Compressor shuts down at 80 PSI..please help

My on board air compressor shuts down at 80 PSI. I replaced the shut off switch which is supposed to shut off at 150. I thought maybe its getting to hot. It’s not. I checked the air flow. All clear. Please help!

Does it blow a fuse at 80 psi?
Maybe give us a few details about your setup.
Welcome to the forum.

No blown fuse
I run a compressor to a 2.5 gallon tank to blow 3 horn set up
Shut off switch is 150 PSI
it was running just fine until last month
It’s been running blowing fine for 5 years

If you replaced the pressure switch, I’m not sure what could be wrong.
All I can say is check all your connections and clean your grounds.

Ok. Ill check the grounds. It’s odd because when I blow what air I have, the compressor comes on after it drops down to 50 PSI. I do have a gauge connected to one end but isn’t the same as the shut off valve

If you bypass the pressure switch will the compressor come on?

Space for Rent

Ok. Ill try that tonight

Have you double checked the pressure reading is accurate (i.e. by using a new gauge)?

You say it comes on at 50 and turns off at 80…

Before I render an opinion or suggestion, would you be so kind as to tell me what you expected the on and off psi numbers to be? And would you also give me the manufacturer and model number of the replacement pressure switch you installed?

If you have a picture of the pressure switch with these things on it, that’d be even better…

It’s a hornblaster shut off switch. Item#PS-150

And I’m pretty sure the gauge is right. When I would blow my horn at 140PSI It was loud loud. At this pressure it’s very dim like low on air. I used my home compressor and blasts great. Thank you for helping me.

Yes. I expect the on to be starting at 110 and off at 145. That is what is used to do a month ago.

Ok, so it’s this part (HB part #PS-150):

If so, here are some things to consider/check/think about/step through:

How do the terminals of the pressure switch look? Clean, good contacts with solid connections that don’t have much play? If not, clean them and make sure they’re solid not shaky/loose.

What gauge are the wires to the pressure switch and how long are they? If long and very thin, you may need to move up to thicker wire, as undersized wire will heat up when too much current is passed through it … which will then fatigue it. Also consider that voltage drop occurs in 12v systems across long runs of wire – and the way to compensate is to upsize the wire gauge.

Does the ground connection to the body or frame have nice metal-to-metal surface contact with no paint, dirt, or debris around/between it? Is the wire connection to the ground point also clean and solid without much play? If dirty or the connection is loose, clean and/or solidify the connection.

Do you have an inline fuse between your +12v connection and the pressure switch and, if so, has the fuse holder been exposed to water? Look for discolouration of the contact points for the fuse to try to tell. If it has, clean it up … and move it where it’s not exposed to water, because water+current==arc’ing that can actually weaken or melt fuses. Perhaps replace the fuse with a fresh one and try your setup if water exposure may have been an issue.

If dirt, water, or corrosion are a problem anywhere I mentioned … and cleanup resolves the issue … then coat in dielectric grease (aka bulb grease) after clean-up to help prevent this in the future.

And if none of that is an issue or works, then bypassing the pressure switch (as was already suggested) is the only remaining step, really – to see if it’s the pressure switch, itself.

It’s highly unusual that you’ve scored two broken switches in one go. - Anything is possible though. You can easily check whether the switch is at fault with a multimeter or a 12v light bulb and a couple of wires.

Once your compressor shuts off, measure the voltage across the pins of the pressure switch, or if you don’t have a multimeter hook one pin on the switch to your battery and hook the other onto a wire running to a light bulb and then from the light bulb to ground/earth. The switch will basically conduct (i.e. be in the ON position) until it reaches its stated pressure rating and then cut off (i.e. not allow current to flow through the switch pins)

If you have power running through the switch and your compressor has shut off it means your pressure switch is fine and your fault for the early shut-off is some place else.

DBO – I have a question about that. What if the problem is current-related instead of charge-related. I don’t think a voltage test would sufficiently check that to rule out the pressure switch. He’d have to check amperage, too, yes?

The case I’m considering is one where there’s no relay in the mix … meaning power for the compressor is being drawn through the pressure switch, itself, instead of the pressure switch being used to activate a relay that then supplies power to the compressor. As the compressor’s load increases, its amp draw will increase … demanding more current through the circuit … which if the pressure switch is directly in that loop, could be a concern. (As could undersized wiring, poor connections, and the rest of it.)

I don’t know how he’s wired up … nor do I know how HB kits come, so I’m accounting for the worst case scenario, really. It also happens to be a scenario that’d be conducive to burning up pressure switches. (The switch is rated for 30 amps, though. That’s up there. I’ve no idea if electric compressors demand that from their circuits or not … or at what pressures they might begin to come near it. Kinda curious about that, actually.)

The test I mentioned was really a continuity test - and not intended as a check on voltage. The switches internally are really simple and it’s doubtful that it’ll be a cause of high resistance (e.g. burned out internally or fused) since there appears to be some kind of switching going on.
So in that sense, the continuity should be enough to rule out whether the switch is broken or not because you can exclusively reason that if the switch is on - so should the compressor.

The reason for the early shut-down may very well be some place else and could quite possibly be caused by a high resistance somewhere in the circuit (e.g. bad earth). It should still not result in a burned out pressure switch as the circuit itself will not draw more amps than a fully stalled compressor (i.e. it’s max amperage rating).

The smaller Shocker kits (i.e. those using the Viar 275 or 280) had the compress wired directly through the pressure switch, but those were rated at well above the maximum draw of those compressors so they really should never “burn out”.

The OP can perhaps clarify which horn kit and compressor he’s actually got. If it was me, I would work out first if the switch is functioning and then continue on from there. I think all the troubleshooting tips that have been made in this thread are valid though.

Thanks, that was informative. Hopefully it helps the OP, too.

Heck my brown barrel pressure switch has a sticker that says 20amp max.