Last year, I filled my AC system up with a can of R134A without changing anything....even left the old R12 that was in the system. I was in bad need of AC. Well.....it worked all summer fine. Now...the new summer has began and I am blowing warm. What I dont understand....the comp is working....the condenser is getting hot as hell....but the elec fan is not kicking on at all. The system still has a charge. I tried putting another can of R134 in tonight...and nothing would go in. I also have rear air....and its not getting cold....so I know it not a mixing flap. Any ideas? I do have a new drier, o rings, and expansion valves....I was hoping to by a few more weeks before I do the complete system refresh and re-charge. What would cause the compressor to run and the condensor to get hot and blow NO cold air?

Thanks

PS. I know....go ahead and do the refresh!!... I am looking for more input.

 

A properly charged system has a prescribed mixture of lubricant and refrigerant, which both flow thru the system together in a mixture. The R12 lubricants are not compatible with R134a. Similarly, R134a lubricants are not compatible with R12. The result is excessive wear to the system from inadequate lubrication.

Low on refrigerant is likely the cause of no or little cooling. Your pumping lubricant thru the system which transfers heat to the condensor. The compressor has to work to move the lubricant, which causes the heat buildup.

borland
90' S4

 

"Even" You say that like it is a good thing. That tells me you are now going to pay to have the whole system replaced. Plenty here on that no-no.

If OEM, you have permeable hoses, micro holes prevent damage from high pressure. Mine went 15 years before needing a boost, this is normal. Assuming the original problem was only the normal dissipation and not a leak, you would have been fine if you didn't mix 134. Do not release the remaining R12 into the atmosphere. You could try vacuuming it for 30 minutes, shut down and see if the vacuum holds, then probably no leak; replace dryer and all o-rings, recharge and hope. But you have probably damaged the o-rings with the 134 and you would be wasting time and $$. Start over with a licensed tech and new everything.

 

As SteveG points out, having a mixture in there is a disaster when you go to a place to get the old stuff recovered.

Back to your problem now: The mineral oil lubricant used with R-12 turns to jelly when you try it with R-134a. The mineral oil doesn't get carried around the system, and ends up in low spaces and where there are restrictions. The 'low spaces' will be the bottom of the condenser, evaporator, dryer and compressor. The dryere is going to be replaced, the compressor will be out to change the o-rings and drain the old oil out. The condenser and evaporator can be flushed, but you may or may not need that. As far as restrictions, there's that pesky expansion valve that probably has a bit of oil slime plugging it. This is a likely cause of your no-cool, and is a big risk to the life of the compressor. Don't run the AC until you get this straightened out, or you will find yourself at the compressor store at best. You can prove this with a set of refrigeration gauges.


What to do:

-- Recover the old refrigerant in a legal and environmentally sensitive manner.

-- Replace the o-rings at all the connections so that they will be compatibility with the new oil.

-- Drop the compressor, and flush it by hand with the new oil. Use the POE (Poly Olester) oil to flush the compressor, filling it with 8 ounces or so, rotate the compressor by hand to circulate the new oil and grab the oild oil before draining it out. Do this several times, then put a new dose of polyolester oil in the compressor before remounting it with the hoses attached.

-- Purchase a new pressure switch, the low/high cutoff kind used on the later cars. R-134a has a habit getting really big when it gets too hot, so the system pressures can get out of hand during a hot low-speed traffic situation. Use the right switch to protect your system from this excess pressure.

-- Replace the drier after you put in the new expansion valve. You'd ideally do the drier last, just before you put the vacuum pump on there to draw any remaining moisture out of the system.

-- Rewire your electric fan circuit so that the fan runs whenever the comnpressor is engaged. Leave the other stuff like th temp swict hooked up to it too.

-- Vacuum the system overnight if you can, with a pump that pulls a real vacuum. Many folks try to get by with cheap pumps that may only pump 29" or worse (at sea level...) then wonder why they only see vent temps in the 50 degree range. A good pump will do a lot better, and will get more moisture out when you leave it on the car longer. AC shop will try to tell you that 45 mins is enough. It isn't.

-- Charge the system a bit light, maybe 10% undercharged by weight compared with R-12. You'll get the most cooling with a system that just barely condenses at the expansion valve. Keeps the compressor head pressure as low as possible, which keeps the compressor suction pressure as low as possible, which translates into "coldest". It also gives you a little headroom when you get to stalled traffic before the high-pressure switch shuts the system down during that hot-soak.

-- Make Sure that your belt-driven cooling fan is working properly.


Good luck!