I've had a long,ongoing thread with the Volvo Forum on this problem. Cruise control in my 1990 240 wagon quit. To avoid details: I've run all the tests in the shop manual for this model. All circuits seem to be working. I replaced the module (used, I'm assuming it works). At some point, the red/white wire was attached to the extra post on the speedometer speed sensor. But. . . a test of frequency along the yellow wire shows increase of frequency with increase of speed. I can buy a insturment cluster with a supposedly working speed censor, but hate to get into "parts replacement" without some indication of a problem. In this case, all seems to be working, except, of course, the cruise control. Any ideas.