I'm having issues with my AC. Basically, the symptom is that I feel cold air coming out of the vent, but it has no pressure, almost like I have to put my hand IN THE VENT COVER to feel any cold air. To me, it seems like the blower is not blowing any air, or it's clogged somewhere in the process and it is blowing.

Just some background... I just moved into this house, so I don't know too much history of the AC here. We haven't really tried it yet because the weather just got hot.

It's a central unit with the compressor/condenser outside.

I found the filter inside was extremely dirty, probably due to all the remodeling we did here. I will replace that. (Note: as of this question writing, I have not tried the AC with a new filter yet).

My thermostat is new (On a side note in case of relevance, the previous thermostat did utilize the B wire. I did some research and this is a common wire, the new Honeywell thermostat does NOT have a slot for it, and the instructions state to tape it up and move it out of the way).

Continuing on in my troubleshooting, I have identified the Condenser coils are extremely dirty with weeds and grass. I have also identified the blower fan is full of dirt and dust.

I have a few questions which would really help me in continuing troubleshooting.

1) Can the condenser fins be washed with a garden hose after sprayed down with condenser cleaner? I have read different opinions online regarding this matter (I have seen some units where the fins/coils seem to come off the unit, and others where people spray the unit with them attached). I don't know what kind I have. It seems kind of sketch to wash the unit with a hose when there is electrical components inside. I'm a huge fan of the shop vac in case I can use that on the fins, as well.

2) Here is a picture of my blower fan. Can I take my shop vac/compressed air to this bad boy without damaging it? I don't know a lot about HVAC, brand new to all this. I am asking so I don't damage it further.

EDIT (Removed the pics to my dirty blower, thanks for the answer).

06/23 EDIT:

@Ryan Smith -- I looked up the Model number I found on the evaporator box above the furnace.

While I didn't find an exact match, I found the newest models have only 4 screws holding the cover on.

Newest model:


Here is my setup:


As you can see, I have some kind of tape covering my cover screws.

Looks like my top line can just pull out (Looks like a fit plug that pops out), and the bottom unscrewed... and I can check out how clean/dirty the evaporator coils are.

I don't know how (And don't have the tools) to do a test from the supply side, but I think there's still a benefit in being able to take this box off in that I can clean the coils off. Agreed?

Also, you told me to check out my ducting in the crawl space (I have a ranch style, so nothing HVAC in the attic) for leaks. I didn't even have to go that far. There's a hole in the duct right above the evaporator box. I posted a pic of it in a comment below.

Based on what I've seen so far, I'm not going to be surprised if the rest of the duct has holes all through-out... plus dirty evaporation coils.

Thanks for the help.

  • You can clean the condensing unit coils with a hose, just be gentle. I know it seems odd sense there's electrical devices in it. I'm guessing it rains where you live, so the unit has been wet before.
    – Tester101
    Jun 22, 2015 at 19:38
  • Thank you sir. And the blower fan?
    – amalik
    Jun 22, 2015 at 19:48
  • The condensing unit being dirty, will not reduce indoor air flow. Condenser cleaner is likely not required, unless the coils are really nasty. Yes you should be able to carefully clean out the squirrel cafe with a vacuum.
    – Tester101
    Jun 22, 2015 at 21:09

3 Answers 3


You had (maybe sub-optimal) working air, so the holes (unless new) are probably not the primary cause. I imagine your evaporator coil (the coil inside the interior air handling unit) has frozen over.

This typically happens when the airflow over it is restricted, but it can happen when the refrigerant has leaked out of the system. Air restriction prevents warm air from heating the coil, which will eventually freeze the humidity out of the air creating an insulating block of ice. Low refrigerant levels super cool the coil creating the same freezing over.

So, replace (or temporarily remove) the dirty air filter. Open all the vents. Turn your AC off for a long enough period of time to melt the ice (typically 4 to 5 hours, but sometimes less). Then turn the unit on. If airflow is restored, you know the symptom of your problem.

If you don't freeze up again, it was likely an airflow problem you just fixed with the new air filter and by opening the vents. Occasionally the interior fan is not turning on, so opening the interior unit is a good idea for visual inspection.

