A/C dripping from condensation?
 

This is my first "hotrod" with A/C and I just got back from my first road trip, (about 4 hours each way). It was mid to high 80's and pretty humid.
The A/C worked great, except after an hour or so on the road it started to drip condensate from the outside of the floor vent and A/C housing onto the passenger floor and later dripped from under the dash onto my feet. The dripping was substantial. My wife had to cover her feet with a towel to keep them & the carpet dry. I was also worried about my stereo unit getting ruined, and this maybe even causing an electrical short.
The dripping doesn't occur when driving the 10 to 40 miles I normally drive the car. But I will almost always see vapor condense on the center dash vent.

On a scale of 1-10, this is a "3" of concern to me.

I called V-A & they said it is simply a function of the air temp differential, and is "normal". I have never experienced this in any other A/C'd car, although they weren't black cars with aftermarket air.

The normal condensation drain is not leaking inside the car and is working fine as best I can tell.

Have you experienced this? Ever heard of it?
Do you worry enough about it to fix it? Maybe insulate the ducts?

Any experience shared is appreciated.

Bill

I've got something similar happening with a vehicle in the shop right now with a Vintage Air System. Driving on surface streets with stop and go traffic there is no issue, but extended highway driving (45min+) it starts getting condensation dripping out of the evap case inside the vehicle. I've already verified the evaporator case drain is clear and I get normal condensation drip with normal driving. My guess at this point is that the evaporator is icing up and blocking the evaporator case drain. The car is apart right now for other work so I haven't been able to test my theory yet by playing with the blend and adding some heat into the case to see if it keep sit defrosted.

Try adding a little heat on your blend to see if it helps. These systems run a heater bypass valve to keep hot coolant out of the evaporator case when on full cold so the A/C blows colder...but it could be getting too cold.

If I remember my A/C theory propoperly an overcharged system could also cause an evaporator to ice up. Most of my experience before the pro-touring work was with fixed orifice tube systems rather than expansion valves as all of these aftermarket systems seem to be.

Sean,
Mine was definitely freezing up last summer, as it would slowly drip from the drain for hours after I shut it off after driving with the A/C. But I opened the system last winter, and had it charged with the correct amount of 134 (1.4# if I remember) by a shop this spring. It shouldn't be freezing up, but who knows? I was thinking about it freezing, but didn't know how that would lead to the dripping. If anything, it should start blowing warmer as you lose airflow over the evaporator from the ice formation.
Funny you mention adding heat. I wondered about that too, so I questioned V/A about it. They said not to do so. It would not help, and would simply hinder the performance of the system.
It makes me a little less concerned than thinking mine is the only one doing this, but I am still not comfortable with water dripping on electrical stuff & stereo equipment.

Anyone else ever fixed this?

Bill

The evaporator is likely not icing up, as that would restrict the airflow through the evaporator and cause warm air to blow out of the vents.

A couple things come to mind:

Ensure the drain is clear, and that it is at the lowest portion of the evaporator case.

If water is condensing on the outside of the ducts, try wrapping them with insulation.

Metal outlets will usually have condensation and dripping (this was common on cars "back in the day"). There isn't much that can be done about this.

One thing that can help is, once the temperature in the car is where you want it, leave the fan on a medium setting and increase the temperature setting.

Insulating the under dash area (including hush panels under the dash) can help reduce condensation.

VTA gives you a little strip of tar like paper. I had to cover all the metal sections of the interior tubing. Mainly the high side. I've used Dynamat and home depot stick on foam insulation too.

Never had it come from the vents though.

Did you seal all the vents and holes in the firewall? It sounds to me like you have a lot of outside air leaking into the car.

Don

Thanks for the suggestions. I will look for air leaking (maybe the kick panel vents are open) and try some duct insulation if there is room. But it is very tight under the dash.

I don't have any more long trips scheduled for this summer, so it shouldn't be a big issue for a while.

Bill

Aren't the kick panel and dash vents supposed to be sealed off? At least that is my recollection.

Don

Speaking of air/cabin leaks: What about A/C in a convertible, air on with the top down. Is that going to create a condensate problem ?

Tim john---

It shouldn't matter. Condensation is suppose to drain out like it should.

For OP, call Vintage Air, and get their answer.