You should be purging the lines each time you connect a manifold set, not enough gas or oil remains after to be a contamination concern, but one can always keep an extra set of hoses to swap out.

I use my manifold with both R12 and R134a, have no issues with vehicles going as far as 250k+ so far.

 

https://www.f150gen14.com/forum/atta...089-pdf.47737/

 

So this morning it was 75. It did cool but at this temp I'm used to having to turn it down or add a little heat to keep it from getting cold in the cab.

It seems to help if I keep it on MAX until it starts to cool down. Then leave it on Recirc for a little while to allow the evaporator to cool down. Then I can turn off Recirc and turn down the fan. Seems to cool better. I prefer to only have Recirc off to have fresh air in the cab.

I have a 1K round trip next week and I'll be due for a tire rotation. I'll have it checked then. I've already checked with my shop and they do R1234yf