Friday, March 8, 2013

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.

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.


  1. This comment has been removed by a blog administrator.

  2. question: I just took out of my SPA a 3903-BP, however on the label it says 1 Amp (120v) and not 3 Amps. I also have a hard time finding the BP version. if I were to use a universal (such as the 3903 or 3902) where should I set the PSI? I mean what is the factory setting for 3903? is it application dependent?


    1. The 3903-BP can be found on our site here :
      The -BP has a 3 Amp rating vs. the standard 3902/3 switches that are 1Amp. As 1Amp is shown on your switch you could use either as a replacement.

    2. Hi Terence, thanks a lot for your help. I was just wondering, since the one I have says "BP" but also "1Amp", if by buying the BP on your website I might be getting something wrong, while if I by the universal one I have no idea what pressure to set it on (it's for a hot tub), would it be around 2/3 PSI? would the BP one be set on the pressure I need by default?
      thanks again for your time, you're super helpful.

  3. This comment has been removed by the author.

  4. 99% of the time the 3903/3092 will work with out any adjustments.
    Should you need to adjust it the process is simple - turning the screw on top of the switch left or right until the heater turns on.

  5. guess I'll do that then, although I have no way of knowing if the heater is on other than filling up the hot tub and making it go for a bit. Plus I'm not even sure the pressure switch's the issue, I'm just trying out stuff...

    I'd take the BP, but not being very strong on electrical stuff I'm not sure what the "3Amp" labeling entails, and since mine clearly says "1Amp @ 128 VAC" I'm worried that the BP I see there won't be right.
    thanks again


  6. Tightening the screw makes it more or less sesitive?