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Phil, Shop owner
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Experience:  Degree, Mech. engr. shop owner. 51 years experience
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Furnace is dripping when I turn the central AC on. Need help to fox th

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Maytag Central Air Conditioner/ Furnace Problem. When we run the AC (not often), the bottom of the furnace has water dripping into it and filling the black mesh at the base until it overflows. Model MGF 1RC080C12B.
The water is dripping through the hole for the alignment tabs that is above the circulating air blower assembly, then running off the round blower cover to the base where it leaks out. I removed the Induced draft blower and did not see any water in the Front Header Box. It appears as though the condensation should be draining through the tilted front header box to a condensate drain tube. Both the drain tube and header are clear/dry.
The AC does still cool the house and all motors are running when I over-ride the two cover switches and watch the process.
If I remove the horizontal sheet metal deck that separates the upper and lower units of the furnace (and the Circulating Blower with it) will I be able to see where the condensate attaches to the header box and maybe diagnose the problem? I removed the screws from the front header box but was unable to remove it. When I removed the induced draft blower, I could see inside the header and see steel tubes inside, but no condensate water. How does the condensate water get into the header box and out the drain? Is that what is actually what is supposed to be happening? Any repair guidance would be great.

Welcome to Just Answer !

We will be best off starting from scratch here and not getting involved with the header for now.

The cooling coil as you are aware, gets cold and water collects on it, and that drips into a collection pan mounted half an inch below the coil.... If the accumulation of dirt, mold and slime that builds up in the pan, the pan will over flow and run down the inside of the furnace....

First step is locate the point where the 2 copper refrigerant lines enter the coil box that is mounted above the furnace, and remove the entire front cover of the coil and inspect the drain pan.... Tell me what you find. We can go from there... There are other related problems we need to discuss depending on what you find.

If you have trouble finding that panel (20" x 20" approx.) send me some photo's of the area by using the paper clip icon.

Phil and other Appliance Specialists are ready to help you
Customer: replied 4 years ago.

Just got the sheet metal cover off in front of the coil. No fun. Sheet metal with Pittsburg bends, Plumber's putty around the copper pipe entries and drain that were cut to size then soldered. Not to mention the inlet and exhaust PVC 1/2" away from the cover. Some ugly cuts and bends later I got the cover out of the way. Whew!

Found what I think was a deteriorated mouse inside the drain hole to the outside of the unit from the pan. I'm not sure if it was enough to stop the flow of condensate, but it is not like that water is under pressure. I was also surprised that the drain pan was not full, only damp. Other than that the pan looked ok, slightly dirty at best.

Is there something else I should check? Should I try to clean the coils now that I have it opened up (and what is the best way to do that)? Does that header box do anything in general or is most of the condensate supposed to go out the drain tube by the coil?

Good work!

You can buy an 'AC coil cleaning kit ' at large hardware stores, it comes with half a gallon of coil cleaning solution, a special brush or 'comb' to scrape the dirt out from between the fins.. cleaning the coil is a very good idea.

Next we need to find where the water is going since the drain pan is dry.

Water could be 'spitting' from the coil due to high velocity caused by a dirty coil, or water could be running down the face of the coil and hitting some hair or built up dirt and finding its way around the drain pan.

The first thing to do is to pour a gallon of hot water with a quarter cup of chlorox in it, into the drain pan and see if any water leaks through any rusted out spots.

Let me know what you can find out.

(Before I forget, have a new coil cover door made by a sheet metal shop, ideally with 2" flanges on one or more sides to stiffen it up that will fit using 1/2" long sheet metal screws... ask them to use 'duct liner' to cover the inside, and then use 6 or 8 screws to hold it in place and seal the edges with duct tape...or better yet, duct caulking that comes in caulking gun tube.)

We can go from there with no time limit until we get the source of the water leak found and repaired.

Regarding the sloppy job with the copper tubes penetrating the sheet mental.. the sheet metal needs to be at least 1/8" away from the copper or it will corrode and a make the copper tube leak..

Customer: replied 4 years ago.

The pan under the coils is a thick plastic, so I doubt it leaked. I did pour in a gallon of hot water which did all drain properly down the line. I did not add the bleach for fears of having to clean it up if it leaked.

