Help! Area chart is showing my data wrong!

I'm trying to create one area chart that is the combination of these two graphs. The data sets are one that is all positive numbers and the other is all negative numbers. This is the area charts individually:
chart1.jpg
However when I try to highlight both data sets and say build a single area chart I get this which clearly is it adding and subtracting the numbers from themselves:
chart2.jpg

What is really unusual is that if I switch this to column chart, then it works fine and the data looks as it should in column format which is hard to read.

chart3.jpg


And if you are wondering what the data looks like, here is both of the tables:
chart4.jpg

So can anyone help me to make one chart of data that is not being merged together but to remain as in the initial two graphs?

Any help would be really really appreciated
Thanks
David

Thank you! I will try that