As technology gets upgraded every day, automotive manufacturers are paying more attention towards delivering a highly reliable product which performs its intended function throughout its useful life (without any failure). To develop a reliable product, accelerated combined stress testing should be conducted in addition to the conventional design validation protocol for the product. It brings out most of the potential failure modes of the product, so that necessary actions can be taken for the reliability improvement. This paper discusses about the field failure simulation and reliability estimation of automotive headlamp relays using accelerated combined stress testing. To analyze various field failure modes, performance and tear down analysis were carried out on the field failure samples. Field data (i.e. electrical, thermal and vibration signals) were acquired to evaluate normal use conditions. For accelerated combined stress testing, random samples were selected from various manufacturing plants. For each stress, design and destruction limits of relay samples were found using step stress approach. Accelerated test with different stress combinations were performed based on the analysis of field operating conditions and design limits of each stress. Failure modes as in field condition were simulated in the lab and failure causes were assessed. From the results of accelerated combined stress testing, reliability was estimated for the normal use conditions.