I have a water dispenser in my fridge that keeps freezing.
Obviously I know nothing about your fridge, but the first thing that comes to mind is, are you running the fridge too cool?
What is the air temperature in the fridge?
Can you turn up the thermostat a couple of degrees?
I ordered a heating element for the door because of the defect but I read online that will even fail.
It is not clear to me what you are saying here.
Is there an existing heating element which is faulty, hence the freezing water dispenser?
Or, this is an idea of yours to add a heating element to fix the icing problem?
Why does the online world think that it will fail? Did they say?
The quick and dirty idea is to fashion a copper wire to stick up there and quickly thaw the tiny blockage.
I like quick and dirty!
taking a 9v battery or something to heat an element to anywhere from 70-90F
Woh, hold on there. That is a recipe for failure.
If you mean the little 9v radio battery, that is not a good choice.
They cannot provide much current and not much energy (ie what current they can provide will not last long.
If you are going down this route you need a bigger battery. If I were doing this, I would think about using a couple of "C" size cells.
Now, what to use for a heating element? I am at a bit of a loss to know what to suggest, but no doubt that someone here will have an idea or two.
As I have been sitting here typing, the thought occurred that (and I am not suggesting this as a practical solution) a "Wahl IsoTip" cordless soldering iron would be a starting point.
Looks_Like_This
Practical difficulties:
The tip would not reach 3 to 4 inches up the tube.
The tip would melt a plastic tube in no time.
So with those insomniac ramblings, I will go away and look at something else.
JimB