Abstract: A resistance weld control employing a model-based run-to-run estimate of load impedance, giving the weld control system the ability to maintain and predict the expected impedance of a successfully completed resistance spot weld, and to detect when the load impedance observed by the resistance weld control is within a target neighborhood of that impedance predicted by the model-based run-to-run estimate of load impedance. A target weld current and a range of weld times may be specified, such that the actual weld time employed in making the resistance spot weld is responsive to the time required to complete the contact preparation phase. Further, a fixed weld time and a range of target weld currents may be specified to make a resistance spot weld, such that the actual target weld current employed is responsive to the time required to complete the contact preparation phase of the weld.