I had one that wouldn't inflate (stuck closed) when it was cold. I could aim a heat gun at it and it would start working. I replaced it and the new one worked fine. I took it apart to see if I could see what went wrong, fix it and have a spare. It is filled with a mineral oil-like fluid, reed looking things. I closed it back up and threw it away.
I called Freightliner, got the part number and bought it online on one of the discount semi truck parts companies.
My Kharma ran over my Dogma.