I was told the governor on my Volvo is fixed, welded and cannot be adjusted. Can I just put another brand in there? Apparently it has an "inversion valve" what does that sucker do? I saw it hanging below the governor.

Maybe I should just bypass the damn thing.

What I want to do is fill my trailer tires to 120 psi. Currently the governor kicks on at 100 psi and off at 120 psi. I get maybe 116 psi at the air chuck.

If I were to put a valve in the system to bypass or shut off the governor, where would I put it? I guess this is a no no though.

Without seeing what you have I am not sure.

A conventional governor has a plastic cap, under the cap is a set screw and a lock nut, loosen the lock nut and turn the set screw in, this will increase the pressure that the governor kicks out at.

My air gauge will go to 130 lbs when mine kicks off

I know the ones you're talkiing about allan. They look like a normal one but have the set screw bolt cut off flush with the jam nut so you can't adj it. All the ones I've seen bolt right to the drier and they do have an extra valve behind them.
Not sure exactly which line it would be on your Volvo if you have more than one. Also not sure if your governor is mounted to the compressor or external. Basically you would be looking for an unloader line/port.

Mr. Patterson could you turn a little to your left. Now take one step back. There, The governor is adjusted. Carry on.

We also adjusted your air gauge. It was 4 lbs off.

If you get a Bendix exchange governor it should be adjustable, look under the plastic/rubber boot at the adjusting scew, if it looks like it was cut off with bolt cutters it won't be adjustable.

There would be another way around this but not recommended.

Is this a holset compressor? I would avoid bypassing, it often creates new, more complex problems.

When the compressor reaches cutout pressure, an air signal from the governor's UNL port unloads the compressor... stopping air production.

Why in the world do you want to put 120 psi in your trailer tires? Is it just to seat the bead or do you plan on running at that pressure? I'd hate to be in front of you when your deadheading in the rain!

You could drive to Manitoba, put in 116 psi then drive to Brownsville, TX and your tires would probably have at least 130 psi in them! Or use your shop air compressor.

Seriously you need to consult your tire mfr.'s load inflation tables.