Hello,
I am trying to simualte the below circuit. The simulation runs fine, and I could plot all the signals. But when I tried to change some parameters, I got this error:
Error: vector V(Net-Q1-Pad2) not found!
I’d try making it all lower case…
Dunno what you mean by “simulation runs fine”.
The positive voltage source terminals are connected to input labels. Input labels are connected to input labels.
Please don’t do that. Global labels are NOT intended for this use.
Remove the labels and draw connections as needed (you know, lines/wires).
At the end, you’ll find that Q1 has no Spice model. You’ll need to find one on the web.
Looking over the post, it seems a bit scolding… that’s NOT my intention, just my style. I’m trying to help here.
Have fun. 
Here’s your circuit in two (corrected) versions, depending on your taste.
If the IRF540 Spice model is added to Q1, there’s a good chance it will simulate as expected:
Thanks for your help.
I’ve changed the labels and now everything is working fine.
Concerning the spice model, i am aware that I need it and I provided it, but usually the problem is where to find them.