The local big-box does have an AC foam cleaner and a brush that they say will help straighten bent fins. The coil tower sits on the pan with a 1/4" channel to take water to the front and out the drain, pan maybe holds 1/2 gallon before full. The pan sits loose on top of the furnace, can I move it around to clean it or might I damage the copper / fins?

Since the unit does seem to be draining, should do the bleach rinse?

At this point I plan to clean the coils/fins and put it back together with some aluminum duct tape. The installers did leave a 1/2" gap between the sheet metal and copper, but they soldered a copper elbow just outside the opening. Do you suspect there may still be a leak? I am thinking the drain was plugged just enough to overflow the pan, yet allowed water to very slowly drain over the 15 hours since I last ran the unit.

After you respond I will run to the store and do the cleaning and any other instructions from you. The maybe I will test it out.

Goodman makes coils with thick plastic pans that tend to crack.. The cracks are not always apparent. We need to take our time and look for that. Goodman coils are less expensive and often used in place of the original equipment.

You can move the coil around and inch or two without any force and generally not do any damage...the tubing generally has that much flex in it.

I suspect a crack in the plastic where the copper tube adapter screws into the pan, or elsewhere in the pan.

Or a leak is in the pipe threads since the installers would have had to make the solder joint after the adapter was screwed into the pan... That heat could have caused a lot of problems (most drain lines are plastic, and screw into the plastic pan, and the fittings of course are plastic, and are glued). The refrigerant lines are copper, but do not even come near the drain pan. That should help clarify what the tubes are all about.

Regarding fin damage... They can be bent and that does not hurt them.. It is just better if they are straight.

You should not put it back together until you know you have found and fixed the leak.

Customer: replied 4 years ago.

Before reading your message I went to the store and purchased a foam coil cleaner that supposedly will release any dirt once the coils begin to condensate. I did go ahead and put the unit back together (maybe a mistake) and am currently running it to see if any leak occurs. No leak was apparent in the few gallons of hot water I poured (via yogurt container) into the drain pan. It would seem odd that a plastic pan would crack without impact, but I suppose it is possible. I will write more in a few minutes after I test it.

Aaack. It is still dripping down into the furnace from somewhere. Maybe it is a cracked pan, it is difficult to see much other than the front edge and as I wrote earlier there is no space under the coils, only two 1/4" channels to the front. A small trickle of water is coming steadily from the drain tube so at least some is draining and all the water I poured through before would have shown any plugs in the line.

How can I check the pan for cracks? Is there any other possible problem that may be happening? Can I run the unit with the coil section above the furnace open to watch it operate?

Thanks for your help and patience with this.

Possible leaks are:

- Plastic pan gets a stress crack and leaks... Its common with plastic drain pans.

- The female pipe threads on the pan crack when the male pipe thread fitting is screwed in too tight... Or the pipe dope used begins leaking over time (its a bad design in my view.)

- Dirt, hair and fibers form a pathway from the coil surface past the edge of the pan, usually at a back corner where you cant see it... and you get a few drips of water an hour leaking past the pan... Just two drips an hour for 8 hours a day, is 16 drips, enough to make a little puddle and ruin any electronics that it drips on.

- Just one drip a minute adds up to quart or so of water a day... These tiny drips can be very hard to locate.

Some of these tiny leaks only show up with the fan running and the access opening closed... Finding them can be a problem.

Solutions, start by cleaning the coil very completely especially around the corners.... Fill the pan with water by blocking the drain then use a mirror and a flash light to look for any dripping from the pan bottom or around the threaded drain connections.

Dry the bottom of the drain pan and drain fittings with a paper towel.. so its bone dry, then fill the pan, and wait half an hour... then use dry toilet paper to rub the bottom of the pan... any water will instantly dissolve the toilet paper... That works very well. You can locate water leaks that you cannot see that way.

Customer: replied 4 years ago.

Thanks, I will take the cover off again, plug the drain and fill and watch. The plastic right angle fitting does screw onto a port on the drain pan, with pipe dope. I did not see a leak there before, but maybe.

I am really beat and will go at this again tomorrow. It would be nice if it were the accessible drain port, not the unseen unknown. Tomorrow.

Yes indeed it would be good to these systems built with maintenance in mind. The dry paper towel and tissue approach will work the best in this case.

Customer: replied 4 years ago.

I really cannot see a way to dry out the pan since it seems attached to the bottom of the coil/fin unit. The coil unit weighs about 50lbs and I only seem able to lift the unit (with the drain pan attached) about 1" before it binds on the copper pipes.

