I have a Nashbar floor pump with an automatic Presta/Schrader head. The valve holes are on one side of the head and the air is supposed to switch to the hole with the valve inserted. It used to work great but now it won't switch, i.e. it blows air to the side that's not attached.
I tried the normal stuff, banging, wiggling the head etc. Is it dirt inside the head? Worn parts? Has anyone tried to take one of these apart? WD40? Or should I just get a new pump? It works great otherwise; when it's selected to the right hole (sometimes Schrader, sometimes Presta), but 90% of the time it's on the side I don't want! And because of my budget it was one of my "major" purchases!