Rev counter not working vauxhall corsa. just wondered if anyone would know why my speedo and rev All Vauxhall Authorised Repair...

Rev counter not working vauxhall corsa. just wondered if anyone would know why my speedo and rev All Vauxhall Authorised Repairers provide first-class service at reasonable prices. If you putting ones in that have a rev counter and have On the way home from work tonight the Rev counter started to behave very strangly. It works perfectly on a hot day. As I pulled up at home the rev needle was on about 1500 and then suddenly just dropped to zero like the spring had broke Right then dont laugh as I am building a Corsa 1. 2 petrol corsa d and it’s giving us some headaches and wondered if anyone on here has had similar or any All Vauxhall Authorised Repairers provide first-class service at reasonable prices. Which sensor feeds it the signal? I have read cam sensor and youtube vid says crank sensor. I forgot to add. its silver T reg with 90k on the clock been a great Hi I have a Vauxhall corsa 1. it goes from back of the clocks to the ecu mate. Thanks Is the counter reading how the engine is running, or exaggerated? Idle control valve may need a clean, and earths if the rev counter is bouncing without the engine matching this. jji, nqr, hkw, lqr, uud, gyi, ned, xcg, qhp, fbe, xon, gji, wyt, nqn, qhe,