Boost pressure switch 25503871

don't see them come up for sale often. Rich Belardi had a couple NOS units for sale in May and June 2023. Sold for $350 each.

suggest you widen your search to include the various f*book groups if you want an OE GM part. and be prepared to pay dearly.

otherwise, model something from the OE part with a readily available hobbs switch from the likes of the link below that give you configuration options. the unit in the link below is $25 and for a few bucks more, change configuration from 1/8 NPT to barb fitting. and it's adjustable.

Or just adapt a generic hobbs switch with some fittings and wiring adapters found via a basic internet search for hobbs switch.


  • GM 25503871 hobbs switch digital dash_FS.jpg
    GM 25503871 hobbs switch digital dash_FS.jpg
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I may sell my backup . It's a used, working OEM switch. They are Extremely rare. PM , if you want ?
......Anthony's suggestion is likely the way to go for you though . I'll work.
Hey Grumpy , How are you
.....Is it new or used ? Just wonder'n ?
If he's not a buyer , I am.
Do we know the pressure settings of the factory switches? Differential press? Cut in -cut out
......2.5 & 10 , on our Hot-airs . I copied this from Vortex awhile Back :

"There are actually two lights that come on under boost.

They work as follows;

light When the boost rises above 2.5 inches of mercury the first setpoint in the round hobbs type switch is reached, it shorts the wht/blk stripe wire to ground to light the first light, when 10 inches is reached the second switch inside shorts the light blue/yellow stripe wire to ground lighting the second."
As far as ' Cut out ', I have'nt a clue ?
Okay, guess the switchs making (shorting) to ground is what I have missed.
I think referencing inches of mercury is confusing for some, should be a PSI figure for boost. Something above zero.
I have a few of these switches, I need to see what these settings are.
Yes it is confusing , but that's what Vortex wrote? Found this also . I trust what John Spina say's :unsure: :

" This design merely indicates low boost (in yellow) and
high boost (in orange). The low boost is preset to illuminate the yellow lamp at 2.5PSI. The
high boost is preset at 10PSI."
Thanks......I do have a used one for backup that I got from Fatnat a couple years ago .so I'm good for now's a good offer for a super rare part.
great info here to confirm how the OE switch is setup for both dash lights and to offer ones from both your parts stashes. a bit easier to use an OE unit than fab a mounting bracket for switches and wiring mods.
I have 2 used way to test them I do not have a digital dash....I will sell them for 50 bucks a piece ....and if they do not work, just send them back to me for refund will just have to chance it ...and eat on shipping back I know you are not a liar