Incubator temperature-will they hatch?

I have 2 incubator and I'm having a pretty hard time keeping the temperature stable. I have 9 hen eggs in lockdown right now after setting 36 eggs and the temp went up to 40C/104F so there were a lot of early deaths. This was in my Hovabator still air bator which is the first time ive used it. The 9 eggs are in my small bator now, a really old brinsea octagon forced air. But I candled them today since 2 should have hatched by now and the others should be hatching today or tomorrow but i cant see movement in any of them and a few of them still have a lot of light orange fluid in them. I candled them 2 days ago and 2 were ready to internally pip but theres no movement today When i first put the eggs in this bator for lockdown the temp was right then it dropped down and i had to turn it up but it went up to 39C and was still going up so i turned it down again and its sitting at 34-35C and i dont know what to do

I now have 10 runner eggs (1 hatching next week, 9 in 3 1/2 weeks) and 24 hen eggs in my still air and the temperatures all over the place but i think i might have settled it at 38C now but when i open it to candle the temp drops and dosnt come back up so i have to adjust the knob again.

Could someone help me on keeping the temp stable and whether you think these eggs are going to hatch especially the ones in lockdown ?
thank you for any help!

All I can say about the Hova Bator is they usually hold great temperature. Your temp will go down in incubator when lid is opened but the egg temp will stay steady. Leave the thermostat alone and trust it will return to the previous temperature. On another note some people have problems with very sensitive thermometers. Ones that change fast, will cause distress as it reads the high and low of the incubator as it swings back and forth 2 C turning on and off. Keep in mind that's just the air temp in there and your internal egg temperature will be the average of the swing.

If your incubator temperature swing is way out then add a heat sink, put in a few bottles of water or stones to hold temperature steady. When incubating with a dozen or less eggs you could use extra heat holding mass in there to keep the temp stable. When incubators are full of eggs you wont see that kind of variance, compensate with stones or bottles of water.

i agree with egghead... all I could add is that hopefully you dont have it in a spot where the sun hits it part of the day or near a heating or cooling vent. If you do, you need to move it to a place out of the sun that stays a constant temp. I know a lot of people will use a closet as it is not subject to a lot of temp fluctuation

Thank you for your help , I will put some stones in the small incubator but i think i might have to try and turn it up a bit again cause its still at 35C. After that i will leave the temps alone and hope the eggs are still ok

Well i put stones in yesterday adn didnt touch the temperaature at all and a couple of hours later it had gone up to 36C. This morning i got up and it had gone right up to 40C again! So ive turned it down but im going to move the eggs back into the Hovabotor and lie them beside the turner if they even stand the slightest chance of hatching now! I just dont see what the problem is this time, ive used that incubator so many times and never had a problem with temperature. Maybe its just getting old?

reading some of these stories I often wonder if some DIY Bators are better than Store brought. some of them anyway. Then, I wonder if you get a cheap store brought bator and modify or upgrade the element, fans and thermostats to better ones, or even build in secondary sensors as redundency. maybe.

Um, just a question for more information. Are you using the built-in thermometer on the incubator?