Hey guys. I am posting this for a friend. Here's the issue.

He's got a 2004 GS300 with 30,000 miles with a serious condensation problem. Apparently, both of the rear door windows and the rear window consistently fog up and the condensation won't go away. It's kind of strange because the condensation only forms on the rear door windows and the rear window, but not the windshield or the front door windows. Has anyone else experienced this problem? Regardless, does anyone have any ideas as to what could be causing it? I have several ideas of what might be the cause, but I don't want to throw them out there until I hear what everyone else has to say. By the way, he had the car checked out at Lexus and the recirculation door is working fine, so fresh air is coming into the car.

Let me know what you guys think. Thanks.

e-man

 

Okay, since no one has responded yet, and I'm getting ready to go to bed, here are some of the things I thought it could be:

a/c compressor stuck in off position
water back up in moonroof drainage tubes
blocked air cabin filter
leak in heater core (although there's no smell, so I don't think it's this)

Does anyone have any other ideas?

 

Hey E don't worrie when you wake up, I'm sure there will be plenty of ideas to fix your freinds problem now go to bed

 

Here's one to check on, clogged door drains. Occasionally water gets into the doors from car washes, rain etc., there are usually weep holes in the bottom of the doors to allow this to drain.

 

^ I'm thinking something along those lines. if not in the doors, there has to be moisture somewhere back there that is evaporating,causing the moisture to form on the windows. Is he sure carpets, rear deck, seats, trunk area all dry? sometimes water collects near spare tire too.

 

Good suggestion GW. It wouldn't explain the moisture on the rear window, but it would definitely explain the moisture on the rear door windows (although what are the chances that both rear doors are clogged up). Anyway, you never know, and it's definitely worth passing it along.

Yep -- it has to be something back there because he's not getting it in the front (although the front door windows have vents blowing air on them, as does the windshield). I was also thinking he should check for moisture in the trunk as well (maybe the moonroof drain tubes are all clogged up).

Anyway, keep the suggestions coming. This is really helpful.

 

I like the water-in-the-door theory.

What about cabin air circulation issues? Could it be air flow problems to the vents beneath the front seats and the vents in the rear of the center console?

 

That's another great suggestion. I forgot about those vents.

 

Going to the basics ...

When air containing moisture is cooled (touches cold surface) the temprature drops and air molecules bunch up closer ... squeezing out moisture (vapors) and deposits them on the surface.

Solution steps:

1. Clean the surface. [This reduces the surface area .. consider dirt as hills and valleys on the glass]. When you wash the car clean the inside surface of the glass. Rear window is a pain in GS.

2. Heat the surface. Use rear window de-froster. The front has vents. For rear paly with the vents and fan speed and direct as much hot air as possible to the glass surface(s).

3. Heat the cabin air: Once the cabin gets warm the the capacity to carry moisture will go up + surface will get warm as well. [Note for a while the condensation will be worse as there will be a differential in the cabin temp and the glass temp].

4. Reduce moisture:
Run A/C [climate control should turn it on with defrost settings] This causes the condensation to happen in the A/C heat exchanger. [Note: if cooling does not happen then there may be residue moisture in the heat exchanger which may add to the moisture problem ... specially if the drain tube is plugged etc.
Simple things like put the umbrella, wet rain-coats/jackets in the trunk.
If the air outside is drier then let it in to displace the moisture rich air we breath-out.

Most bang for the buck .. Clean the glass, run A/C, keep the wet stuff in the trunk.

Salim