I did plug the drain hole and fill with one yogurt container of water. It did immediately start to drip down through the furnace.

I am not sure how to proceed. I may need to cut the copper pipes and the furnace PVC inlet/outlet to remove the coil and drain pan and find the leak. Cutting the copper pipe would lose my freon, and while I have done some pipe soldering, I am not sure what is involved with doing that on refrigerant lines.

Again the coil unit and the drain pan are attached, with no gap to investigate the majority of the drain pan for leaks. Is there a way to lift the coil unit other than by the 1/4" recirculating pipes? I do not want to damage them.

Discouraged. Is it time for me to give up?

I hope you are not slapping your head with each new message from me.

Don't cut the refrigerant lines, evacuating the system then recharging requires equipment you probably don't have and may not help you find the leak.

If you call in a shop they will spend hours and possibly not find the leak either. Or they will cut the refrigerant lines and remove the coil and still not find the leak. Or they will re fit the drain lines and maybe get lucky.

Some shops will recommend replacing the entire coil and drain pan... That is a bullet proof solution... A new coil and drain pan wholesales for $350 or so. It takes one man at least 4 hours to change the coil, most shops will flat rate the job at 8 hours. and mark the new coil and drain pan up 50% or so. Some shops will order you a new drain pan if they can find an exact replacement. That would be the most cost effective solution.

The best solution would be a new *metal drain pan... These plastic ones are known leaker's especially the older ones. This is a 10 cent sized defect, with a thousand dollar solution.

You are not causing me to slap my head. This is all part of what it takes sometimes.

Customer: replied 4 years ago.

Could I lift up the existing pan/coil and place a new larger pan underneath and run the drain from it? I do not know if I can do that because of the PVC air intake/outlet at the front of the unit. Also where might I purchase a metal drain pan - plumbing shop or would Home Depot have this item? The unit would have be designed with the middle open for the air to flow through, yet surround the existing plastic tub. I would even be willing to try to make it out of sheet metal coated with some of the rubber spray sealers to save replacing a coil which seems to be working, let alone the labor cost!

You will be best off having the sheet metal shop come out and measure for a new pan... tell them you want it made of 20 gage galvanized sheet metal, spot welded and soldered...ask them to prepare the pan for paint. (they rinse it with acid) .. Then buy two cans of ZRC 95% pure zinc spray available at most Refrigeration and Air conditioning Parts Wholesalers, the sheet metal shop should be able to buy it for you.. Its expensive. It is a self healing pure zinc powder coating.

Tell them to make the new pan 1/2" to 1" deeper than the existing one if they think you cal lift the coil high enough to get it to fit..

Ask them to send their air conditioning repair service man to measure up the pan.
It will cost you $200 to $300 most likely.

That will outlast the rest of the system. If you do not use the ZRC it will last 10 years or longer.

It might be possible to find a metal pan for that coil... it would take a few hours of searching.

It would be easier to find a plastic drain pan for that coil, cost with shipping maybe $100.. I can see what i can find, I would need the coil model number and serial number from the name plate on the coil. Odds are in the 80% range that it would fit.

Regarding the plastic vents, if you can send a few pictures using the paper clip icon in this dialog box that will help.

Customer: replied 4 years ago.

AC Coil ac coilla/c drain panac Coils side view

I have attached photos. I can remove the large PVC pipe in the center with screw clamp, but will need to cut and reattach it with a coupling and glue, or maybe I'll use a rubber boot for future access.

The coil model # BV 132 30+X2 Z30LH and says "Refrigerant Evaporator" just above this (I do not know if this is a mfg name). Though my furnace/ac is labeled Maytag the system manual is from Nordyne.

The black foam colored pipe in the photo is the copper that runs into the coil from outside the furnace, as does the thinner copper pipe that is connected to the blue filter(?). I had to cut the sheet metal around both of these to have access to the coil.

If you can locate a plastic or metal unit that will fit under the existing unit without much trouble, I would appreciate that. The outside of the existing drain pan is 13"x19-1/2"with a drain hole 2-1/2" from the left edge (3/4" pipe nipple). The opening under the coil into the furnace is 9-1/2" wide by 19"deep and begins 1-1/2" from the cover door.

It will be difficult to get a new pan underneath. Any suggestions(?)

