Originally Posted by Silver pied
What is the problem that occurs with the wafer switch incubators.
Those older-style wafer switch incubators have two big problems. First, they don't "know" how hot or cold they are running, they don't "hold" a set temperature using a thermometer to check themselves -- it's more a relative temperature, so they tend to drift and not stay really stable. Second, the wafer switches tend to fail easily and often, and may become more unstable with time. Sometimes the response to the controls is weird and not linear.
I've hatched with them, but it's harder. My hatches improved when I added thermal mass to help stabilize the temps and used 3 or 4 thermometers to monitor. And sat by the incubator and babysat it, and made sure the room temperature stayed as constant as I could -- no easy thing if you don't have perfect HVAC in the room with the bator. Adding clean, disinfected rocks increased the thermal mass and stabilized temps somewhat. I tried adding a fan, but it didn't help as much as I thought it would.
Switching to a digital temperature controlled incubator helped me a lot, and adding an automatic egg turner (in addition to continued manual turning twice a day) also helped dramatically.
It's not impossible to hatch with a wafer switch incubator, but it can be frustrating and difficult. Some folks do fine. Experience helps.