DKWalser

Alan - I had not noticed that yet. When i do, I'll know what's going on. Thanks!

OTR18WHEELER

thanks

Rob Edwards

For whatever it's worth, here's the Factory TSB on r134a retrofits for 83-92 928's, which lists the part #'s for r134a hi/lo side valve adapters, driers, etc by year. Interesting the relatively low tightening torque on the adapters (~8 ft-lbs)..

https://webfiles.uci.edu/redwards/pu...%207-25-14.pdf

The Forgotten On

Would being undercharged 3 ounces of refrigerant cause poor performance? Because mine was filled with 1.7 lbs of R134 instead of ~1.9 (1.89 but close enough )

dr bob

It might under certain circumstances, but generally there's a bit of tolerance around the factory numbers. The system is extremely dynamic, in that it needs to provide cooling at varyin ambient conditions, cabin conditions, and engine speed. The holy grail of operation has just enough charge to barely keep liquid at the expansion valve. This provides the highest heat movement capacity and the lowest evaporator temps.

You can check the current condition by looking at the sight glass in the top of the drier. With fans set on the second position and engine speed above 1500 RPM, the sight glass should show a liquid stream with a few vapor bubbles. The refrigerant is clear when condensed, so watch for pale yellow streamers of oil as they are carried past the sight glass as a sign there's liquid flow. If it's mostly vapor, the flow is much faster and you may have a tough time seeing it. Charging to fill the sight glass is not ideal for R-134a systems, especially for conversions. Your early car has no overpressure protection from the factory, so a hot soak in slow traffic risks damage friom high-side overpressure if -anything- isn't working perfectly. Charging to the sight glass appearance tempts you to put in "just a little more" to "make sure the system cools under all conditions". It can be an express ticket to compressor damage, and is always a contributor to decreased performance.

SMTCapeCod

More on this please- "Nippondenso 10PA20c ", looks to be nicely priced, is there actually an uptick in performance/capacity of some sort?

Rob Edwards

Not sure why they went from the 6E171 to the 10PA20c, nor whether there is a performance difference between the two. The bracketry and hoses are very different between the two, so a swap between the '87-89 and '90-95 setups would be way more than just the compressor. Probably not worth the cost since the condenser capacity is usually the limiting factor in performance anyway.

The Forgotten On

Thanks dr bob.

CraigL

There was a change-over in US 1993 models.
The early '93s were R-12. The late ones were R-134a.
Apparently the early '93s were manufactured in 1992.