We use Ofna Fail safes and recommend them to all our customers, you can get one on Ebay for anywhere from 10 to 25 Dollars, just have to look, They are very reliable I have had mine for about 2 years and still works great. Yes the spit test is a pretty good way to see what's going on with out buying a temp gun, You can get the temp guns off Ebay for cheap too. They Work pretty good I bought one but don't use it, spit test and blue smoke has worked good for the last 20 years so I just stick with it.