I orginally posted this question in the 73-79 forums, dunno why I didn't try here first.

Ok, so had A/C evactuated and charged beginning of summer, it's factory a/c in a 78 w/400.

Worked decent for a few days, then it stopped working. Added some r12 (guy that did it didn't follow the 2% rule ) and I knew then why they only charged $20 to evacuate and charge it. Added until the the bubbles just cleared, and it got colder. Worked for about 5 minutes, then I noticed the line coming off the top of the accumulator/drier was condensating. So now, it will cool for about 5 minutes after start up, then the top line of the accumulator/drier condensates and cools, and the air gets warmer (obviously). So naturally I am assuming that there is a clog in it, causing a low pressure problem in the top side of it, am I assuming right?

I dont want to waste $35 on a part chasing a problem.

Also, would the system need to be flushed? I thought I read something at one time about some kind of material in accumulator that if it comes loose can clog and spread into the system?

One more thing if anyone can help out,

HEARD that one redneck way of pulling a vacuum is you can actually use the a/c compressor. After all, it essentially is a vacuum pump.




I got a few replies, here is the link and my response (its not long guys I promise!)

https://www.ford-trucks.com/forums/9...r-clogged.html

 

As mentioned, it sounds like the R/D is plugged qnd you have too much oil in the system.

What kind of oil was in the system to begin with? What kind did he add? Do you know what refrigerant he charged the system with for $20?

At this point you would be better off starting from scratch. Replace the R/D, clean the Expansion Valve inlet screen, solvent flush the rest of the system to remove the excess oil, drain and fill the compressor, then evacuate and recharge.

Forget about "hillbilly" methods if you want the AC to work and be reliable. If you do it right, you'll only do it once. Use a correct vacuum pump and manifold gauge set.

 

I dont know what kind of oil he used or what was in it. I supplied the r12, have a tank full of it.

How do I flush the system? What kind of solvent do I use? how extensive is the tear down to flush the system? I am not new to mechanics, but just started learning about a/c.

 

You need a fully evaporating solvent like Dura-141 AC Flush. Other solvents, like lacquer thinner or MEK "can" be used with proper precautions. You also need access to LOTS of DRY compressed air.
Remove all of the hoses and hard lines and flush each part separately, making sure all of the solvent has dried. The heat exchangers can be flushed in place. Once you think they are dry inside, blast them with air for a few more minutes. The evaporator is the trickiest part to get dry inside so, if in doubt blast it again

The compressor needs to be removed and drained through the oil plug on the side of the case. There are actually 2 plugs IIRC. Drain, add 8 ounces of oil, spin the compressor over about 20 times, drain again thoroughly, add the recommended amount of oil into the crankcase then reinstall the compressor. (Mineral oil for R12).

Install the R/D last and pull a vacuum as soon as possible after installing it.

It sounds like a lot of work, but you can do it all on a Saturday. Doing it this way assures a clean, dry system from the start.

Good Luck