diff --git a/afsk/main.c b/afsk/main.c
index 0d8357fc..8c00fbe4 100644
--- a/afsk/main.c
+++ b/afsk/main.c
@@ -1394,7 +1394,8 @@ if (sim_mode)
 	    	voltage[count1] = voltage_min[count1];
 	    	current[count1] = current_min[count1];
 	    }
-	    sensor[count1] = sensor_min[count1];
+	    if (sensor_min[count1] != 1000.0;	 // make sure values are valid
+	    	sensor[count1] = sensor_min[count1];
 	}	
     }
     if ((loop + 4) % 8 == 0)
@@ -1410,7 +1411,8 @@ if (sim_mode)
 	    	voltage[count1] = voltage_max[count1];
 	    	current[count1] = current_max[count1];
 	    }
-	    sensor[count1] = sensor_max[count1];
+	    if (sensor_max[count1] != -1000.0;	// make sure values are valid
+		sensor[count1] = sensor_max[count1];
 	}	
     }