Air Conditioner Question

[JohnHaggerty]

I had the AC condenser replaced as part of an accident. Now that I need the AC it is not blowing cold (not even a trace). I assume that somehow the refridgent leaked. I assume only the two fittings at the condenser were affected by the repair. After further tightening them, is it as easy as just adding refridgidant?

Thanks!

 

[mwilson]

How long ago was it replaced?? Did it ever work properly after the collision repair???

 

[JohnHaggerty]

After collision it still worked fine but the condenser was damaged but still sealed.

Replaced about 6 months ago. Living where it's cold, I don't know since I never checked it until now.

 

[mwilson]

You really should have it put under vacuum to see if you have stopped the leak by tightening the fittings. If it passes the test fill 'er up.

If you take it somewhere and tell them to vacuum only, and then recharge the fee should not be too bad. I am stressing the vacuum for two reasons, the first to check for system integrity and the second to remove any moisture from the system where it has been empty for a while. The moisture will boil off under vacuum.

Mike.

 

[Tuesdak]

Was the desiccant (part of the accumulator) replaced as well? If you find the system is leaking the desiccant is likely saturated - vacuum won't fix this condition. Say you put gauges on it and get 0 PSI. Even with pressure on the gauges this system can pull a vacuum on the evaporator during AC operation with a low charge and moisture can leak in. The PAG oil and moisture turn to acid and corrode the evaporator. Ice can block the orface tube causing the AC to randomly quit working.

To properly do AC work you need to charge the system by weight. This is a full vacuum and then charge the system. Everything else like topping off is a guess risking oil starvation (specifically failure and a debris mess in the system) to the compressor from low charge or bad performance from overcharge.

Unless you have AC recovery equipment... Have a shop pull the system down. (Some people in Arizona have this in their home garage simply as part of their normal tool set.)
Rent a vacuum pump and AC gauge set if you don't already have one.
Replace parts as needed adding oil as required per component replacement.
Pull a hard 30 min vacuum. Fix leaks as necessary. This removes free water in the system.
Replace desiccant, aka the accumulator. (Note AC oil is required to change this part including measuring the old oil from it.) Do not do this before pulling a vacuum as water in the system can ruin a new desiccant.
Pull vacuum and make sure it holds.
Charge system by weight. (A shop can do this for you.)
Note cans are 12oz and a pound is 16 oz. A scale is required if your system charge isn't some magic number that 16 oz and 12 oz cans can come up to.

Due to equipment cost recovery and charging is best done by a shop. This is all you need to pay a shop for unless the needed repairs are cheap enough to just have them do it all.

If you have any leaks a leak checker can help, but, again rent the experience of a good AC shop. Oily looking connections indicate a leak, but, the AC oil washes off easily with any water.

 

[mwilson]

All good information above.

I just learned that a bad compressor seal will eventually take out the clutch. Leaking R134A will wash the grease right out of the bearing...

 

[JohnHaggerty]

OK so it seems like just charging it myself is not the way to go. I'll consider my own Walmart can on top (after tightening the two condenser nuts) of what was probably an empty system a short term Band-aid (although it now blows cold).

 

[RVTRKN]

Good info, except unit can not pull a vacuum unless the low pressure safety/cycle switch is defective. Also if you have slight pressure left in system or out of refrigerant, take a heat lamp to the accumaltor while pulling a deep vacuum (500 micron or less) for 24hrs and that will dry out desicant and oil, if moisture is present. Of coarse after leak is fixed.

 

[Tuesdak]

Good info, except unit can not pull a vacuum unless the low pressure safety/cycle switch is defective. Also if you have slight pressure left in system or out of refrigerant, take a heat lamp to the accumaltor while pulling a deep vacuum (500 micron or less) for 24hrs and that will dry out desicant and oil, if moisture is present. Of coarse after leak is fixed.

GM systems only use a switch for sure and this is what I know inside and out. (Unreliable switch that is.) As I understand it the 3rd Gen Dodge uses a resistor to sense evaporator temperature to cycle the clutch. (Some years are updated resistors and locations due to icing the evaporator up.) So if there is a low charge cut out switch I am not aware of it and if there isn't a pressure switch the system can run in a vacuum. I'd be interested in where it's located if there is a pressure switch on the low side. Maybe some years didn't have one?

I do know a sign of a low charge for the 3rd Gen is uneven temps from the driver side vents vs the passenger side vents. The passenger side will be warmer with a low charge and you can feel it.

You need heat to dry out the desiccant (vacuum alone won't do it.) and depending on what kind it is the refrigerant oil will turn into something else nasty. For example:
Molecular Sieve is put in a furnace at 600 Degrees Fahrenheit for 6 hours.
Silica gel is done somewhere under 200 degrees for 24 hours. (This would not work with under-hood temps so NOT used for automotive AC.)
Bentonite clay is heated at about 400 degrees Fahrenheit for 12 hours.

Generally not worth the trouble and risk the bag will come apart letting the desiccant circulate through the system. Never mind the meltdown if there are any plastic parts or screens in the thing.