I've been going through a nightmare process of attempting to repair my HCH II AC system. (Symptoms: No cool air, no engine fans at all, AC clutch won't engage)

After locating a used (junkyard) compressor, testing it per service manual guidance (electrical, shimming clutch, testing clutch engagement), installing it, and meticulously reassembling ... the AC clutch still won't engage and now I have a lot of new error codes, among them the dreaded P0A7F.

I'm attempting to work my way through the codes (and the whole compressor nightmare), but I'm wondering how many of these may just be from disconnecting the 12V and IMA battery system and re-connecting? This is the second set of batteries on this car, and there was not a battery error on this (P0A7F) prior ot being unhooked for about 5 days.Is there anything I need to do to reset the battery computer system?

Thanks for anything and everything you guys/gals can offer..

 

Zero.

Disconnecting the 12V clears all codes.

Is the 12V fully charged?

Recommend:

1. disconnect 12V for 5 minutes.
2. reconnect 12V
3. start and idle car until IMA battery stops charging at idle.
4. Do 1-3 a total of 3 times.

06-08 HCH2 notoriously has the 2nd worst hybrid battery ever made second only to the 09-11. Unfortunate, but not surprising a 5 day sit could trigger P0A7F. The above process clears codes and forces the BCM/MCM to force charge the battery 3 times. This + regular driving can restore function to a marginal battery. Your battery would likely benefit from grid charging.

Have you checked the A/C compressor clutch relay?

 

Thanks for the reply and info!

I'll double-check the 12v battery (I think it's fairly new, but I'm unsure of its current charge state)
I've checked the relay when all this started, but it can't hurt to replace/verify again
I'll definitley perform that procedure on the IMA setup.

The current hybrid batteries (I had installed when I purchased the car in April, 2018) were new and from https://www.greentecauto.com/ (that may not matter). Not sure the life expectancy of aftermarket batteries as opposed to new, but I have a feeling they're all horrible ... and of cours my warranty expired last year.

I'll definitely be looking into "grid charging" now, and see if it's something I can handle. TBH, after these month of battling with the AC compressor (special oil, new pump and guages, vacuums, oil volumes, etc. etc.) I'm not sure what I'm up for.

 

Nearly 4.5 years on a replacement is pretty fantastic. If you bought the "upgraded" cells made in China, you're doubly lucky.

 

Your procedure worked flawlessly. Thank you so much!

No IMA light or CEL!

Only code remaining is an AC high pressure code (0533?). I’m REALLY hoping it’s from the jacked up process I experienced (clutch never kicking in, pressure building according to the gauges), and not from me partially crimping the line right by the pressure sensor. NOT a proud moment - when replacing the sensor, I didn’t even think about the structures I was dealing with, and dropped a deep well over the sensor and gave it a crank to loosen it. The whole line pinwheeled and bent. Bent it all mostly back, but a little bit of crimp remains. Guess we’ll see.

Car will be inspected, evac’d, and charged (hopefully) in the morning. I’ll update!

 

UPDATE:
The car is now at a shop and they're working through diagnostics. Thus far they haven't said "you need a new compressor," so that's good. What they have said is ...

"Evacuated system and found 0.36LBS out of 1.00LB, charged system to specifications and found AC clutch engagement was still not present. Checked power and ground and found power not present at compressor, found fuse to have good power, swapped relays and found same issue present. Pulled codes and found multiple codes for thermal protector and P0533 in PCM, following diagnostics tree for P0533 found AC pressure sensor to be above 4.75 volts but when jumping terminals 2&3 that voltage would drop. Next step in diagnostics process is to replace pressure sensor. Possible HVAC control unit problem, need to replace pressure sensor before further diagnostics"

... and charged me $800 for 2 evac/vac/recharges and a new AC pressure sensor. I asked about the AC pressure sensor charge, since it is relatively cheap to purchase and not hard to get to (see attached pic). And he said "it must be a different one, because the book shows 1.4 hours of labor."

I'm not sure what an "HVAC control unit" is or costs, but I'm hoping it doesn't come to that!