If air handling seems fine and it freezes up again, call a professional to find the leak in your system, have the leak repaired and then get your system recharged with refrigerant. Many pros like to charge the system and run; but, refrigerant doesn't degrade or get "used up". If you're low, there's a leak. Get them to find and fix it now or risk calls and extra strain on your system (which could shorten the life of your system).

Opening the unit involves removing the tape around the panel (it is typically metal duct work tape, so use gloves to avoid cutting your hands). The tape only seals the unit for air tightness. There are screws on the panel. When done, re-tape with metal tape for air tightness.

Keep in mind that the root cause is sometimes electrical. If so, you'll notice the interior fan not is not turning on. There are additional circuit breakers on the air handling unit, as well as the possibility of burnt out control circuitry, corroded / disconnected wiring, etc. It is a good idea to turn the breakers off and on just to assure it's not the cause.

I'd fix the duct work, but to save you money on your AC bill, it's not a likely root cause.


As Tester101 has already answered in the comments, yes you can clean the condenser with the hose. Unless the fin stock is in very bad shape, you should be fine to spray it down with water--you can even safely spray it while the unit is running, provided it was wired correctly. You can test the condenser fins by gently running your fingernail along the fins: if they fall off, they are in bad shape; be ready to replace the unit. If they just bend a little, they are fine. Visible loss of fin stock is also bad.

Although your blower is dirty, the reason you have poor circulation is more likely because of leaky duct work. Depending on how the unit was treated, you may pick up some airflow by (carefully) cleaning the evaporator/having it cleaned, but typical duct work in homes start out leaky and get worse with age.

Check your attic/crawl space for leaks in the duct work. Use the appropriate sealer or replace it as needed. If you can easily open the plenum on the supply side of the evaporator, you can confirm that you have good volumetric flow at the unit; given that you have poor flow at the diffusers, this condition would indicate bad duct work. If you have poor flow at the unit, check to make sure the unit is wired correctly for the right speed under cooling operation.

  • @amalik Can you check your links? I get 403 Forbidden for the Dropbox pictures.
    – Ryan Smith
    Jun 25, 2015 at 22:08
  • should be fixed above, and heres the other pic dropbox.com/s/0vdoxxtjgnbxt0s/…
    – amalik
    Jun 26, 2015 at 6:45
  • @amalik You should be able to get a good idea of how much air you are losing through the hole by feeling around. A hole in the duct work (especially one near the supply plenum) can create substantial losses. Do not try to remove the insulated and small line (suction and liquid refrigerant lines, respectively). If you have access to the return side of the unit, you may be able to clean it yourself, but having it removed and cleaned externally would work best. Edwin may also be correct - you can test by turning the fan on without cooling long after it was last on (so it can't be still frozen).
    – Ryan Smith
    Jun 27, 2015 at 5:35
  • @Tester101 or others, Is it OK to shut basement ceiling registers if I want more airflow upstairs? Or does it create harmful 'backflow' to the system and they should stay open?
    – amalik
    Jul 5, 2015 at 19:09
  • DO NOT touch the condenser fins. You could easily damage them, and/or they could slice you open. They are very delicate, and sharp like razors.
    – Tester101
    Aug 25, 2015 at 10:04

Dirty system can cause things to work a bit more sluggish. A common problem with AC compressors is a component called the start or run capacitor.

When your AC is called on by your thermostat your should be able to go outside and see if your compressor fan is turning. The compressor should also be running, it should sound like a bit like a fridge while its running, kind of like a grunt. When the pressure builds enough you should also be able to hear the refrigerant flowing through the lines. It might have a little hiss to it.

If none of these things happen after the call for AC is made, it is most likely your run capacitor that is bad. Another check, if the compressor fan isn't turning, is to give it a little push with a stick and it should start turning and pick up speed. If this happens, it is most definitely your capacitor.

Capacitors are cheap and easy to replace, but I stress they can be dangerous if you don't know what you are doing. So be careful or have someone capable of replacing one do it.

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