typ44 TQ question

[JordanVw@aol.com]

hi..i've just replaced the coolant expansion tank on my '86 5kTQ with a (what 
was thought to be) good used one for the second time...  i drove the car 
around for awhile, and then the coolant warning light came on in the 
autocheck display again!!  I find it alittle strange that both coolant level 
switches at the bottom of both used tanks were bad..but you never know, with 
used parts.
the car is Not running hot. the coolant level is fine.  why else would the 
coolant light come on? I will order a new expansion tank, if the problem is 
indeed the switch, but i just wanted to check with the conventional wisdom of 
the list, first. 

also, on another note, i usually have the dash computer set to show the turbo 
boost pressure, on the dash.  but today, everytime i start the car, it resets 
it to the mileage display, and it blinks.   i can reset it to the boost gauge 
by hand but it keeps going back to "mileage" everytime i start the car.    
any ideas?

chris
'86 5kT, TQ