Cant get temp right

[clowngrl]

I built an incubator out of a styrofoam box, followed miss Prissy's directions. On one of the short sides I have the light on one side, the fan in the middle and then the thermostat. There is a sealed jar of water at the other end of the bator and a small bowl of water in the middle. I added 4 vent holes on the long sides.
I have 2 digital thermometers, one with a probe for internal temp and one for air temp and humidity. I couldn't find a water wiggler so I filled an egg with hair gel put the probe in and sealed it.
I read that the internal temp would change slower than the air but the probe one changes just as fast as the air temp. When I open the lid the internal one starts dropping within about 30 seconds.
The real problem is that no matter how I adjust or move the thermostat I cant get it to a small temp range. I can get it to 99.5 but it goes down to 94-95 and up to 101-102.
Here are the things I tried and none of them made much of a difference. First I put the thermostat on the side with space behind it for air, then I read about it reading the temp of metal so I put a metal plate behind it still with a gap for air, then put it up against the metal plate, then put it laying down on the bottom on and off the metal plate.
What am I doing wrong? How do I fix it?
Thank you

 

[mulia24]

why don't you not try to put the bator at *stable* place, mean that there's no shake or sun light or wind that could affect the bator, then pull out the thermostat, then, try to change bulb till the bulb create a stable temp? i mean find out the right bulb that can produce right temp.

there will be any fluctuation, yes indeed that's normal, but it will make it more easier than try to find out the best set of thermostat.

 

[Eggcellent]

What kind of thermostat are you using? You may need to get one that doesn't allow such big temp swings.