If you had an alternator failure or some type of electrical failure you might want to shed non-essential loads. You might want to be able to manually switch these fans off in such a situation.A seemingly trivial question: Like many, I am installing computer type fans in the glare shield. My question is whether to wire them to a separate switch or just run them through the avionics master. In other words, is there ever a time when you would want them off?
Actually a better solution to the problem is this:My question is, do you even need these fans?
Many RV's are flying without them.
If you are worried, cut some nice looking vent holes in the top of the glair shield and let the heat rise on its own.
(Why add the weight and complexity?)
Actually a better solution to the problem is this:
http://vansaircraft.com/cgi-bin/store.cgi?ident=1442822538-132-612&browse=heatvent&product=air-routing-devices
Weight penalty = 'little to none'
Complexity of installation = 'dirt simple'
Power demand = 0
reliability = 100%
I can testify these have been working flawlessly for me for the past 5 years now.
No, I do not fly in rain. I had my dual EFIS screens going black on a handful of occasions early on in my flying before these were installed. I installed these air diverters and have had no issues since. I can, however, see where if you did fly through rain on a regular basis this could be an issue but for VFR conditions you cannot beat the simplicity and low maintenance of this as a solution for getting cooling air to the electronics behind the panel.Steve, do you fly in the rain? Back in the 70's Cessna used something similar. What they got was rusted and corodded avionics, and a SB to disconnect direct outside air cooling.
It's well known that heat is not good for electronics, but how much or where the threshold is is hard to say. I figure a couple of computer fans are cheap insurance. Mine are not switched but do run thru a pullable CB for emergency shutdown.
...A automatic thermal switch might be the ans.