Replace R1234yf with R134a in automotive AC?

[Swedal]

I know you are not suppose to do it but how good or bad will R134a work in a car AC made for R1234yf? Can you simply drop it in or do you need to change oil and flush the system? And yes once again, I know its probalby illegal and I will burst the planet into flames by doing so bla bla....just want to know how it will preform in theory. Would never try it of course.

[Brian_UK]

Compare the PT tables for both refrigerants and the oil requirements, should give you a good start to your theory.

[charlie patt]

Well the only thing I can tell you is the comps run to hot on 134a I'm pressumeing they ain't getting enough sub cooling but comps run hot and on the good systems the sensors go mad shutting down the ac ECU because the sensors read erratic on 134 compared to yf on mercs and bmw and Volvo's they shut down as sensing they are short of gas because of out of parameters sensors

[Swedal]

Well the only thing I can tell you is the comps run to hot on 134a I'm pressumeing they ain't getting enough sub cooling but comps run hot and on the good systems the sensors go mad shutting down the ac ECU because the sensors read erratic on 134 compared to yf on mercs and bmw and Volvo's they shut down as sensing they are short of gas because of out of parameters sensors

Very good info, thanks. Then R134a is a no go in these systems. Or maybe try running it abit under charged? What about a HC mix with 600 and 290? That should run cooler right? Not meant for using in a customers car of course.

[charlie patt]

I would never run a 600 290 hydrocarbon in a vehicle unless designed for it just use what's it's designed for

[coolguy4]

134a works great in 1234YF systems, my buddy did that and his system works perfectly, he said it actually cools a little faster and works a little better at idle. 1234YF doesn't carry oil as well as 134a so it needs a special oil. 1234YF oil works with 134a because its more soluble but not the other way around. Here's a PT chart comparing the two, the pressures are very similar.
pt curve.jpg

[Swedal]

I tried it now in a Peugeot 308 and it seems to work great so far. Pressures/temps look good and I dont seem to get higher dischage temp either. I run it a bit less R134a than R1234yf charge but seems to cool just as good or slightly better now. Will run it during this summer and keep an eye on everything.

[coolguy4]

I tried it now in a Peugeot 308 and it seems to work great so far. Pressures/temps look good and I dont seem to get higher dischage temp either. I run it a bit less R134a than R1234yf charge but seems to cool just as good or slightly better now. Will run it during this summer and keep an eye on everything.

Wait I thought you would never try it! But in all seriousness I'm glad to hear that it's working well for you and I hope and expect that it will continue to work well. Be sure to let us know how it works on a very hot day, that's where I would expect the improved performance to show the most.