Thought this was a great post by u/Reeces_Pieces over on Reddit, so I decided to bring it here:
Title:
Hopper was stuck on Red/Blue flashing (Sensor Damage) Lights. here's how I fixed it
*UPDATE: looks like the post has been deleted for some reason*
https://m.reddit.com/r/GrassHopperVape/comments/4tyxi9/hopper_was_stuck_on_redblue_flashing_sensor/
Summary: Full clean of backend threads and the gap below the temp control brought hopper back from the red/blue (or was it blue/red, meh) lights of death.
I found that very interesting, especially the part about the temp dial. Thanks for posting it.
My backend has slowly been getting warmer the past week or two. It's more noticeable on one of my two batteries. It's not "hot" yet, so I didn't think it was broken and figured I'd wait till I get my preorder if I chose to do anything about it.
I had a half used chamber in my Grasshopper while I was reading that post, so I didn't want to mess with iso obviously.
I decided to just try moving the temp dial back and forth as mentioned in the Reddit post you quoted. I held the clip with one hand and rotated the temp dial very fast between minimum and maximum. The movement smoothed out while I did this. I probably did that for 5-10 seconds, and then set it back to 4, my usual temp setting.
I was amazed to find that the backend is no longer getting warm. On my "bad" battery it does get a tiny bit warm, but it's barely perceptible. On the good battery it is as cool as a room temperature Grasshopper.
My guess is there was some lint or dust or grease in there. It looked clean but due to the nature of the hopper's electrical connections even a tiny speck of dust could potentially cause issues. I use the leather sleeve which leaves the dial exposed, and I also always recharge externally, so I unscrew the backend a lot. A little maintenance is to be expected, but it was way easier to fix than I expected.
It could be a coincidence but it's worth a try at least for anyone with a hot backend. I should note that my backend never felt hot enough to burn me, but it was gradually getting warmer as the days went by.