Compressor/Pressure switch wiring.

Edited: 10/9/2006 8:40:22 PM by mattsisuzu

Edited: 10/9/2006 8:38:04 PM by mattsisuzu

Edited: 10/9/2006 8:37:28 PM by mattsisuzu

Edited: 10/9/2006 8:37:01 PM by mattsisuzu

hey guys, forgive me if this is an easy one i'm only new to air.
I have an old tired compressor i got from a dude for 50 bucks (Australian) to get me by until i to teh AC pump. I have a 160psi off, 150 on pressure switch.
I have wired it as follows:
battery to relay, relay to compressor, ignition to pressure switch to relay, relay to ground.
The problem i'm having is that teh compressor never turns off. I"ve ran it for a good 30 mins or more and it definately never cuts out (not at all using valves during the fill).

I've put this down to three possible causes.
1 - compressor is too old and can't pump to 160psi
2 - pressure switch is faulty, have tried another 160 switch same results, i am waiting for another 135 off switch in the mail to test.
3-I saw a diagram and it had the Pressure switch wired through the ground line of the relay not the power. In theory the pressure switch should just cut the circut anyway whether its in the power or ground line, but do you think this could be a cause?
Any help would be great, Thanks - from an Aussie who's only new to air!
(mine on the left)

I think your wiring is wrong,your ignition doesnt go to your pressure switch.

He has it wired through his ignition so it doesn't turn on when the truck is off, nothing wrong with that if it was done correctly.

Have you tried a different relay? It may be bad and is stuck closed. Or double check the connections to see that you have everything going to the correct terminals on the relay.

Edited: 10/9/2006 9:18:17 PM by sicpupidaho

the pressure switch has to got to a relay to turn on the compresses.Ingnition can run to relay but the pressure switch needs to go to relay to,not the pressure switch.I can get it out right. ITS A MONDAY!!!

He has it going to the relay. The PS is just getting power from the ignition wire instead of a wire that's hot all the time.

I think you may be on the right track that the pump may not be able to make enough pressure. You didn't say what size tank it is, but running that pump for a half hour is definitely bad news!
Easy way to tell would be to add a gauge to the tank and see what pressure you're getting up to.
As for the relay wiring/ pressure switch issue, does the relay turn the pump off if you unplug the pressure switch? If so, it's most likely not the pressure switch. If you unplug it and the pump keeps going, then something's wired wrong, as you've disconnected the relay's trigger circuit, which should cut the pump's power.
Good luck, and let us know what you find out!

-Phil at FBI

Edited: 10/9/2006 10:53:53 PM by mattsisuzu

Edited: 10/9/2006 10:53:21 PM by mattsisuzu

Thanks guys. Okay so i'll go into a bit more detail. There is a hot constant line from battery to the relay. This then goes through the relay to the compressor. one line then goes to ground. One line comes from the ignition, through the pressure switch to the relay. This is so that the compressor doesn't run when the ignition is off (so my battery doesn't hate me)....

The ignition switch accessory power line also powers teh switchbox. Power is definately there otherwise valves would not work. Also, when you disconnect the switchbox (i have a quick plug connector) it cuts the compressor off fine when disconnected so i'm sure unplugging the PS will do the same (although i haven't fully checked that out).

As i said teh compressor was a temporary until AC is done, i bought it secondhand so it could very well be flogged. Guess i'll know when this smaller pressure switch gets here. Also as said above if the other pressure switch doesn't work i was thinking about using a guage on the compressor.From the air guage in teh cab i have had bout 120psi in the bags and that was after a goot 20-30 mins of filling the tank.

Also it is only a 5gal tank.1/2"up 3/8" down smc valves.

Thanks all for ya help, i'll let you all know how it goes.