Volvo Repair: 1992 and 1993 speedo/odom/trip meter...., other vehicles, trip meter

Question
Our speedometer/odometer on our 92 740 wagon (265,000 miles) started bouncing around and sometimes quitting after working and temporarily coming back to life after not working before failing completely. Then the horn would work sporatically. Then the fan quit but the heater keeps putting out heat even in the off position. One time the fan suddenly started working for one day but hasn't worked since. Are these problems related?
Two months ago we bought a 1993 850T wagon with 160,000 miles and now the speedo quit working on that too!
I just discovered this awesome site and have been reading about speedo problems. Do we need to replace the speedohead on both cars? Hubby hasn't worked on Volvo's but was able to fix most car problems for past 20 years on our other vehicles.
We'd appreciate any advice.
Thank you!
Melissa

Answer
  Melissa, the 740 head needs repair, not replacement. I'm sure your husband can remove it, box it and ship it to a repair facility. When you hit the trip reset while in motion, it's hard on the little plastic gears. Usually @ $ 90-110.00 to have repaired.
   Does the 850 have the odometer display on an LCD (digitally))? Not the roll over numerals like the 740?

Mark