cooling

[Alan Dowless/SYBASE <Alan.Dowless@sybase.com>]

Quattro List,
 I have an '87 5000QT.  I have replaced the radiator (the plastic hose knobs 
broke off) and replaced the thermostat with an 87C unit.
 When I drive in 85-90F weather with the A/C on and in traffic, the third stage 
radiator fan comes on frequently.  When this stage comes on the whole car 
vibrates and is very annoying.  I am worried that the fan will burn up along 
with the wiring if this 3rd stage runs too long or too frequently.  BTW, the 
3rd stage generally comes on just after the gauge needle passes the straight up 
center marking on the face of the gauge.
 Has anyone experienced this situation?  Is the 3rd stage fan meant to come on 
in normal driving?  I thought it was there as a last resort because it has it's 
own relay.
 Your comments will be appreciated.

Thanks,
"Autlaw"