I'm just looking for two quick answers. Thanks.

How does the Hobb adjustment work (i.e. screw in the adjuster means it activates at a lower or higher pressure)?

Can you wire a switch to a Hobb switch to turn things on manually (it's not for nitrous, don't worry)? I've read the switch was normally "opened" (allowing current flow) so how do you "close" it? Thanks and take care.

Eric

 

Anyone???

 

Well you could wire one to control whatever you want it to..
Preferably using it to trigger a relay..
Also:
NO[normally open] means OFF[ no current flow]
NC[normally closed ] means ON [current flow]
You 'close' a NO Hobbs switch by applying the appropriate pressure..[fuel,oil,air, etc] which 'closes' it from 'normally open'..
Relays work on the same principle.. NO or NC, and you can wire it either way you want it to work, using different terminals..
So you can use a normally open Hobbs to trigger a relay, and then wire the relay circuit normally open or closed, whichever you need..

I believe screwing IN increases the point that the switch opens.. [99% sure]
Confused yet?

 

Sorry, I think I may have worded the question wrong. Or I'm confused (which happens frequently!!!)

Can I manually turn on/off the hobb switch using a switch inside the car (like purge but actually activating the hobb switch)?

And from what your saying, if I have a range of 3psi (min) to 28psi (max), I'd unscrew the adjuster (little set screw in the middle) to move towards the 3psi range and screw in to move towards the 28spi range? Sorry I'm asking it all over again, I'm just a dolt with electronics and my buddy lost his directions. Thanks and I appreciate the advice/info.

 

You know what one does right?
It's usually used as a 'safety precaution' in the event that if you lose fuel pressure the nitrous won't 'activate'.. ]
Bypassing it would be to wire a switch in parallel [effectively bypassing the switch]
Yes out is less, in more..
What are you trying to do with it exactly?

 

I'm trying to troubleshoot the switch for one. I've applied pressure using my compressor and can't seem to activate the damn thing. It's for his water injection. It's supposed to sense boost (we want it set low) and start spraying the mist. So I found a bad wire, fixed it, attached an LED inside the car to show it was "on" and it didn't work. So I figured I'd wired it wrong (checked the LED, it was fine, checked the schematic, it was fine so I thought I'd try to force the thing to work via pressure/boost from the compressor and never got the pump to turn on. So I though bad pump or bad hobb switch. Tried another power source (directly to the battery) and the pump misted like it should. So I thought bad switch and thought I'd see if I could rig a switch to turn it on manually or maybe thought I had the pressure jacked way to high and came looking here for help. Tada!!! So any pictures (I'm a dummy so they help)? If I hooked it to the pink wire on the gray coil plug it'd mist as soon as I turned the key on. With it hooked to the pink wire on the black plug I can't get it to come on at all. So I'm kinda baffled. Maybe the gray plug is right but the switch needed to be adjusted lower. *scratches head* Sorry for the babbling.

Eric

 

Well testing with a air compressor should activate it!..
Is it a known good switch?
One I have here says NO and has 2 screw terminals on it..
THey Do make NC ones also tho .. look on yours to be sure which you have..
All it does is close the switch when the pressure is sensed..
Maybe the switch is bad?
If you put it in an air compressor, and ran the pressure up, and it didnt close, then I'd say it's bad..
Where do you have this thing screwed into to 'sense boost'?
Not familiar with 'water injection' [or overly with boost] but I suspect boost is really rather low PSI[may not be enough to activate the switch?]but the air compressor should have activated it..
Look here for a bit of info on the switches, and pix:
http://content.honeywell.com/sensing.../catswitch.asp

This pdf lists all the switches and specs:
http://content.honeywell.com/sensing...scorp/P3_6.pdf

 

Thanks for the link. I found a shot that really helped my minds eye. The thing that messed with me was when I was able to get the pump to run hooking either to the grey coil plug (pink wire) or directly to the battery. I'll troubleshoot a little more.

 

An added thought here...
Check carefully which switch that you have[from here]
http://content.honeywell.com/sensing...scorp/P3_6.pdf
For instance, I have a 76053 which is a '2 screw terminal, NO [normally open] 25-50 lb range, + - 5 PSI error margin'..
I thought of this due to if you used MY switch it'd never activate with 'boost'...
It's for fuel pressure detection to shut down nitrous should fuel pressure drop off...
Just a guess but you would need a NO[you want the switch to 'sense boost and turn ON'] 78144 '2 screw 8-13 psi + - 2psi error margin'
In all likelyhood your switch is 'too stiff' [will never activate..]
Post up what switch # you have.. and exactly what the PSI is when you're 'on boost'... then the above chart will tell which you need..

 

Here's the info on the switch. It's designed and packed as part of his kit (not something we're fabbing ourselves).

Normally closed pressure switch
P/N 806157
Factory set @ 10psi (adjustable from 3psi) .25A
V01246
V48/.5A
18 BSP NK PMN 2CV Made in Italy

Any of that help?

 

Well it isn't a Hobbs[so the link I gave isn't gonna help a lot]
The PSI seems within OK range there..[3-10 or so.. again I am not that versed in boost..]
What sort of jumps out at me here is that it's NC or Normally Closed [ON, or closed].. [you say 'normally closed pressure switch' ]
That means that applying pressure OPENS it..[turns it off, opens the circuit]
Not sure how it works with what you are doing, but that seems a little odd...
Is there a relay this thing works with?
If so, it could be that it being 'closed' holds the relay contacts 'open', and when it 'opens' the relay 'closes' to activate the mist?[it could be wired that way..]
Seems odd to me tho?..
Do you have a multimeter or test light?
See if the switch at rest is making[closed].. then try to open it with air pressure etc see if it opens[turns off ]

 

Yep, it's relay equipped, has a nice harness and everything is bundled together as a kit. It's designed to work as shipped but I see what you're saying about it being a little odd that the thing is "normally closed". I am thinking, like you said that the relay makes it all work. I do have a multimeter and test light. I get more confused though, the more I think about it. LOL I would just think that using a compressor that I'd be able to force the switch to activate using 20-50psi!!! When I really want it to turn on around 3-5 psi (his kit is only making 6). Baffled but working on it. Your ideas, links and questioning though has really helped. Thanks and feel free to keep it coming.

 

That switch info you posted says it's factory set at 10psi, and adjustable from 3 psi.. turn the adjuster out [CCW] to lessen it from 10 psi..
If set at 10 and you want it on at 3-5 and the kit is making 6PSI boost it'll never come on unless you lower the setting..
An air compressor should surely activate it[remember it's always on and activating it turns it off]
Are you screwing it into the air compressor?[ I would think standard pipe thread fitting]if that doesn't turn it OFF then it's faulty..
Is it ON when at rest?[should be]