Air conditioning

I can tell you this, they sell r12 to r134a conversion kits with complete instructions on how to use them. I do not anything about this tek12 or its compatibility or how it works. If it was my car I would just convert it to r134a.

A round here a product called "Freeze 12" was the solution to the need for R12 in older vehicles. Most people who are in need of the air conditioner in their older vehicles now bite the bullet and retrofit to use the R134a.

The one I mentioned and the one you mentioned (claim) it could be installed "on top of" the R12 without clearing the system of the old oil (more work)

I have a link to the one you questioned

https://www.amazon.com/RED-TEK-R12a-Refrigerant-Recharge/dp/B00DJDYORU

Their ad says it is compatible, I do see that they have adapters for the fill/ test ports so that the newer style hoses/ gauges can connect to the old style ports

Yep, I would give it a shot myself.

The Medic

I have never drained the old oil out when converting from r12 to r134a also the air is cold when your done.

I have never heard of it costing that much. They sell a diyer kit at the auto parts store. So your going to have it done at a shop?