Tecmark Pressure Switches 3900 Series 3902 3903

Tecmark 3900 Pressure Switch

Tecmark 3900 Series pressure switches are found in numerous pool & spa heaters, variants such as the 3902, 3903, 3903-BP & 3903-DF are common and will be located on or around the heater assembly. A pressure switch is a simple on/off device which controls the heater operation. 
These pressure switches use an internal diaphragm to convert a water flow pressure signal to an electrical signal. This electrical signal will open or close (based on manufactures design) the heating circuit when the pressure set point is reached. 

Tecmark pressure switches are made in the USA & are UL Recognized & CSA Certified as an operating, limit or safety control with SPST switching logic.

Variants:
3902 - 1Amp, 1-5psi Adjustable, 1/8" NPT (Universal) [Click to View]

3903 - 1Amp, 1-5psi Adjustable, 1/8" NPT (Univ. w/o screws) [Click to View]
 
3903-BP - 3Amp, PSI Factory Set Non-Adjustable, 1/8" NPT [Click to View]

3903-DF - 1Amp, 1.5psi fixed, 1/8" NPT w/o terminal screws [Click to View]

3902 Pool heater kit - 1Amp, 1-5psi Adjustable, 1/8" NPT (Universal) w/ brass adapter fittings. This kit is used to replace the following pool heater pressure switches, 3900, 3901, 3903, 3904, 3906, 3909, PRS-1100, PRS-1101, M3218, 71076, 26775, 26776, 26778, R-113, R-130, R-132B, S-1921173328, B600025, 600025, Comfortzone, Hobbs, Laars, Purex & Raypak [Click to View]

Tip# If you find your pool or spa heater is not working check both the pressure switch and the relay to which it connects. Usually it will be one of these two parts that has failed (if not the heater element) if you're getting the 'heater on' indicator light its the element. No 'heater indicator' means that heat is called for but the heater is not responding. 
The pressure switch sends an electrical signal to the heater relay which allows the heater to turn on/off.