One of my best customers, Charlie Horn, dropped by my shop one afternoon and asked, "Why does my truck keep blowing the A/C fuse?" "Well Charlie," I said, "You've had this truck for six and half years, so you have to expect a few very minor problems. It's been fairly dependable." "I know," he said. "Still, Chevrolet® says their trucks are built 'like a rock'. Doesn't that mean they'll never break?" "Well, almost. There isn't a vehicle built that won't break down sometime," I replied. "Let's get your truck into the shop and find out what's causing the problem."

This conversation brought to mind a couple of valuable lessons.

First, Charlie was forgetting that my shop had always done the factory recommended scheduled maintenance on the truck throughout the years. That preventative maintenance was largely responsible for his truck's dependability. The second lesson was that I had been forgetting to advertise the fact that I have an ALLDATA® Automotive Information System in the shop, which supplies us with the maintenance schedules, technical service bulletins (TSBs) and accurate repair information.

So, what's the point for all technicians and shop owners? Make use of a comprehensive automotive information system. Don't forget to educate your customers about the value of preventative maintenance. And lastly -- advertise through newsletters, shop web sites and print ads -- what your shop specializes in and how you have the information to fix their vehicles right the first time. You owe it to your customers and potential customers.

Okay, who kicked my soapbox out from under me? I guess Charlie wants me to tell you how we fixed his truck's A/C problem. Well, here are the details of the TSB.

Some 1994 and earlier Chevrolet and GMC® C/K® truck owners may experience a blown fuse, erratic HVAC operation, or a blinking HVAC control head self diagnostic indicator. There are two possible hard to find causes that have been discovered.

The first possibility has to do with a six way I/P to HVAC connector terminal that may be shorting to the ashtray. The connector has slots to accommodate the terminal positive attachment locks that could allow metal-to-metal contact between the exposed terminals and the ashtray (Figure 1).

The second possibility is that the HVAC harness from the control head to the blower and mode door motors, running across the vehicle just under the dash panel, may chafe against the cassette deck support bracket (Figure 2).

Thanks to this TSB, repairing the problem is as easy as finding it. Both conditions can be corrected by taping or otherwise shielding the wires from contact with the respective metal edges. If the second condition has caused significant wire damage, make the appropriate wiring harness repairs.

Charlie's HVAC harness was rubbing against the cassette deck and intermittently shorting out the circuit. We spliced in new wire, taped the harness and insulated it to prevent future problems. Charlie's truck was diagnosed and repaired in record time and we both learned a valuable lesson.