Harbor Freight over here too.
Mine worked for a while but the readings did seem a little low. Then again 90-110 psi might not be too horrible for 30-40 year old bikes.
Then the little rubber ring at the end got all chewed up and it doesn't hold its reading.
They will give me a new one though. I just have to remember to take it next time I go.
Thats the thing about harbor freight. Most of their stuff is pretty crappy, but they have always just given me a new thing every time something of theirs breaks. Power tool, hand tool, whatever. No receipt.
I think it might be because I am in there all the time, but it might be a policy or something.
God, they have replaced so much shit I have broken.
About 7 screw drivers (pry bars, ice chippers, impact screwdrivers, chisels, whatever I need to use them for.)
2 strap wrenchs
A rotary tool
A compression tester soon.
More I can't remember. Half the time I walk in there the girls are like oh god what did you break this time?