Rhys

My 84 has the same issue on the same side. Thanks for the photos of a job well done!

My 84 was converted to 134a and now does not work anymore. It actually never worked well with the 134a anyway. I will have to change the Evap Valve now. It's located in the console and looks a bit involved. R-12 is still available, albeit expensive. But, it cools better and is what our systems are designed for. Are you really sure you want to change it out?

This was a common problem on Chevy PickUps. It is possibly the module in the distributor. Cheap easy fix to try.