its the black box located on the driver side front fender/wheelwell. If you take it apart there is a strip-type fuse on the top of it that can burn through if you wire it up wrong, or just from old age sometimes. You should be able to trace the glow plug wires back to the relay box.

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TC
Current stable:
- 2004 Mazda RALLYWANKEL
- 2007 Saturn sky redline
- 2004 Explorer...under surgery.

Past: 135i, GTI, 300E, 300SD, 300SD, Stealth