Cage temps in the 70 degrees - what were the ambient room temps?
Where was the probe placed? Could it be hot there and not elsewhere in the cage? If the probe ws close to the heat source, it could give a false reading of hot while the actual cage was cold.
The test - plug your heat sources without any stat and what are the temps.
I'm NOT saying the stat was good but a thermostat can only do so much. A cold room will make it hard to regulate temps, as will a glass tank (you didn't mention enclosure type) Also probe placement is crucial and I believe it's not necessarily reccomended to power two differing heat sources with one stat.
>>OK... Heating elements...
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>>a) 20-30 gallon rated ReptiTherm UTH ( 20 watt approx)
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>>and
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>>b) a 75w infrared bulb in a equally rated reflective dome light pointed down at the basking site...
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>>What I was using to what I thought control these two devices was a Helix DBS-1000 which I had bought from a friend who was getting out of housing herps around 3 months ago. I tested it fully before putting any animals into the enclosure, it worked fine.
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>>I also had two probe thermometers inside the enclosure, one on the hot side, one on the cool side and was checking them periodically through out the day and the temps were normal for keeping BCI's... what wasn't normal however was the "bottom" dropping out of the device, allowing it to what I can only assume drop to a low enough tempurature to effect the snake. I had come home very late the other night... and I had left the enclosure set up to trouble shoot the problem, and found the cool and hot side temp to be 70 degrees at 2am. The drop I'm sure only compounded any under lying medical condition that snake may have had.. but I'm not 100% sure if he did have anything wrong with him medically... ( was acting like a healthy snake up until one week ago ) then he went down hill... took him in to get looked at... he died two days later...
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>>I did test the thermostat seperately after that night and did find it wasn't maintaining the set temps.
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>>Sorry for the length on this on there Jeremy...
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>>Karl
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Thanks,
Dave Colling

www.rainbows-r-us-reptiles.com
0.1 Wife (WC)
0.2 kids (CBB, selectively bred from good stock)
LOL, to many snakes to list, last count:
13.26 BRB
11.16 BCI
And those are only the breeders 
lots.lots.lots feeder mice and rats 