Take it to a trusted garage and have them run a set of diagnostics on it. There may be more wrong that a malfunctioning EGR (exhaust gas recirculator). Additional Information: An exhaust gas recirculator is a device that admits a controlled amount of exhaust gas back into the intake manifold. Sounds crazy, huh. This thingy was added to reduce the formation of nitrous oxide becasue the engineers couldn't think of any other way to do this at the time while remaining under the then current design retraints. It was recognized that it was going to be a problematic device since it is a valve that must handle hot exhaust gas right out of the cylinders. Issues are high heat and fouling by exhaust particles. Nitrous oxide is formed in the combustion process by temperature and pressure: The higher the pressure and temperature, the more nitrous oxide is formed. Admitting aome exhasut gas into the mixture casues it to burn at a lower temperature and lesses the pressure as well, but you know, this also lessens engine efficiency and power, so is it a good thing - maybe. That's the rub: as the fuel mix is adjusted toward best efficiency, nitrous oxide also rises. The EGR is supposed to meter exhaust gas into the intake under specific conditions. There is none at idle and varing amounts at other times. By adding the EGR, it was found that the spark timing could be advanced toward the same settings that were in use befoe the advent of polution controls. On some engines, a knock will occur if there is no EGR function under this set of conditions: Engine fully warmed up; part throttle while at a moderate speed, say 35mph; then encounter a small rise in the road surface that requires slightly more throttle opening to maintain speed. There is another source that makes a sharp, almost clicking sound, and that is a blown exahust gasket. When the leak is small, it may be quiet at idle and low power output, but will let itself be heard as soon as more power is called for. This sound is distinctive and sounds quite different to a knock or valve click. What's fuel knock anyway? An internal combuation engine runs the best when the fuel burns evenly and casues the pressure to rise in a smooth manner. Knock occurs when nearly all of the fuel explodes at once producing a sharp, explosive pressure shock instead of a smooth 'push'. Many hours and much money has gone into knock research, and still does today. Its a difficult thing to quantify since the process takes place inside the closed chamber above the piston. How does one get a look inside the combustion chamber? And how does one get a good picture through the flame? One of these tools is a special sparkplug that is fitted with a pressure sensor that is built to withstand the rigors of the combustion chamber.

Mine is Suntouch, too. I'm still getting used to the sound. It used to wake me up a lot (adjacent room),but I no longer hear it all night. I wasn't expecting it, though.

I have a XL19 unit making a clicking noise emitting from the defroster board CNT04335, and the red led is flashing twice per second. The unit had leaked freon, located and repaired yesterday. Recharged system with 17 pounds as noted on panel, with good pressures. Noticed compressor unit was cycling more then normal along with the clicking and led flash. Bad defroster board?

The coefficient of expansion is different for each size of pipe, but for illustration let us consider 3/4" CPVC. For 3/4" CPVC the expansion is 1" per 100' of pipe for every 1degF of temperature change. Assuming the pipe begins at an ambient temp of 70 degress when you start your shower and the hot water is set for the code max of 125 degF the temperature differential in the pipe would be 125-70 = 55degF. The thermal expansion would then be 55" per 100ft of pipe. We rarely see a run of pipe longer than 50' in a residential system, but even at 50ft the thermal expansion would be 27.5". The CPVC installation handbook suggests a 18" expansion loop at every 30' on a straight run and the loop should be located near the center of the run. To make the expansion loop the pipe is cut and a 90deg elbow is installed. The line is then stubbed out 18" and a 90deg elbow is installed. A short 4 to 6" length of tubing to another 90deg elbow turning back towards the original pipe and then connect the loop to the original pipe with another 90deg elbow. On the ends where the pipe drops down through holes the pipe should be run about 18" to one side of the hole with an 18" offset from the pipe to the hole. IN this manner as the pipe expands the 18" horizontal offsets can flex slightly to absorb the expansion. Insulating the pipe will not prevent the expansion because the temperature differential results from the temp of the liquid in the pipe, however if the pipe is first insulated, then pipe hangers large enough to fit the exterior of the pipe insulation are installed, the pipe is free to move slightly within the insulation. If you have your water lines run through the attic space you definitely want the cold water lines insulated, otherwise as the pipe cools from the cold water moisture will condensate on the pipe and drip down on your ceiling causing water damage the same as a leak.