ACPI thermal _ACx values

Here is the problem.  When I boot up, everything is working fine, and the 
following sysctl is set as follows:

hw.acpi.thermal.tz0._ACx: 3351 -1 -1 -1 -1 -1 -1 -1 -1 -1

Ok, this is fine, except that sometimes the first value isn't 3351.  I have 
seen 3331 and 3341, too.  Is that a big deal?  And, how is this value set?

Now, on to the problem.  When I suspend the machine (S1), and then wake it 
back up again, the first value is changed to -1, just like the other nine 
values, yielding:

hw.acpi.thermal.tz0._ACx: -1 -1 -1 -1 -1 -1 -1 -1 -1 -1

So, if I try to change the value back to 3331, I find out that this is a 
read-only oid.  I found that I can get the value restored by disconnecting 
the AC power (putting the machine in 'economy' mode) and then restoring the 
AC power (putting the maching back into 'performance' mode).

I turned on verbose ACPI logging and here is what I see in the message log:

acpi_tz0: _AC9: temperature 61.9 >= setpoint -273.-2
acpi_tz0: _AC8: temperature 61.9 >= setpoint -273.-2
acpi_tz0: _AC7: temperature 61.9 >= setpoint -273.-2
acpi_tz0: _AC6: temperature 61.9 >= setpoint -273.-2
acpi_tz0: _AC5: temperature 61.9 >= setpoint -273.-2
acpi_tz0: _AC4: temperature 61.9 >= setpoint -273.-2
acpi_tz0: _AC3: temperature 61.9 >= setpoint -273.-2
acpi_tz0: _AC2: temperature 61.9 >= setpoint -273.-2
acpi_tz0: _AC1: temperature 61.9 >= setpoint -273.-2
acpi_tz0: _AC0: temperature 61.9 >= setpoint -273.-2
acpi_tz0: switched from NONE to _AC0: 61.9C
acpi_tz0: WARNING - current temperature (61.9C) exceeds system limits
acpi_tz0: _AC0: temperature 62.9 >= setpoint 61.9
acpi_tz0: switched from NONE to _AC0: 62.9C
acpi_tz0: switched from _AC0 to NONE: 59.9C
acpi_tz0: _AC0: temperature 61.9 >= setpoint 61.9
acpi_tz0: switched from NONE to _AC0: 61.9C
acpi_tz0: switched from _AC0 to NONE: 55.9C

Do I have anything to fear in the -1 value that replaces the 3351 when 
waking up from suspend?

I have searched high and low and found very little information.  Thanks in 
advance for your replies, they are much appreciated.

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