A/C out, how can I tell if it was converted to R134?
 

A/C needs a recharge. How can I tell if the former meticulous owner converted it to R134? He is old and can't remember... Thanks.

Car is US Spec 1990 300D 2.5Turbo.

Look at the valves.
 

If they have the quick-connect fittings it was most likely converted.

Meek:

134a quick connect valves will only work with 134a hoses, etc.

Cary

The only way is with a refrigerant identifier. Most shops that do A/C work should have one (in CA it's mandated). To just identify shouldn't run more than 1/2 hour of labor.

The valve thing is a good quick glance type check, but can be misleading as folks can put R-134a in without changing the valves. R-134a is used in many applications, only automotive has the different fittings. A/C techs from other industries have gauge sets that will connect to standard fittings, without the unique automotive quick connects.

If it's empty you can vacuum and charge with the refrigerant of your choice, if it's not empty you really need to know what's in it, as no one would want to recover what it does have and risk contaminating their equipment with unknown or mixed refrigerants.

MV

How well did it work before? If it got nice and cold, it was probably R12.