We examine the experimental pressure response for a set of electrorheological valves operating at several steady flow rates to step function voltage inputs and analyse the factors that may contribute to the complex forms observed. Using a numerical algorithm incorporating a viscoelastic model for the fluid the response of the valve flow profile to changes in theology is found to be relatively fast compared to the experimental pressure response and thought not to feature as a significant contribution to the final shape. The dynamic interaction of the valve and its associated system of pump and connecting pipes is investigated using a multi-element lumped parameter model and reveals a frequency spectrum containing resonances comparable to the experimental results. A simple lumped parameter model is less successful. Using the multi-element model for the system an upper bound can be placed on the basic response time of the electro-stress itself under realistic engineering conditions.