The second thing to check is the temperature of the system. When the system is working properly, its temperature can sit anywhere between 40 & 120 (degrees Centigrade). If you have TWO gauges, one should always read higher than the other.

When the temperature shown on the gauge (or gauges) is the ambient temperature (i.e. the temperature of the space in which it's located) then it needs attention. Time to call someone to fix it.