AC Service Port Question
07-17-2017, 01:26 PM
#16
Rennlist Member
The high and low R12 ports are the same size (at least on my 85 928 and also my 84 911), so the adaptors could easily be installed on the wrong ports. The large diameter high side R134a adaptor typically utilizes the original Schrader valve in the R12 port so can be removed without effecting the vacuum or charge in the system. The small diameter low side adaptor may or may not be installed over the original Schrader. Some people remove the original Schrader and install the adapter with the Schrader in it. The other option is to install the adaptor over the Schrader and either have a floating pin or second Schrader in the adaptor that presses down the originsl Schrader when the manifold fitting is turned to open the port. If the original Schrader was left in place this adaptor can also be removed without effecting the charge.
07-17-2017, 02:42 PM
#18
Rennlist Member
If they are "push on" type, then R134 was used, and you should be able to just switch them as they are most likely hollow adapters w/o valve inside and still use the original R12 valve.
Ive seen some where only one "push on" was left in-place and the other was still a screw on, all depends on the quality of work of the last person in there
Ive seen some where only one "push on" was left in-place and the other was still a screw on, all depends on the quality of work of the last person in there
07-17-2017, 03:02 PM
#19
Chronic Tool Dropper
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Some of the conversion adapters end up bending the pin of the original Schraeder valve when they are installed, so I just take the originals out and let the Schraeder valve in the adapter do the job. The original valves have buna seals in them that fail with R134a oils (POE or PAG) anyway, and often end up gumming up the valves. Best to get them out and be done. (Note that the pressure switch has a Schreader valve underneath that MUST be changed for a R134a-compatible valve. For S4+ cars, change the one under the pressure transducer too.)
There's a lot of stupid stuff that needs attention for a successful R134a conversion in the 928. None of it is really difficult, but it takes time and care to get everything done just right.
There's a lot of stupid stuff that needs attention for a successful R134a conversion in the 928. None of it is really difficult, but it takes time and care to get everything done just right.