The pan attach's to the coil with 8 screws, two on each corner.. Getting to the two back corners can be done by disconnecting the duct that comes off of the top of the coil cabinet that the coil is in, and then removing the screws that hold the cabinet to the furnace... Then lifting the cabinet up so that you can reach the screws at the back of the coil that attach the coil to the pan. Not an easy job particularly if the furnace and that plenum are fit into a tight closet.

The pictures did not get past our server... Try sending those pics to '*****@******.***' attention 'alumalite'... I am sorry about that... Or you can post them at and send me the URL address to the pics.

I an not able to locate that furnace model number under either Nordyne or Maytag, but it seems you have a combination combustion air intake and exhaust in one arrangement... Its a double wall type arrangement, the inner pipe is 3 inches in diameter (its inside you cant see it is the exhaust tube,)

The outside is 6 inches in diameter approximately, and combustion air is drawn in through the gap between the inner and outer tube..Tell me if this is what you have or not.. That is most common if it is in the middle of the furnace. (the other option in these high efficiency furnaces is a 2 inch and a 3 inch plastic pipe, separated by a few inches.

You cannot easily cut the tube within a tube arrangement that you seem to be describing... It can be done but only by someone who works with the double wall arrangement and has the skills and parts.

I am not finding that coil number, it may be 'obsolete' next step is to call the parts vendor CLICK HERE I can call or you can, it will be better if you call since you will be better able to relate the pictures of the coil... Their 888 number is ***** page one of the web site... See what they know about that coil model number and replacement pans.

Let me know what they say, we can go from there.

Customer: replied 4 years ago.

I do have two PVC 2"pipes coming into the unit. One bells-out to a 3" rubber connection attached with screw clamps to the PVC. The other, less in the way on the right front stays 2" into the unit.

Removing the rear wall of the coil cabinet will be difficult, and lifting the coil unit up to remove screws next to impossible as it is next to a wall. Also those walls are like the front, sheet metal. Maybe I can get it.

If I can get the coil off the drain pan, should I just try and seal it? I thought before you were suggesting a pan to go around and under the existing unit. If I am removing the pan it seems as though you are talking replacement. Also if I get the screws out and remove the coil drain pan, how will I support the coil without damaging the coil/fins?

The original number I gave you was the Maytag Furnace model number. My previous letter was for the coil model number.

If you have two 2" pvc pipes you can undo the clamp on one, and fit a glue coupling in the other. It sounds like a tough job from here, you will have to put the screws back into the pan and coil connection.. That is going to be tough.

Don't worry about the fins... Too much, bending a few makes no real difference unless its in a place that will cause water to leak around the edge of the pan. From the sound it, you might be forced to replace the entire coil/ drain pan and coil cabinet as a set..that avoids having to deal with those inaccessible screws... talk to the nordyne vendor about the total cost of that... probably $390 for the coil and pan, and another $100 for the coil cabinet.

If you go that route however the systems refrigerant will have to be recovered, and the refrigerant lines will have to be cut... Then the system evacuated and recharged, that turns it into a $1,000++ job. This happens when equipment is installed in too tight a place to allow service.

Customer: replied 4 years ago.

I don't know if you received the photos. I think I will try to remove the coil case and then the pan. Hopefully I can seal/fix it. a more Monday). It frustrates me to buy a new coil when it seems to operate fine. Is leaving the existing drain pan in place and fabricating another pan to go around it with sheet metal a reasonable solution? Reasonable for a bricklayer with tin-snips?

Again, I appreciate your patience.

Nordyne sells the drain pan as a part. Given the extreme difficulty in replacing the pan it will pay you to do the dry paper towel and tissue approach to locate the leak... and super clean the coil and look for any possible way water from the face of the coil can run around the pan... Even a single hair can be used as a drip path.

Remember you are only looking for a leak as small as one or two drops an hour during the time the system is in cooling mode. It will pay to go to extremes to do that dry paper towel and tissue testing approach. Building another pan to go around the existing situation will be as much of a problem as any of the other approaches.... Just a different set of problems.

In the past I have always concentrated on finding the leak first... Then the remedy.

I got the pics... The first one shows the bottom of the coil fins possibly touching the sheet metal side of the coil casing... Water from the fins will be pulled onto the sheet metal by 'surface tension' and the water will run down the side of the coil casing.

