Blowing out the evaporator drain tube

[rationull]

I noticed yesterday after running the AC on the way home from work that there was no puddle on my garage floor. I'm not sure if this could be just because the heat here is dry heat, but I don't want to find out by waiting for water to leak onto the floor in the car.

I always hear that you can blow out the evap drain tube with compressed air, but almost never any more detail than that. Blowing from underneath the car would be convenient, but it seems like that would just blow whatever's clogging it up into the assembly, and lead to worse clogs in the future. Is the "real" way actually to get at the drain hose from its source and blow the crud out rather than in? If so, how much of a PITA does that usually end up being?

 

[adamg]

What kind of car? Some cars (like my Civic), you can remove the rubber hose (about 4" long), and clean it, no tools required. I usually do that when I'm under changing the oil, but it hasn't had anything in it yet.

 

[ffhdriver]

you would not be smart to blow air back toward the evaporator. Carefully running a wire up the hose should work if you can't find the hose at the HVAC assembly.

 

[rationull]

The car is a 2007 Civic. I couldn't find anything in the service manual but now that you mention it, the parts diagrams online do kind of make it look like the drain hose is short and detachable. As it happens I need to change the oil tomorrow anyway, so I'll find it and take it off.

ffhdriver: noted about using a wire instead. That makes sense. It just seems strange that there seems to be so much advice out there about blowing it out with an air hose.

 

[mechtech2]

There may be nothing wrong.
Is there an unusual smell to the AC? That is often a clue.
Did you have it on recirculate or fresh air?

 

[rationull]

I'm pretty sure I had it on fresh air. No unusual smell coming from the vents that I've noticed. But I do occasionally get a "humid" smell when starting it up getting back in the car after it's been off for 15 minutes, on days when it's more humid out.

 

[rationull]

Well, I found it, but it was more hidden than I thought it would be from looking at the parts diagrams. It looks like it might actually be more accessible from inside if some of the lower passenger side trim were removed but I'm not getting into that today.

I shoved some small gauge electrical wire up there and didn't feel any restrictions that didn't just feel like a curve in the hose. So, I attached a tube to it and blew through it and didn't feel any restrictions either. For good measure I then put the tube up against the end of the hose from a relatively powerful vacuum cleaner and nothing came out.

I guess it was just the dry heat causing no puddle.

 

[Kestas]

What are the dew points around you?

Edit: You didn't say where in California you live, but a check on a random city in So. California presently shows a dew point of 50°F. This is high enough that you should see condensation from your a/c, unless you run in on recirc mode.

 

[rationull]

I'm on the CA central coast. Not sure what the weather was specifically when I posted this but right now the dew point around me is 40-43 deg F. If anything it was hotter and less humid last week.

I assume this is still high enough, but I was running with a pretty low fan speed toward the end of the drive and it probably just dried out before I got to my garage. Not too worried since the drain didn't seem clogged.

 

[Kestas]

I'd say 40-43°F is borderline. The evaporator is somewhere above 32°F, and could be above 40° if the a/c system isn't perfectly efficient. So yes, your system may not be developing any condensation, or the condensation is very minimal.

 

[KrisZ]

On my Mazda 3 The drain tube is transparent and clearly visible from the engine compartment, so inspection is easy.

I noticed, that if I shut the car off with the AC still being on, I will have a puddle, but if I turn off the AC and leave the fan on a minute or so before I arrive at my destination, there is no puddle, as all the water escapes. I heard that this prevents mild from growing, which causes the mildew smell.

I try to do this as often as possible, and so far, after 3.5 years, only on some occasion I have a slight mildew/humid smell comming from vents when I firs turn the AC on.

EDIT:

Come to think of it, I think I picked up this trick form BITOG back in 2005

, and I think it does help with getting rid of condensation on the evaporator core

 

[rationull]

Originally Posted By: KrisZ
On my Mazda 3 The drain tube is transparent and clearly visible from the engine compartment, so inspection is easy.

I noticed, that if I shut the car off with the AC still being on, I will have a puddle, but if I turn off the AC and leave the fan on a minute or so before I arrive at my destination, there is no puddle, as all the water escapes. I heard that this prevents mild from growing, which causes the mildew smell.


I have noticed this on the Mazda3 as well -- it's pretty nice.

That actually might be why I wasn't seeing a puddle. I usually turn the AC off a bit before turning the car off. Although I usually turn the fan off too since I have to go through a dirt alley to get to my garage and figure I might as well not suck extra stuff info the cabin filter if I can avoid it.