I am getting multiple error messages and this unit fires up intermittently, but very infrequently. The latest code was "there is a problem with the inlet thermistor", so I popped out the thermistor and put my cheapo multitester to R-100 thru R-1 settings and didn't get a reading. The service manual states R = 2.47 K ohms. Do I need to get a multitester that reads R-1000? Could a bad thermistor be causing the 2 other error messages; "The blower is not getting up to speed" and , "The appears to be no gasflow..." ? Thanks!