There are a couple of places that you can hear clicking. The blower speed module will click every time it changes speed. The pushbutton module has a couple of relays that are energized by the cold lockout swithc, but only in economy and normal mode, not in total ventalation mode.

The heater blower should not start in heating mode (in-car temp is lower than temp set on dial) below 33 C engine coolant in economy or normal mode. Heater blower motor should start after 33 C coolant temp is attained. If the blower is not starting, pull wire from the coolant lockout switch and ground it. If the heater blower starts after approximately 10 seconds, the themperature switch is faulty.

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Michael LaFleur

'05 E320 CDI - 86,000 miles
'86 300SDL - 360,000 miles
'85 300SD - 150,000 miles (sold)
'89 190D - 120,000 miles (sold)
'85 300SD - 317,000 miles (sold)
'98 ML320 - 270,000 miles (sold)
'75 300D - 170,000 miles (sold)
'83 Harley Davidson FLTC (Broken again) :-(
'61 Plymouth Valiant - 60k mikes
2004 Papillon (Oliver)
2005 Tzitzu (Griffon)
2009 Welsh Corgi (Buba)