The other thing I noticed is no insulation inside the coil casing.... If the cold air coming off of the coil is below 45F... The sheet metal on the coil casing will run at that temperature.... In humid climates that surface will collect condensate (like the outside of a cold soda can)... That condensate will drip down into the furnace. So that , the drain pan might not be the problem after all but one of these other issues.

Look that over and tell me what you find, use a thermometer to measure the temperature of the air coming off of the cooling coil... we can go from there. There is one other thing, that exhaust vent does not look right, it is reduced down from an apparent 4 inch vent.. Somehow I need to get a better model number on the furnace or find the installation manual to see what is up with that.

Customer: replied 4 years ago.

Thanks for continuing on with me on this. I am glad Nordyne sells the pan as a part. It looks to me that I can remove the side of the coil case with the humidifier and hopefully access from the front and side will be enough to lift the coil and replace the pan.

I am fairly sure there is a leak in the pan from when I did the test of plugging the drain tube and filling the pan with water. When I did that water immediately began dripping down through the furnace. I will check again for "bridging" sources, but I do think the pan is the problem.

I will try the paper towel/toilet paper test once I have the pan off the coil. With the two attached I do not have a way to dry out and test anything other than the front 1 inch of the pan. The rest is under the coil, attached to the pan with little gap.

I understand your concern about the uninsulated walls sweating. Since the pan itself leaked when I plugged the drain and filled it, that seems to be the problem. This test was done with the front wall open and the ac off for several hours, so I do not think wall condensation is an issue.

I am not sure why the installer necked down from the 4" opening to the 2" pipe, although most all furnace exhausts/intakes I have seen around here are 2".

I hope to remove the side case and then the pan from the coil. I sure wish there was a way to disconnect/reconnect the copper pipe and pull the whole unit, but I will see if I can get the pan out without disconnecting the refrigerant lines (which would lead to other issues). Once I have the pan off (wishful thinking!) I will look for cracks and test it per your technique.

I will be in touch after I do that work. Thanks

Good plan

A licensed condensing furnace technician needs to look that installation over.. these need to be set up and adjusted properly using instruments (flue gas analysis, and manometer.)

Customer: replied 4 years ago.

I loosen all the ceiling brackets supporting the copper refrigerant lines, then hoisted up the coil/drain pan with two 2x2s so I could try and get at the screws to separate the coil/pan. Instead I found a bracket clip of sheet metal that hooks on to a tab on the plastic drain pan. After a few tries I was able to disconnect the two, call my wife to help pull the drain pan out while I held up the coil, with a little bit of scraping across the fins, we did it!

The pan is cracked in two places. It also has some heat marks that have melted a few places on the bottom of the pan to a marshmallow brown. I can see why a metal pan is preferable.

It is too late today for me to call Nordyne or another parts place to locate the pan, and hopefully I can locate one in metal. If I cannot, I may try to repair the the existing pan leak with an epoxy that can withstand heat. Any thoughts? The cracks are clearly visible and I will test it out several times before the tricky task of putting it back under the coil. So far I do not think I have harmed the refrigerant lines.

There is at least some satisfaction in locating the problem. I am still doing all the work from the open front of the unit, which is hard. The other three sides are all one piece bent into a U shape to form the back and sides of the coil case. Removing it has its own set of potential problems, and my wife needs me to start to get this back together so we can again use the laundry room. At least it is a little cooler so we do not need the ac for now.

Thanks again

Good work on your end!

There is no way to repair the plastic pan since it expands so much when the furnace is on, then shrinks back a lot smaller when the cooling is on.

Your best bet will be to take the pan to a sheet metal shop and ask if they can copy it in 20 guage galvanized sheet metal.... Exactly or just an 1/8 of an inch too large.. In all dimensions, but not too small in any dimension.

Customer: replied 4 years ago.

I called the dealer from our furnace/ac and they are no longer a Maytag dealer, so they were not much help. I called and talked to a appliance parts store locally and they suggested using a high temperature (600degree) sealer. I have put that on and tested with no leaks. Next I plan to reinstall it under the coil. I will watch/test it next summer before we run the ac to see if the cracks have reopened over the winter's thermal cycling. If it is again leaking I'll go have the a sheet metal one custom made.

Thanks a lot for all of your help and ideas. I am especially thankful that you steered me away from taking apart the header. I have learned some things in the process and it has been good to have a mentor to run ideas past.

Lets hope the 600 degree F sealer holds.... I think it will be a long shot. we should all cross our fingers.