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A/C condensation drain question

Discussion in 'General Chevy & GM Tech Questions' started by palmer_df0130, Jul 23, 2013.

  1. palmer_df0130

    palmer_df0130 Rockstar

    I have 99 Chevy Silverado Z71 that the a/c works great in, but only drains the condensation out while the a/c is on. If I drive with the a/c for a considerable time for condensation to build, park and and shut the truck off , it may drip a little. But, if I turn the key to run without starting the truck and turn on the fan it will gush a lot of water out. A friend of mine has an '04 Silverado that gushes out water after he shuts his truck down. I tried running a stiff zip tie up the drain, but it didn't seem clogged. Any suggestions on what I should try next or is it normal? Thanks.
  2. j cat

    j cat Rockstar 4 Years 1000 Posts

    If you have a dirty evaporator or the air box filter is dirty the evap will freeze . then on shut down melt. when you start the air flow back up any water in the air box shoulde blow out.

    I would remove blower and clean out the air box/filter /evap coils .
  3. palmer_df0130

    palmer_df0130 Rockstar

    Thanks for the response j cat. I am getting ready to head outside and take a look at it.

    - - - Updated - - -

    Filters were good and filter side of evaporator is clean from top to bottom with no obstructions that I can see. Is there a way to drop the bottom housing so I can get a better look under the evaporator? I tried blowing air in through the drain outlet side but nothing changed. It will only drain a little bit of condensate out after parking and shutting the a/c off, but if I were to turn the key to on immediately after parking, engine off, and fan on, it will push it out. Maybe the drive is not long enough to build up a considerate amount of condensation to make it gush out after parking. Good thing is it is not coming into the cab or getting into the blower. I guess I will just leave it be since it is cooling great in this AZ heat.

    - - - Updated - - -

    I just noticed that there is an evaporator filter on the opposite side of where the cabin air filter goes. How would you even attempt to clean it or change it out? Also, Which way does the air flow through the system? Does it come from the blower and push the air from right to left through the cabin air filters and then across the evaporator?
  4. j cat

    j cat Rockstar 4 Years 1000 Posts

    the blower sucks air from the hood firewall grill. then the air blows toward the driverside of the vehicle past the resistors/relay control assy to the air filters [2] side by side. with the filters removed you will see the evap coils. now lets say this is all clean and still the water you feel does not drain properly well if no water comes in to the vehicle that is good because if it was bad you would have water leak into the passenger side. where you live animals like lizards will make a home in there.

    you could try to spray water at the evap coils and see if it drains out . place a container to catch the draining water to see if you have debris in there coming out.
  5. palmer_df0130

    palmer_df0130 Rockstar

    Thanks again j cat. I will try spraying some water in there and see if it flows freely.

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