How do I remove the cover on my Hitachi air compressor

if you replaced capacitor exactly like it was remove and no wires switched you have a bad motor.

If u are talking about the bleed off that blows when the compressor shuts off. It should blow down for a short period then stop. If it dont stop your tank check valve is bad.

There is no battery on that air compressor.

The pressure regulator can easily be replaced by removing the large plastic decorative cover. The manifold behind the cover is the part where the regulator , gauges, and quick connects are attached. The manifold is fed air from the pump via a plastic hose connected to the pressure switch. The regulator sells for about fifty dollars. This part usually fails in two ways. It leaks air from the knob or no air pressure will reach the quick connects. If your problem is no air at the quick connect, you can do a temp repair by removing the safety valve and installing a tee fitting at the port. On the tee fitting reinstall the safety valve and a quick connect on the other fitting. This will give you tank pressure . Good luck.

Find the pressure switch. Remove the cover and loosen the spring loaded nuts on-till the switch opens. Readjust for the pressure you need. Keep it below the amp rating on the motor to keep the breaker from tripping. (RLA or FLA).

I just looked a the owners manual, did not see a reset, try taking the plastic cover off and see it the motor has a button on it to reset the motor, the motor may be damaged also, always try to use a direct connection to the wall outlet for power, Hitachi air compressors dont like extension cords.

The early Hitachi EC89's came with a 40 microfarad capacitor to start the motor. This is insufficient when its cold, or the compressor hasn't been used in a while, or the compressor is still in its break-in period. Hitachi later changed it to a 60 microfarad capacitor, as it now is with the currently offered EC89's, which provides reliable and consistent starts of the electric motor. FYI: the capacitor is the white tube looking thing just under the black cover on the top side of the compressor. You can just see it without disassembling anything if you peek under the black cover to the best of your ability. To get at it you need to remove the black plastic cover. To do that, it takes about 20 minutes of disassembly time and a few tools: unplug the compressor, disconnect at least one end of the copper pressure tube (the tube that runs from the pump to the tank), remove the four main bolts that hold the black steel compressor base to the main frame, now you can get at the four phillips head screws that hold the plastic cover on, loosen (but don't remove) these four phillips head screws, then pop off the plastic cover (there are anti-vibration side locks that need to be disengaged- by using a long flat head screwdriver from the inside- to pry them and pop them off from the inside). Once the black cover is loose, you will either have to reach in and disconnect the two wires to the breaker, or unthread the breaker's little hex nut and separate it from the black cover. Replacing the 40 microfarad capacitor with a 60 microfarad capacitor (available at your local electric motor rebuilder- yellow pages) will resolve the problem of the weak starting motor that pops the breaker before the motor gets a chance to start rotating. Shame on Hitachi for not publishing this fix themselves.

Try at eReplacementParts.com : Power Tool Parts and Tool Repair Diagrams.

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what type of air compressor you have,since when you maintained it

There should be a pressure switch adjustment under the cover of the switch remove the cover and reset.