90 minutes is, in a word, amazing. But I guess it is entirely possible if you've done it a few times. Was it on multiple cars, or were you having persistent problems behind the dash?
It took me 30 minutes just to get the right side connector on the back of the gauge cluster to release...
This spring, I noticed that my heater would only blow warm to hot air in the "HI" temp setting on the HVAC panel. Is there anything you can think of that I should look for as long as I'm in there? Many thanks...

 

Always the same car... unfortunately....
Not knowing what else might be wrong, I'm thinking it is most likely a defective HVAC controlling unit in the ski slope - very cheap on e-Bay. While you have them exposed, you also might want to check the blowers, to make sure the fans and vents are working properly.

 

So, did you have a problem with the AC blowing warm or what led you to the valve? The reason I ask is I have had everything from the firewall forward redone and the A/C works well below about 78 F. above that it has problem. So, I'm not sure if that flaps are malfunctioning or something else

 

I had a blown filter that contaminated the whole system, including the compressor. Little desiccant beads all over, clogging the valve, lines and condenser. A real nightmare.
Did you check that you haven't lost any freon? If freon is good, then it sounds like you might be blowing hot air at the same time as cooling. Definitely check the flaps first, but also the control panel.

 

Unfortunately I've discovered the same issue with my system today. But thanks to your posts and photos I had the confidence to tackle this diabolical job. Greatly appreciated Guillaume!

I undid a handful more electrical connectors so I could remove the dash completely. Already disconnected about a million, so a few more wasn't a big deal!


Found I could get all the parts off Ebay easily - evaporator, TX valve, condenser, compressor seals kit and receiver/dryer - and at good prices.

 

You are most welcome. I was happy to see this worked for a RHD as well. Out of curiosity, how much did you end up paying for all the parts you just purchased?

 

Guillaume,
The prices I paid, excluding shipping costs as that is so dependent on where you live, was:
Evaporator & TX valve $108 USD
Condenser £87 GBP
Compressor Seals Kit $23 USD
Receiver/dryer £20 GBP

So not to bad I thought even with the shipping costs. I've had more expensive hobbies!

 

Electrical connections on one side of the transmission tunnel.



Sockets on the other side of the tunnel



The yellow leads near the A pillar need to be unplugged and the earth leads from the earthing piont of the top of transmission tunnel.



These leads have to be unplugged from the other A pillar. I had to unbolt the engine ECM to access one of the plugs




Just thought these photos, in addition to Guillaume great description would help anyone wishing to remove the dashboard completely

 

Hi,
Just a couple of other things I learnt that may make it easier for someone recommissioning their X300 A/C:

Putting a new seals kit through the compressor is easy and reasonably cheap. I found Century Air in Arizona great to deal with and cheap for parts. Their Youtube "DIY" videos are good too. I expected to find my compressor full of beads like the high pressure hose to the TX valve but only found one bead inside! Just remember to install the front seal with the "lips" pointing into the compressor body. Don't ask how I know.....

The service ports are a ball type that was commonly used on 90's Fords and GM cars. Once you know that you can find replacements on eBay or from Century Air.

The system needs 180ml Denso ND8 oil, which is a PAG46 type oil. Again I could buy a small can off eBay that also gave me enough to replenish the system and lubricate all the o-ring seals.

I was able to clear all the lines with compressed air and acetone except the high pressure one between the receiver/dryer and the TX valve. It was just far to clogged to clear. However I was able to buy an aftermarket URO brand one off eBay at a reasonable cost.

Also recommend you take some photos of the nut and bolt combination at the dash end of the struts that brace down to the transmission tunnel. I didn't have any trouble with reassembly but that was purely good luck I could remember as it's not obvious the order and orientation. Similarly, recommend taking photos of the outside of the evaporator case just incase you forget where something goes on reassembly.

How's it perform?

Fantastic! Very happy with the results.

 

Is the heater core inside that box with the evaporator assembly?