aggravation

As long as a TXV meters the same volume, at the same temps, same pressures, across the same operating range required by the different refrigerants then the change would be optional (I don't have the specs for 134a and R-12 in front of me to tell you if they differ enough in this application to matter).
But at that stage of the process why not change out a used part for a new one, it does have moving parts inside of it and it could be close to leaking. The cost of having to do so much of the job again if it fails soon after versus the old 'while your in there' is too much especially if you are paying a shop to do the work.

the flyin' scotsman

Of interest the expansion valve I replaced was date stamped by week and year; 43 87

The new part wasn't date stamped but is marked R134a. Remeber Porsche changed the 928 system from R12 to R134a.............'92 or '93 MY IIRC.

Also, my working R134a system is so cold I've gotta close the centre vent after some running time...........read brain freeze.

ZEUS+

Yes they did change to 134, but there is only one expansion valve part #928.573.123.05 for 86.5 to 95 model years.

Tampa 928s

This was for an 82 is that the same valve?

ZEUS+

Mark the part # for 78-86.5 is 928.573.123.02.

Tampa 928s

For an 82
Paul, will it make a difference if the old one stays in place, if not when and if he changes it the correct one needs to be used I assume. I wonder what the difference is, could it be just the physical size.

the flyin' scotsman

Paul............I replaced the exp. valve as a matter of course not knowing if it leaked or not but wanted to eliminate the part as a potential issue as it was 21 YO. The old part may have been ok but the old black orings were crispy when removed............I guess that many heat cycles will do that.

Appreciate all the advice you gave in helping my car have fully functional a/c.

dprantl

The difference between the old and new expansion valve is that the old one has threads for threaded fittings whereas the newer one has block fittings instead. You cannot use a new expansion valve in an old car unless you also replace the evaporator and the pipes leading from the expansion valve with the newer ones.

Dan
'91 928GT S/C 475hp/460lb.ft

Tampa 928s

Pauls the man!
I am so over helping him on this car when he will not listen to me !
This is my old 82/GTS

ZEUS+

Malcolm you did a thorough conversion and now have great ac. Mark this guy will learn the hard way, hope your car survives him.