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