TPMac

The AC fast cycles (on/off). Pressure check using a 'topping off' kit indicates pressure is good. I can see the switch thru the grill but haven't found any video or instructions on how to access and replace the pressure switch. Given it does blow cold when on and the relay is newly replaced, is my hunch good that the pressure switch is faulty? Is there a builtin valve that allows one to unscrew the switch w/o any loss of refrigerant? Any advice appreciated.
PS
In a search I found the same question 10 years ago but for the most part. it was unanswered.

Ryanthegreat1

Will need to recover the refrigerant before removing that pressure sensor.

A reasonably advanced scan tool will show what that sensor is doing.

TPMac

That helps, thanks. One webpage reported that most cars do have a 'presta valve' feature allowing the pressure switch to be removed w/o losing refrigerant. Seems like a good feature economically, and perhaps environmentally if people are tempted to just replace the switch and then refill.

I do have a "CAN OBDII" scan tool for my 2005 Accord. I haven't tried the scanner b/c I didn't see anything related to pressure switch in the list of codes for a 2005 accord. And a more advanced scanner won't show anything more b/c the data from the 2005 Honda OBD port doesn't include pressure switch info, correct, or?

Ryanthegreat1

It's probably there if you go to an HDS clone scanner. Autel and Foxwell come to mind as inexpensive scan tools that have the factory Honda features.

TPMac

I found the manual for my OBDII scan tool and it does list 10 A/C codes. Crossing my fingers I hooked it up and did the scans. No error codes. There's also the I/M checks which includes an A/C section. But the scanner reported "N/A" which means that my 2005 Honda doesn't support an A/C monitor. Can I assume now that even a more advanced scanner won't find anything more?
The A/C worked fine on a recent 30 minute drive in 85 deg weather but that's consistent with last year when it often worked initially but then would conk out and fast-cycle.

Ryanthegreat1

I don't think your scan tool is capable of reading the pressure switch. It should be a live data stream of the pressure.

If the AC runs for a short period of time and then starts short cycling it could be the pressure is too high because the condenser isn't able to shed enough heat or the expansion valve in the evaporator is failing or icing up.