John Shriver , Jan 09, 2010; 09:42 p.m.
Have a look at this page , which has the National Camera service manual for the K1000. Sounds like there's a problem with the resistor that reads out the sum of shutter speed and film speed. You could be lucky, and someone assembled it wrong, "out of sync". You could be unlucky, and that resistor is worn out or broken. I doubt Pentax still sells spare parts for the K1000.
Good affordable repair service at http:/www.pentaxs.com. But another K1000 might be cheaper than repairs, they are common, although the "camera course" phenomenon causes them to fetch a somewhat inflated price. (An MX, KX, or K2 are really better cameras, and often cheaper. But the K1000 is a nice camera.)