[s-cars] Coolant temp guage problem

[Dave Ellis]

I'm looking to confirm with those more knowledgable a problem I have 
with my coolant temperature reading.

The coolant temperature guage on the dash has for a while now been 
reading lower and lower, presently about 70-75 celcius.  I initially 
thought it was the thermostat dying, but checked channel 51 via the 
HVAC diagnostic function today and it is claiming a temperature of 
between 86-90 degrees celcius.

So what does the collective wisdom say?  MFTS on the way out, dash guage 
broken, or something else?  It's unlikely the thermostat if the HVAC 
diagnostic is correct.  Is there any possibility the HVAC unit is 
incorrect?

Thanks for your input!
-Dave

'93 S4
'99.5 A4 1.8t