diff --git a/README.md b/README.md
index d5b0fb9..507381e 100644
--- a/README.md
+++ b/README.md
@@ -149,23 +149,29 @@
   remains displayed), it means that something is wrong with the
   temperature measurement hardware.
 
+* If the timer detects an error reading the probe - for example, if
+  the probe is defective or the wiring is compromised - the
+  temperature display will blink 998F to let you know.  If you are in
+  a film or paper correction profile, the timer will also sound an
+  audible alert (see below) to remind you that it cannot correct for
+  temperature. Both the blinking and the audible alerting take place
+  whether the timer is actually running or not.  This is intentional
+  to make you take action.
+
+
 * Pressing the momentary contact footswith start/resets the timer.
 
 * The SPDT switch selects Film correction, Paper correction, or
   realtime (no correction).  You can change this while the timer
   runs.
 
-* When the film profile is selected, the displays are dimmed on the
-  assumption that film is panchromatic (it can "see" red) and far more
-  sensitive to light than paper.
-
 * If you are in a film or paper correction profile, and the
   temperature is beyond the range of the timer to correct, the
   temperature display will blink.  This lets you know the timer is not
   capable of correcting for temperatures in that range.  This does
   not happen in the realtime profile.  There is also an audible
   alert (see below.)  Both the blinking and the audible alerting
-  take place whether the timer is actually running- or not.  This
+  take place whether the timer is actually running or not.  This
   is intentional to make you take action.  If you want to
   do compensating timing, you have to get the temperature back
   in range.  If not - say, you just want to measure temperature -
@@ -185,6 +191,9 @@
   is beyond the range of the timer to correct, you will hear
   5 short beeps repeated.
 
+* In film or paper correction profiles, if the temperature cannot be
+  read from the probe, you will hear 5 short beeps repeated.
+
 ## Calibration And Tuning
 
 The timer should pretty much be ready to run "out of the box".  But,
diff --git a/devtimer.py b/devtimer.py
index ab46cab..b65e5b2 100755
--- a/devtimer.py
+++ b/devtimer.py
@@ -1,7 +1,7 @@
 #!/usr/bin/env python3
 # devtimer.py - Temperature Controlled Photographic Darkroom Timer
 # Targeted for RaspberryPi
-# Copyright (c) 2018-2021 TundraWare Inc.
+# Copyright (c) 2018-2023 TundraWare Inc.
 # Permission Hereby Granted For Unrestricted Personal Or Commercial Use
 # Code Repo Here: https://gitbucket.tundraware.com/tundra/devtimer
 
@@ -57,6 +57,11 @@
 DEBOUNCE_TIME = 1.5         # In seconds
 MINUS = 16                  # Index of minus segment table lookup
 
+# Error Codes
+
+PROBEERR = 998              # Indicates probe read error
+SENTINEL = 999              # Initial temp display
+
 # Range of compensated timing
 
 TEMP_LOW=55
@@ -136,12 +141,14 @@
 def monitor_temps():
 
     while True:
+        try:
+            probe = open("/opt/devtimer/temp_probe/w1_slave")
+            temp = float(probe.readlines()[-1].split()[-1].split("=")[-1])/1000  # Parse probe output
+            temp = int(round((temp * 9/5) +32))                                  # Convert C-F and round into an integer
+            probe.close()
 
-        probe = open("/opt/devtimer/temp_probe/w1_slave")
-        temp = float(probe.readlines()[-1].split()[-1].split("=")[-1])/1000  # Parse probe output
-        temp = int(round((temp * 9/5) +32))                                  # Convert C-F and round into an integer
-
-
+        except:
+            temp = PROBEERR
 
         # 1-wire interfaces (like the DS18B20 uses) can occasionally
         # return wildly wrong results.  For this reason, we throw away
@@ -156,13 +163,12 @@
         if monitor_temps.CURRENT_TEMP == monitor_temps.SENTINEL:
             monitor_temps.CURRENT_TEMP = temp
 
-        elif abs(temp - monitor_temps.CURRENT_TEMP) <= 20:
+        elif abs(temp - monitor_temps.CURRENT_TEMP) <= 20 or temp == PROBERR:
             monitor_temps.CURRENT_TEMP = temp
 
-        probe.close()
-
         Thread(name="Temp", target=show_temp, args=[show_temp.LED, monitor_temps.CURRENT_TEMP]).start()
-        sleep(1)
+
+        sleep(2)
 
 
 #####
@@ -300,7 +306,7 @@
     sleep(0.3)
 
     # If we're in a compensating profile and out of
-    # temperature range, blink the time display
+    # temperature range, blink the temp display
 
     if show_temp.OUTOFRANGE:
         led.brightness=0
@@ -420,7 +426,7 @@
     # Show the initial temp sentinel
 
     show_temp.OUTOFRANGE = False   # Flag for compensating profiles when temp is out of range
-    monitor_temps.SENTINEL = monitor_temps.CURRENT_TEMP = 999
+    monitor_temps.SENTINEL = monitor_temps.CURRENT_TEMP = SENTINEL
     show_temp(show_temp.LED, monitor_temps.CURRENT_TEMP)
 
     # Start measuring temperature