I recently had the air filter out of my 245SE and noticed the failed thermostat in the air box had the flap in about the 70%warm/30%cool air position. Since I have never noticed a need for the warm air ( I removed all the exhaust header to air box ducts in my Volvos after learning Volvo had higher than averago AMM failures attributed to the themostats failing and directing hot air to the AMM in the summer).
What I wanted to do was modify the mechanism to keep the flap on outside air always. \
So I removed the mechanism to the worbench, put it in a vise to compress the spring, removed the thermostat, pulled out the actuator rod and substituted a #8 finish nail, cut about a 1/4" shorter. THe thermo fluid leaked out of the thermostat (interesting copper flecked stuff) .
This length of rod (the nail) forced the mechanism to keep the flap closed over the warm air input, so it always ducts in outside air.
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744 & 745 16v 4+OD, 245 SE auto, 242Ti 4+OD, 245DL auto parts car