heater box under bonnet has a small oblong cover size of 20 cig packet lever it off carefully and the resister is secured with two screws it has three coils and a multi plug all of which rust, melt and generally cock up. if this is damaged then your speeds will fook up. the one on my escos melted and i could smell it in the car, even the wiring had started to overheat there was a full thread on this a while a go try doing a search