When the problem you're trying to fix isn't obvious, it can help to have a flowchart that logically takes you through the process of elimination. Several of my published computer repair books feature a troubleshooting approach based on flowcharts. I've been working on a new series of automotive diagnostic flowcharts, with drafts completed for starting problems, overheating and coolant loss, and ticking noises. Click on the miniature troubleshooting flowcharts to expand for the full size, with expanded text explanations for every decision point.
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