I have a 77 f100 custom with a 302. I bought a A/C system form someone on Ebay for $400. After some cutting and replacing the dash, I got the unit in. This is a Factory A/C system and the seller included a template for cutting the firewall. I was cheap originally and just put the thing in. The blower motor was not the best and the heater coil started to leak. Back to step 1. I replaced the heater coil, blower motor, expansion valve (134a specific) all the o rings with the green ones, drained the compressor and put in the oil for 134a, replaced the dryer with one for 134a and pulled a vacuum. The vacuum held all winter so I broke it with 134 and then puled a vacuum again. I put in about 28 oz of 134a Quest Subzero from Autozone. At 85 outside the sight glass shows about 1/3 bubbles and 43 on suction (know 134a operates at a higher psi so i wanted to leave some room) and I have 56 at the vents. I was shocked at the temp. I was going to be happy with a temp below 70 with 134. Just wanted to let everyone know that there was a light at the end of the tunnel if you are adding A/C or converting to 134a. Just pay atention and do everthing right.

 

I'm about to start gathering parts for this. My truck has factory A/C already but I took out the condensor, dryer, and evaporator core. I have a new heater core and my blower works fine. I posted the other day about finding an evaporator core in the JY, but buying the other components new. In your post you say you bought a 134a specific expansion valve and dryer. Where did you get them from and did you just ask for 134a compatible parts? Thanks,

 

All new accumulators and receiver/dryers have R134a compatible desiccant in them. A real parts store, like NAPA, can cross an R134a TXV from their catalog. Maybe rboeding will post the manufacturer and part # of his valve, then nearly any store can get a proper one.

rboeding,
Good Job. It sounds like you're still undercharged, though. There's no reason not to be seeing vent temps in the 40s on your truck. High 30s are possible with some modifications. You really need to be able to see the high side pressure before adding any more refrigerant. Also, make sure you have the right fan shroud and a good (new) fan clutch if equipped.

R134a ring at a higher High side pressure than R12 in a converted system. The Low side pressure should actually be lower.
If you put a proper manuifold gauge on it, i'll bet you can get better vent temps.

The only thing you did wrong was using that crap from Auto Zone. You just got owned by slick marketing and a flashy package. The magic juice in that can will do absolutely 0 to help your system cool better and actually is a contaminant in the system.The gauges on those cans are often horribly inaccurate too.

 

Thanks, lsrx101. I plan on trying to run out the JY tomorrow morning and look around. On my price list I have they sell evaporators for $16! I hope I can find a good one. I'm sure I can, they have a few 73-79s.

 

My son told me today that the conversion to 134 is about $50. Is that true or is he delusional?

 

Not delusional, just misinformed.
There are "conversion kits" available at the chain parts stores and Wal Mart that allow you to add R134a and some Ester oil to an R12 system to make the AC system "work", somewhat. They were $35 for many years, but the price has gone up recently. They are now about $45-50. They are known by repair professionals as "Death Kits".
Sometimes those kits work as expected, depending on the original condition of the system, the type of system and other factors. The success rate is about 20%.
Most often the results are less than optimal, often resulting in compressor failure and major repair expense afterward.
They are widely regarded as "snake oil", much like additive engine traetments, stop leak products and other "repair in a can" products.

You can perform an R134a conversion, properly, for about $300 DIY if you have access to a few specific tools. If a retail shop quotes you a figure close to that, decline quickly. Retail, a proper R134a conversion will be in the neghborhood of $600. (darn close to repairing the system and staying with R12).