refer first to fig1 . illustrated there is a control module 10 for a power seat system of a motor vehicle . such a module takes inputs from various control switches and seat position sensors and drives the motors which position the power seats . frequently , it is desirable to package control module 10 under a seat in the motor vehicle , for maximum packaging efficiency . control module 10 preferably has a molded plastic housing within which is housed a circuit board containing the control circuitry which controls the power seat motors . several holes 20 , 22 , 24 and 26 are provided in the bottom of the housing of control module 10 ( see fig2 and 2 a ). holes 20 , 22 , 24 and 26 are located directly opposite capacitors 30 , 32 , 34 and 36 , which are located on the circuit board within control module 10 . refer now additionally to fig3 for a description of the circuitry within control module 10 . the circuitry includes control circuitry 40 which performs control of the power seat motors . control circuitry 40 preferably includes a microprocessor . control circuitry 40 controls one or more relays 44 via control of relay coils 46 and 48 . relay contacts 50 and 52 are coupled to a power seat motor 54 to effect bi - directional control of power seat motor 54 . additional relays and power seat motors are also controlled by control circuitry 40 as appropriate . power for relay coils 46 and 48 is designated v cp in fig3 . v cp is provided via a fuse f 1 from v bat , the battery voltage in the vehicle . fuse f 1 is included in a fuse holder having terminals 56 and 57 . control module 10 also includes moisture protection circuitry 58 . moisture protection circuitry 58 includes a plurality of moisture sensing locations 60 , 62 , 64 and 66 , which are located on the circuit board within control module 10 . ( preferably , the circuitry of fig3 is of “ surface mount ” technology .) each moisture sensing location includes two solder pads ( for example , solder pads 60 a and 60 b of moisture sensing location 60 ). also , for noise immunity , each moisture sensing location includes a capacitor coupled across its solder pads ( for example , capacitor 30 coupled across solder pads 60 a and 60 b ). it is noted that any insulating coating which may be applied to the circuit board is not applied to solder pads 60 a , 60 b , 62 a , 62 b , 64 a , 64 b , 66 a and 66 b ; it is through these that moisture intrusion into control module 10 is sensed . moisture sensing locations 60 , 62 , 64 , 66 are coupled to a pull - down resistor r 4 and an r - c low - pass filter comprising resistor r 3 and capacitor c 5 . the output of this filter is coupled to gate 70 of field - effect transistor ( fet ) q 1 . drain 72 of q 1 is coupled via a resistor r 1 to fuse f 1 . fet q 1 and resistor r 1 are selected such that when fet q 1 is fully “ on ” ( that is , fully “ enhanced ”), the current drawn through resistor r 1 and fet q 1 is sufficient to “ blow ” fuse f 1 . drain 72 of fet q 1 is also coupled , via resistor r 2 , to the base 80 of p - n - p bipolar transistor q 2 . emitter 82 of transistor q 2 is coupled to v cp , and collector 84 of transistor q 2 is coupled to the outputs of moisture sensing locations 60 , 62 , 64 and 66 . capacitor c 6 , along with resistor r 2 , form a low - pass filter which improves the noise immunity of the response of transistor q 2 to actuation of fet q 1 . zener diode z 1 is provided to protect gate 70 of fet q 1 from voltage transients which may exist , for example , in an automotive environment . the moisture protection circuitry 58 of fig3 operates as follows . if sensing locations 60 , 62 , 64 and 66 become sufficiently dampened by moisture , the conductivity between their respective solder pads ( e . g ., solder pads 60 a and 60 b of moisture sensing location 60 ) increases . the voltage across pull - down resistor r 4 thus increases as well , increasing the voltage at gate 70 of fet q 1 . with a sufficient voltage rise at gate 70 , the resistance between drain 72 and source 90 of fet q 1 will decrease , causing significant current to flow through resistor r 1 . if the voltage at gate 70 of fet q 1 is large enough , the current flowing through r 1 will be large enough to cause fuse f 1 to “ blow ”. power for coils 46 and 48 of relay 44 ( and coils of other relays also controlled by control module 10 ) will thus be removed . inadvertent operation of power seat motor 54 due to moisture infiltration into control circuitry 40 of control module 10 will thus be prevented . transistor q 2 has two major purposes . first , if the voltage at gate 70 of fet q 1 has risen only to the point that fet q 1 is only marginally conductive enough to blow fuse f 1 , transistor q 2 will ensure that the gate voltage of fet q 1 rises enough to blow fuse f 1 . this is accomplished because , with a modest current flowing through resistor r 1 , the emitter - base junction of transistor q 2 will become forward biased . this will cause current to flow from emitter to collector of transistor q 2 , increasing the gate voltage of fet q 1 . this positive feedback , wherein fet q 1 beginning to turn “ on ” turns “ on ” transistor q 2 , which in turn more fully turns fet q 1 “ on ”, ensures that fuse f 1 will blow when moisture is sensed by moisture - sensing locations 60 , 62 , 64 and 66 . the second function of transistor q 2 is to ensure that the voltage v cp is held low even if conductivity between terminals 56 and 57 exists after fuse f 1 is “ blown ”. it has been observed that in the presence of fluids with relatively substantial conductivity , such as salt water , significant current can flow between terminals 56 and 57 even after f 1 has blown . such current may even be sufficient enough to power coils 46 and 48 of relay 44 . however , if v cp remains at a significant voltage even after fuse f 1 has blown , the emitter - base junction of transistor q 2 will remain forward biased . transistor q 2 will thus continue to conduct , ensuring that fet q 1 has sufficient gate voltage to heavily load v cp , which would have a very high source impedance . under these circumstances , v cp would not be sufficient to power coils 46 and 48 of relay 44 . two other design considerations should be noted . first , several components ( most notably resistors r 4 and r 1 and fet q 1 ) can be selected to adjust the sensitivity of moisture protection circuitry 58 as appropriate . second , q 1 &# 39 ; s selection as an fet , as opposed to a different type of semiconductor device , is advantageous because the typical failure mode of fets due to thermal failure is to fail conductive . that is , if fet q 1 fails due to thermal “ overload ”, it will tend to continue drawing current through resistor r 1 . this will provide continue to load down v cp , providing a “ fail safe ” situation . various other modifications and variations will no doubt occur to those skilled in the arts to which this invention pertains . such variations which generally rely on the teachings through which this disclosure has advanced the art are properly considered within the scope of this invention . this disclosure should thus be considered illustrative , not limiting ; the scope of the invention is instead defined by the following claims .