Engine fan on and off every 15 seconds at idle, and under 30 mph.

[Mr Hagg]

When we have any questions about the fan coming on I hook up to insite and see whats comanding fan on and off. At that point I know what to do to fix problem. The most common problem is the high pressure switch on the ac. It will get loose terminals and as the engine vibrates it will cause it to loose connection. We normally tighten the pins up in the connector with a small pick. I have seen a few cases where the wire was broke at the end of the pig tail from where it was tie strapped over but rare. But really need to hook it up to know for sure,,,