Water Heater Woes

Last week our pilot light went out. When we tried to relight, the pilot would light but when I released the button it would not stay lit, so I could not start the furnace of course.
A friend replaced the Thermal Couple for us and that seemed to fix it. The pilot would stay lit in "pilot mode" then we could replace the cover and start the heater as normal. We set it to the mid-way mark (labeled "Hot"). Later that night, it went out again but we were easily able to relight it. No problems since then until today, been about 5 days.
The furnace is in an outside room off of our carport and it gets very cold in there (uninsulated) so we put some insulation in today. We used a water heater blanket, but only wrapped the top 3/4 of the heater in order to avoid touching the control box or getting anywhere near the pilot area. When doing this, the pilot went out so we turned off all the gas, just to make sure we didn't have any problems. After we were done, we relit the heater.
This time, the pilot worked fine but when I put the gas control knob into the "full" position and then used the Temp dial to get the furnace to light, rather than catching at the lower temp area (several lines under "hot"), it wouldn't catch until 1/2 way between "hot" and the max setting. Now, if we try to set it down midway to "hot", which is the recommended setting, the heater doesn't stay lit, although the pilot does. So, we took off all the insulation, checked to make sure the thermal couple wasn't loose or damaged and can't find anythign wrong, but we cannot set the furnace lower than 1/2 way between "hot" and max. This troubles me because last week when we replaced the couple, it could be set a lot lower if we wanted.
The furnace was made in 1996. We bought the house in June '02 and have had no problems, outside of the hot water not lasting as long in the winter as in the warmer months. But since we're in Arkansas, we don't have much cold weather, so it's not been a huge bother.
Any advice? Should we call out a plumber to look at it? Is it okay that it doesn't catch until this setting?
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julie hicks wrote:

That sounds like the calibration of the thermostat (inside the gas control unit) has drifted. They are very fussy and can be shifted by some physical disturbance, like force applied to the gas pipe.
As long as it turns on and off and keeps the water temp where you want it, I wouldn't be concerned about what the dial reads. Jim
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snipped-for-privacy@hotmail.com (julie hicks) wrote in message

ok so i'm an idiot! :P of course it wouldn't "catch" until i get it to the hotter settings because the water in the heater right now is already hot, so unless i set the temp to hotter than the water temp is currently, only the pilot would stay lit, right? the reason it would catch at the low setting last week was b/c the water was cold inside the tank. only took me a few hours to figure that one out! LOL
i think the pilot tip is dirty though. from what i've read, the pilot probably went out the first night and earlier today when the main light kicked on or off, it was blown out by the force, so i will clean it when i put the insulation back up.
sorry to bother everyone! :)
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