can anybody walk me thru upgrading my AC to R134a. I have a 93 SC400.
Thanks!

 

Need to have your r12 drained at a certified location. I believe you then change the coolant oil and replace with oil included in a kit. Easiest with a kit. I have no idea on the Lexus though, I watched a friend change an S-10s over.

 

Easiest method is to buy a kit specific for your car. This should come with the correct nipple adapters to switch your R12 over to R134a specific nipples. It should also come with "green" o-rings designed NOT to leak against R134a as older "black" o-rings were never designed to seal the smaller R134a molecules. A correct changeover would entail switching the nipples, replacing all o-rings many ppl suggest a new expansion valve also and a good 30 minute vacuum of the system to remove all air and check for system leaks before refilling with new freon. Also refill should only be 80% R134a ( if i remember correctly ) as compared to the original R12 capacity. If your system isn't leaking/broken i suggest you NOT upgrade. R134a does not cool as well as R12.

Regards

 

Let me add that switching from R12 to R134a is a DOWNgrade!

 

Unless I missed it...I didn't see anything about refrigerant oil. The R12 oil is not compatible with 134 and vacuming the system will not remove the old oil. You would need to flush the sysem first.
This conversion is more hasle than its worth. Unless you have a major component failure (ie:compressor, evaporator) you're better off just re-using R12. If you have no leaks there is no reason the stuff shouldn't stay in there, therefore your not wasting $ on freon. This conversion can result in many more problems. R134 generally works with higher pressures (you'll most likely have to replace pressure switches) and that's why you'll end up with more leaks than you originally may have had to begin with.
Frankinaustin...dont do it, it's not worth the trouble

 

I'd love not to convert to r134a, but all the r12 leaked out and i don't know how to get more. I figured that replacing the o-rings was going to mandate a complete system rebuild anyway so I might as well just switch to r134a.

 

I would bring it to a good shop and find out where its leaking from first.

 

It's really cool, they inject a dye and you can see where the gas is coming out of.

steviej