AC problems

Our A/C unit decided to pump only warm air today. All iced up inside. Not the first time. What causes this, besides the fact that the unit is an old POS. Anything we can do to remedy this? It's starting to get warm here.

Usually low freon = ice

Get a manifold and check the pressures, you can pick one up from Harbor Freight.

"NEGRODAMUS SEZ...YOU HAVE LOTS OF CATS...." Or a dog? Just a guess.

Let the big chunk of ice melt off. Running the fan will help this process. CAREFULLY clean the coil. Change your filter more often and make sure it's seated well. Crap is probably getting past the filter and mucking up the coil.

Or low on Freon. I'm on a maintenance schedule with the AC guys. You should look into that. It's cheap.

I'm betting on dirty coil, especially if you have pets and/or don't change the filter as often as you should.

I vote low on Freon, but it would be a good idea to clean the coils. Also clean out the drip pan while you are in there.

Another low refrigerant vote here, although making sure the coil is clean won't hurt.

What's all iced up inside? If you are talking about the evaporator, then the problem is that the thermostat isn't cycling the system to prevent the freezing. Low refrigerant will NOT cause freezing of the evaporator coil. You can't get the system cold enough to freeze without a decent charge of refrigerant.

If you try to cool too large of an area with too small of an air conditioner, it can freeze up as well, especially if it's humid.

In reply to bravenrace:

Not correct. Low freon causes a low pressure problem in the evap coil (inside coil when in A/C mode, outside coil when in heat mode). The freon changes from liquid to gas too fast and causes to evap coil to freeze. It starts at the expansion valve and creeps down the coil until the whole thing is a block of ice. A fairly common problem in the humid south.

bravenrace wrote: Low refrigerant will NOT cause freezing of the evaporator coil. You can't get the system cold enough to freeze without a decent charge of refrigerant.

You are incorrect. In Florida, it will happen.

I am not saying that is the OPs problem, but 90% chance that is. Also a dirty coil is not going to help and it will cause it to freeze quicker.

J

Could also be a bad expansion valve. Home unit or car?

bravenrace wrote: What's all iced up inside? If you are talking about the evaporator, then the problem is that the thermostat isn't cycling the system to prevent the freezing. Low refrigerant will NOT cause freezing of the evaporator coil. You can't get the system cold enough to freeze without a decent charge of refrigerant.

Um. What???

Slippery wrote:

bravenrace wrote: Low refrigerant will NOT cause freezing of the evaporator coil. You can't get the system cold enough to freeze without a decent charge of refrigerant.

You are incorrect. In Florida, it will happen. I am not saying that is the OPs problem, but 90% chance that is. Also a dirty coil is not going to help and it will cause it to freeze quicker. J

I hate to have to qualify myself, but I've been designing and testing mobile a/c systems for 20 years. I'm not wrong.

Toyman01 wrote: In reply to bravenrace: Not correct. Low freon causes a low pressure problem in the evap coil (inside coil when in A/C mode, outside coil when in heat mode). The freon changes from liquid to gas too fast and causes to evap coil to freeze. It starts at the expansion valve and creeps down the coil until the whole thing is a block of ice. A fairly common problem in the humid south.

If that's happening, the cause is a faulty thermostat or low pressure switch, or a really poor design, not low refrigerant. IOW, the low refrigerant freezing the coil is a symptom, not a cause. But your understanding isn't surprising since you don't know the difference between Freon and refrigerant.

bravenrace wrote:

Toyman01 wrote: In reply to bravenrace: Not correct. Low freon causes a low pressure problem in the evap coil (inside coil when in A/C mode, outside coil when in heat mode). The freon changes from liquid to gas too fast and causes to evap coil to freeze. It starts at the expansion valve and creeps down the coil until the whole thing is a block of ice. A fairly common problem in the humid south.

If that's happening, the cause is a faulty thermostat or low pressure switch, or a really poor design, not low refrigerant. But your understanding isn't surprising since you don't know the difference between Freon and refrigerant.

Whats the difference between Freon vs refrigerant?

In reply to Slippery:

Well, I actually may have mistated that, since I don't know what car he's talking about. I was assuming it is a 134A system. Freon is Dupont's brand name for R-12 refrigerant. It doesn't apply in any way to R-134A..

bravenrace wrote: In reply to Slippery: Well, I actually may have mistated that, since I don't know what car he's talking about. I was assuming it is a 134A system. Freon is Dupont's brand name for R-12 refrigerant. It doesn't apply in any way to R-134A..

Well, I'm no expert or anything, but I would assume from the wording that he's not talking about a car.

So Freon is refrigerant then ... Just a Dupont trademark.

Same as how Teflon is a Dupont trademark and the generic stuff is PTFE.

I would say that judging by what Toyman wrote, we cannot state whether he knows or does not know the difference.

J

It is a house system, and we have three dogs inside. Older unit, at least 20 YO. How do you clean the coils? This is a rental, we will be moving in a few months, so don't want to spend big bucks on it. Per the lease, we are responsible for cleaning AC coils.

Rental house or rental car?

Joking. Do you have pets??? (Seriously)

Assuming your indoor unit looks something like this:

Pull the access panel. The underside of the coil is what will collect most of the E36 M3 as the air blows through. When we had a billion cats, ours would need to be cleaned about once a year.

If you're lucky, the coil will look something like this (remove the bolts on the front to access the underside of the coil.)

If you're UNLUCKY (me) the lines for the coil are snaked all around the front of the damned thing, and a freaking nightmare to work around. Best tool I found for getting the cat hair out of mine was a straightened piece of wire hanger with about a 1/4" turned up on the end. I could get it off in pretty big sheets that way.

BE EXTREMELY CAREFUL NOT TO DAMAGE THE LINES OR THE COIL ITSELF.

Might as well go outside and clean the condenser coil. They make a spray solution for that. I DON'T THINK you want to use that stuff on the evap coil. Check the can. They sell it at Home Despot.

Regardless, if it was me, I'd pay somebody $80 (at least that's what my guys charge) to come out and do a general inspection, check the freon level, check for leaks, etc. Freon (refrigerant, whatever the berkeley) will more often than not leak from the lines at the evap coil (according to our AC guy anyway.)

Hopefully it's just the coil, as that's a pretty chicken E36 M3 fix. Hell, hang out with them and let THEM pull the panel and see if the thing is covered in E36 M3. THEN ask how much THEY'D charge to clean it, and micro-manage 'em to make sure it's CLEAN.

My $.02. Hope that helps.

Apparently there is a cleaner that's safe for indoor use(?)

http://www.youtube.com/watch?v=lTvKXOvWcxU

Yeah, I have used that cleaner. I would give it a shot yourself, otherwise call someone.

*note: Unless you enjoy cursing and throwing E36 M3, do not drop brush into blower

Well, access to the coils required our best Chinese acrobat imitation, bringing back memories of under dash electrical adventures. Used a brush and a shop vac. There was quite a bit of crud up there, but we got most of it out. A/C works much better now, actually blowing cold. Thanks for the advise, guys.

On the subject of low refrigerant causing evaporator icing:

http://www.hvacoracle.com/service/ac/evap_freeze.shtml

It's been known to happen in automotive HVAC as well. Typically it's a stinking hot humid day, the charge is a little low, the car is driven at highway speeds with the system set to 'recirc'. Mercedes has an evap temp sensor installed for just this purpose, it kills the compressor if the evap temp drops too low.

bravenrace wrote: I hate to have to qualify myself, but I've been designing and testing mobile a/c systems for 20 years. I'm not wrong.