AC overhaul

[britlude]

Last year I had my AC regassed, but, although it worked, it did struggle when the sun hit the car… if it was overcast, we froze, but as soon as the sun broke thru the clouds, it couldn’t keep up…. When I got the car, nearly 20 years ago, we froze all the time, so it was time to refresh the AC system….


I have been running grills in the front vents for years, but, of course, they weren’t there when previous owners drove the car, so I knew there was some battering to the condenser radiators, so a pair were ordered from amayama, along with the flexible hoses to the AC compressor…


Grotty AC pump
IMG_20180713_112017 by NSX Jon, on Flickr

The new pump from RockAuto
IMG_20180713_105605 by NSX Jon, on Flickr


The pulley to body measurement of the original pump….
IMG_20180713_111919 by NSX Jon, on Flickr


The pulley to body measurement of the new pump
IMG_20180713_111846 by NSX Jon, on Flickr




To use the new pump (later spec to move it further from the exhaust pipes on later cars) I needed a new spec bracket, that came from Christian at ATR in Austria…
37629818_1172630259543344_9145779608656805888_n by JON SUTH, on Flickr


Eagle eyed amongst you will notice that the AC pump pix are from 2018…. Yup, that’s how long it’s been since I wanted to do the swap, the AC pump has been noisy in operation, and a little annoying… it’s not got any better in the last 6 years!

[britlude]

Step 1… degas!!!

Now some would just vent the R134 to air, but I’m not some, so it was degassed properly

IMG_20250307_143911 by JON SUTH, on Flickr

840ml of refrigerant removed, so the system was full, not leaking, just inefficient!

Step 2… the front end

As it was unseasonally warm on the 8^th and 9^th of march, the planets aligned with it being a weekend, and I could get on with it without freezing my bits off….

Car front jacked up…
IMG_20250308_091841 by JON SUTH, on Flickr

Sidelight/indicators removed (little more awkward as I have extra wiring going to them for the DRL system, but they were on connectors already!)
IMG_20250308_092916 by JON SUTH, on Flickr

I wasn’t sure about taking the bumper off…. But it was surprisingly easy to take it off with the bumper support beam and washer bottle…
IMG_20250308_101202 by JON SUTH, on Flickr

And quickly the passenger condenser was off…
IMG_20250308_101202 by JON SUTH, on Flickr

[britlude]

the unit on the little bench…
IMG_20250308_104718 by JON SUTH, on Flickr

A couple of reference pix, so I knew what went where
IMG_20250308_104637 by JON SUTH, on Flickr

IMG_20250308_104642 by JON SUTH, on Flickr

And it was quickly back together
IMG_20250308_113012 by JON SUTH, on Flickr

Forgot to take a pic of the separate bits, but remembered for the drivers side
IMG_20250308_121118 by JON SUTH, on Flickr

Note the battered matrix, and the missing pipe end…. One didn’t want to come apart as it should, and it was easier to separate it and work on unscrewing it with the unit out of the way… I put some thread lube on when I reassembled it, to avoid such things in the future! (hopefully never in the future!)

[britlude]

Then it was just a case of refit
IMG_20250308_142407 by JON SUTH, on Flickr

And put the bumper back on…
IMG_20250308_150007 by JON SUTH, on Flickr

With added lense flare!!!!

[britlude]

Step 3… the rear end!

Car up on ramps, front end jacked up on axle stands, and the removal process begins, cross braces, tie strap bits and eventually the front cross bar of the subframe, that has the engine mount on it, all have to come off to gain access…. The engine mount bolt is pretty inaccessible especially with tubular headers, so I unbolt the engine mount from the engine… soon it’s on the vice…
IMG_20250309_105401 by JON SUTH, on Flickr

Original R12 unit!
IMG_20250309_105410 by JON SUTH, on Flickr

Hmmm grotty…. And I need the top bit….. sooo….
IMG_20250309_105931 by JON SUTH, on Flickr

[britlude]

The new and the old, both brackets in the same place, the compressor moved up, and the difference taken up in the offset of the pully, so that ends up in line with the crank…
IMG_20250309_110538 by JON SUTH, on Flickr

The instructions are to drain the new compressor…. 140ml
IMG_20250309_112343 by JON SUTH, on FlickrIMG_20250309_110538 by JON SUTH, on Flickr

The drain the old compressor and take that from 140 and add it back into the new pump…. This came out of the old compressor…
IMG_20250309_115343 by JON SUTH, on Flickr

Hmmm….. apparently this is common according to the AC man!!! The NSX needs 160min, 180 max, so I put 100 back in, and then after discussions with the AC man, we added the other 40, allowing for some in the evaporator and long plumbing lines….

As I was changing the hoses too, it was easier to remove them with the compressor, than try to unbolt them from it with it swinging under the car…. And I spotted a polished bit on the chassis…
IMG_20250309_115204 by JON SUTH, on Flickr

Hmmm… so the foam had gone…. And it was working its way thru the rubber!!!
IMG_20250309_115236 by JON SUTH, on Flickr

[britlude]

So glad I got new hoses….. however, some time they had tweaked bolt lengths (probably as R134 runs at a lower pressure than R12) so the clamp heights are 8mm shorter….. ok, make up 4x8mm spacers
IMG_20250309_115005 by JON SUTH, on Flickr

Compressor hole!
IMG_20250309_115709 by JON SUTH, on Flickr

All back together….
IMG_20250309_133701 by JON SUTH, on Flickr

Hoses connected up….
IMG_20250309_133707 by JON SUTH, on Flickr

[britlude]

And back to aircon direct for the regas….
IMG_20250314_091750 by JON SUTH, on Flickr

Vacuum the system and do the leak test…. (cross fingers I did all the connections properly)
IMG_20250314_092943 by JON SUTH, on Flickr

All good, phew, and recharge the system!
IMG_20250314_095328 by JON SUTH, on Flickr


So now I have a freezing car (and it’s not as warm as last weekend!) and it doesn’t sound like a bag of spanners everytime the AC compressor kicks in, in fact, I can only tell seeing a slight drop in the engine rpm! So all good, and only 6 years in the making!!!

[Heineken]

Thanks for the write-up - gotta use the time when the server is up

[PeterW]

Great thread. Thanks Jonathan for sharing your knowledge!