How bad will replacing the heater core on an MK2 with air be

[Vincent Waldon]

So not strictly a diesel question but we're all big fans of DIY here so I thought I'd ask a couple of related questions:

First question: Bentley (and the interweb) have lots of details on a generic heater core replacement (pull the cluster, pull the dash, split the heater box etc etc etc) but all the Bentley says about the job if you have air conditioning is: "don't do it... leave it to the professionals because the A/C system will need to be bled".

The system in question is already "bled" so I'm not worried there... just wondering if anyone else has done it and has any words of wisdom.

Second question:  it was an R-12 system and now that it's bled I have to convert to R-134 or some such... anyone done that and know how expensive it is ?  Looks like new oil, a new dryer/receiver, and some new o-rings on the compressor hoses ??

[jtanguay]

i've switched over to hydrocarbon refrigerant.  works pretty good imo.  its a big process to convert from R12 to R134A, but you can just charge up with r134a... problem being is that the a/c oil will turn to a thick goop and probably either kill your compressor, and or cooling efficiency big time.  not to mention that the smaller particle will just leak right out.

the o-rings that i'd recommend changing are the high pressure ones going from the compressor to the condensor, the receiver drier, and the other end of the condensor.  from there the pressures aren't really above 50-60 psi, although there can be spikes when you shut off the system.

edit: back to changing the heater core  :oops: i'm pretty sure its not that hard with a/c.  the worst part would be sucking the refrigerant out and if the lines are corroded on (which would probably snap off when you try to remove it).   that is only IF you need to remove it...

[commuter boy]

I've done a B3 Passat with air, and it didn't need to be disconnected despite what the Bentley said.  Mind you, I didn't rip the whole dash off either, just
moved it out of the way enough to pop open the heater box and do the replacement.

It was a full afternoon's job, and I had a lovely collection of scratches up and down my forearms by the time it was finished, but I saved hundreds of $$ from what the local shop offered to charge me.

[upchuck]

it's not too bad of a job, the bentley will be a good reference to dash assembly.  keep track of those fasteners and pieces!  simple, but it will take most of an afternoon to pull apart and get back together.  once you start digging in you'll see how everything else fits together.  shouldn't be a problem to pull out or partly disassemble ac if it's discharged.  but rather than recharging it, i just swapped it for a non-ac... way less weight and way more room!