The temp gauge of my recently acquired 91 EX (113K) is erratic. During highway speeds when it's moderately cold out it stays on cold even on long trips. As soon as I slow down or stop I will get a normal reading. The heater seems to be working ok (though not as hot as my other newer vehicles) so don't think it's the thermostat. Any others have this happen? Any suggestions? At this point I'm not thinking this is a big deal but am curious.

 

Do you have a manual or automatic? I have a 91 lx with a similar problem, the neutral switch seems to have some effect on the temp guage. In neutral or some other gears the temp is normal, but when I put it in first, it drops to cold. I haven't figured the problem out yet, but I guess it's not a big deal.

 

Mine is an automatic.

 

cooling fans? check with a/c off