I may have found the issue...I left the smaller o-ring out of the exhaust solenoid when I put it back together. I’ll test it tomorrow morning.

 

Negative. Still seeing the c1a20-64 and u0421-94 codes. I guess I need a new compressor. sad, because this one doesn't look that old.I ordered an amazon replacement it's the only one I could get here quick enough. Maybe it will give me a good year or so. Anyone know if I'll need any update to the ECU for this one to work?

 

What again did you all do to it? How far did you take it apart? Reed valve in backwards maybe?

There was one ECU update I think for the Hitachi to reduce its operating temperature threshold. But other than that, I think the only "update" is for when switching brands. Hitachi or AMK, one does not necessarily perform better. It was a supply issue. But the very first AMK compressor I came across was sooooo quiet compared to my new Hitachi, even though I have no rubber isolators too.

 

dryer off—new desiccant, filters, o-rings. exhaust solenoid off—new o-rings. cylinder head off—new o-rings and seals. Cylinder off—new piston sleeve and ring. removed overhaul valve bolt and cleaned underneath and replaced o-ring.

I did not take off the cover that gives access to the piston rod bearing as it moved freely in the housing and looked good from above. But for the most part, went thru and changed every o-ring/filter/seal/cleaned wherever I could.

 

The kits usually have a piston sleeve that gets replaced. So it *might* be that the piston sleeve is worn and its not producing enough pressure - basically blow-by. But of course if anything else it off it will not work well. Like I said, the reed valve is critical. Also even the dryer-o-ring can fail if not lubricated when installed.

 

by reed valve you’re talking about the shim between the cylinder and the head with a U-shaped cutout correct? I verified the orientation with the head before I put it on.

 

Yup. Need to be installed the same way it came out, not flipped, etc. Its basically a check valve.

 

Rog. At this point, I’ll double check anything while I wait for the new compressor to come in.

 

I have taken apart a few Hitachi compressors. Feel free to post pics or such, maybe I will see something that you missed?

 

I took a video. thats as much as it runs before It faults out. It seems really loud though.