A/C Catastrophe
August 30, 2006 1:24 PM   Subscribe

We have a Chrysler Airtemp A/C unit (more than 20 years old) that's gone on the fritz 2 days before we're scheduled to be away for 2 weeks. Although it's in the 80's outside, about 6 inches of frost has formed on the rubber-insulated tube next to the outside unit. There's condensation all along the line that runs through the basement to unit where the fan and the copper tubing are located. The latter is also covered with frost but is now melting since I've turned things off at thermostat. The fan will only work if it's set to manual. I've called a repairman and he's suppose to come tomorrow. In the meantime is there any way for me to determine on my own if this is a catastrophic breakdown that will require a new unit or if it's possible for me to do something on my own to get the thing going?
posted by NinaLee to Home & Garden (5 answers total)
Could it be just a very dirty filter that needs to be replaced?
posted by jclovebrew at 1:38 PM on August 30, 2006

Mine froze up like that when most of the coolant had leaked out. It also behaved kind of like that when I had electrical issues in the inside unit, which was substantially more expensive (~$600ish) than just having coolant refilled ($200 with weekend service charges).

A dirty filter inside won't make the outside unit freeze up like that (though it might cause electrical problems on the inside unit that cost $600+ to repair), though dirt and debris in the fan part of out outside unit can cause problems that might do it.
posted by Lyn Never at 1:57 PM on August 30, 2006

Extreme icing is caused by
  1. dirty evaporator coil
  2. insufficient air flow over the coil because of plenum leaks or plugged filter
  3. low refrigerant
  4. weak compressor
  5. defective thermostat stuck on
  6. defective TX valve or TX valve sensor not connected properly
  7. plugged evaporator drain causing ice build up
1,2 and 7 are the only thing you could do anything about.

For 7 make sure the melting ice is causing water to come out your coil drain. The drain will empty into either a bucket or a floor drain usually.

1 shouldn't be a problem if you've been changing your filter every 3 months. If you haven't you could try taking a look at the coils to see if there is a build up of hair and fluff on the coil on the upstream side. Often the coil is not easily accessible.

For 2 first change your furnace filter then check around the plenum between the fan and the coil. If there are any gaps they need to be sealed up. Use a self adhesive aluminium metal tape available at the nearest Borg. The tape should be ~$1-2 per foot.
posted by Mitheral at 2:07 PM on August 30, 2006

The ice means the AC has frozen up. Most commonly, you see it when the temp drops below 70 and the AC unit is still on. Not in this case, I'd guess. Could be anything from the coils not getting enough airflow to the refrigerant being low.

Keep it shut off until the AC guy gets there. Running it, even after it thaws, could only do more damage.

I would bet the tech almost immediately suggests you replace it and offer to sell you one. A unit that old may be too costly to repair, the Freon would be impossible to get and the unit isn't energy efficient. The (US) government recently passed a mandate about minimum SEER ratings allowed (12) for energy efficiency.

If you do decide to replace, shop around. We recently dealt with this and were astonished by the variation on what different techs wanted to replace (anything from the condenser unit to the entire system in the house), labor costs and prices.
posted by jerseygirl at 2:13 PM on August 30, 2006

Mine recently did what you describe. It needed more freon. Worked like a charm.
posted by kc0dxh at 2:47 PM on August 30, 2006

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