I am on my second Northern Tool $40 helmet. After about 10 or 12 years the first one gave up the ghost so I bought the same one to replace it. I took the cartridge out of the bad one and just left a clear lens so now I have a good shield for grinding or ????
If the replacement module is the really high priced one you can shop around and find a complete auto dimming helmet (3 or 4 helmets for less price of a replacement module) for less than the price of a module.
I've had couple of the high priced helmet's that the module quit dimming and the internal battery was bad. I was able to replace the battery on one of the modules after gently taking it apart.
The other one (which was a expensive helmet) I could not find a replacement module battery, but rigged a cordless phone battery (of proper voltage) inside the helmet with the wires extended to inside the module.
A hint that it's the battery going out is sometimes you can place the helmet outside in sunlight and after awhile it will auto dim for little while.
Light is what charges the module battery such as sunlight or welding flashes.
Like the one guy says they make a good safety grinding hood if you can just leave the clear lenses installed.