When curing sausage, which is more important temperature or humidity?

You ned to get your hands on a computer fan (they are designed to run 24hrs a day). I simply mounted one of these inside wall of my curing chamber (down low - as wet air drops), cut a hole in the wall of the fridge with a hole saw - which allows the fan to exhaust the moist air from within the curing chamber. I also cut a similar sized hole at the top of the curing chamber on the opposite side which allows dry air to enter the chamber as the wet air is exhausted. I have it rigged up to a cheap humidity controller I purchased off ebay, so when the controller detects high humidity (whatever you set it at), it exhausts the humid air.

I am using a frost-free freezer (large) and at the moment am drying 7kg. I have a temp controller which works perfectly, but as the weather changes I get a lot of variation. A humidistat controls a humidifier, so have no trouble in keeping the humidity up, which I like to in the early stages.

The problem arises overnight when the ambient temp is lower than the fridge and so it doesn't cycle. To combat this I have a heat bulb in the bottom which lifts the internal temp and causes the fridge to cycle, thus removing moisture. The heat bulb and the humidifier seem to fight each other but according to the gauges, gives the correct environment.

Have not had any mould problems or failures yet - hope this helps.

Too humid an environment will, as you are seeing, slow the curing process down. As long as they are still decreasing in weight you should be OK but you need to be careful of moisture forming on the outside of the casings as this may encourage nastier moulds to grow beyond the white one expected on salami.

If they are not losing weight at all this is a problem as this indicates the water content within the sausage is not decreasing and a high water content will encourage bacteria growth and eventually spoil the meat.

Try opening up the refrigerator you are using for a few hours a day to let the moisture out (the trade off is that you will heat it up a bit but if it's only for a few hours you should be OK). If a more severe drop in humidity is needed then aim a desk fan at them and run it for an hour or so a day. Circulating the air around the sausages will help remove the moisture but may not be all that economical when you consider the electricity bill.

EDIT:

If opening the fridge and/or using a fan don't work for you a more radical approach that might work could be to try Silica Gel packs (like the ones you get in electronics packaging) in the bottom of the fridge. This is a totally untested idea but theoretically should work as they are designed to absorb moisture and are non-toxic (although the label warns against eating them it's more a choking hazard than any poison to worry about). I'd be very interested to hear how successful you are if you try this route.

I have a vent in my curing chamber that's an old refrigerator converted over.I used a metal dryer vent and caulked the perimeter once installed, i also leave the metal flap open a bit with a magnet. This allows circulation of air inside of the chamber via the fan. I have a steady 58 degrees with 70% RH.

The short answer is within the ranges you describe, humidity is more important than temperature. Reasonable temperature fluctuations will have little effect, because you've already created an environment hostile (hostile, not impervious) to harmful organisms. "Spoilage" is cause by bacterial action. If bacteria and other organisms cannot survive, multiply, and act, then you're not at risk of spoilage. This is why canned goods never go bad. On the other hand, if the humidity is too LOW, you're at risk for case hardening; the formation of a dried layer containing a raw center. This is bad, and dangerous. Theoretically, if the humidity outside the sausage is any amount lower than inside, you'll have drying action, which is good. The purpose of humidity ranges is to ensure that you have consistent drying and moisture loss throughout the drying process. Keep some air movement, do your best on temp, and dial in your humidity, and you'll be fine. Good luck!

You should see if Amazon or local retailer don't carry small dehumidifiers that you can put in your makeshift fridge. I have seen people use them in there wine fridges which the use as a cheese fridge.