Fermentation temp. control
Lost temperature control during fermentation, I can get the fermenter to temp. but cannot control during fermentation. Can I still make beer?
You can ferment, but the temperature is likely to go up to say 25 to 27 deg C instead of a target of 21. So it is likely to taste quite different, and you will probably have somewhat less CO2 left in solution. The fermentation will be faster, with probably a lower pH, and if you are using a top cropping yeast, then you may well not get a yeast crop, because it sinks so rapidly. You stand a chance of getting more yeast autolysis. The yeast may not repitch so well.
Having said that, I know of a few brewers who are also unable to control, and simply let rip. But I have also worked extensively with manual control of the cooling.
Assuming you still have some sort of coolant available, and have simply lost the auto control, then there is little problem. A little less accurate control, but control is still possible.
You simply have to check the temperatures on a regular basis, say no more than eight hours apart, and just let a little cooling take place. If you can cool for a few minutes at a time, then check the temperature say 30 minutes after turning off. Repeat if necessary. You are probably better keeping a degree warmer than usual than a degree colder to prevent the fermentation stalling, particularly once the gravity gets below 20 SG.