Condensation Problem.............

[Wild Comanche]

I have a 1989 4x4 Comanche.  I have got most of the bugs worked out to date,  but there is a condensation problem in cold temperatures that I haven't noticed in any other vehicle that I have owned.  I live in eastern Washington state.  So we are talking lows in the 10 to 15 degree F range.  I had the headliner replaced about 6 months ago.  It is a recovered original unit.   When the vehicle starts to warm up inside is when I notice heavy condensation forming under the headliner.  It actually runs out from under the headliner and drips on the seat.  After about 40 minutes with the heater on high the moisture will disappear.   When I had the headliner removed I noticed some rust on the inside of the roof.  I sanded it down and applied some primer to the steel.  I finally got tired of the wet conditions and put a "Dri-Z-Air" on the floor to help with the situation.  See how that works.  Just wondering if there might be a permanent fix to solve this problem.  Maybe some type of thick paint on insulation for the inside of the roof.  Or a plastic moisture barrier like is used on the doors of most vehicles.   The rebuilt headliner probably isn't as tight to the roof as the original. 

[gogmorgo]

Do you usually park somewhere warm and dry, or do you leave it outside in the cold? Snow and ice tends to work it's way into strange places that rain doesn't always get to. Could be blowing in a small leak at the top of the windshield or back window, or maybe a tiny rust hole if your rust is that bad. Cold air getting in could also be causing frost to form somewhere, especially if it's more humid in the cab from water/snow brought in on boots. 

Just a guess, but could be worth it to pull the headliner just to see where the moisture's coming from. 

[Wild Comanche]

Vehicle is parked outside in the cold.  I drove it w/o the headliner for a year or so before the repaired headliner was installed.  W/o the headliner installed in the winter the underside of the roof would be covered with water droplets, until the heater dried it out.  Condensation from differences in temperature between the outside cold and inside hot.  No, there are no leaks around the windshield.  Just had a new windshield installed 6 months ago.  The rust on the underside of the roof was very slight.  The steel is sound.  The water inside is coming from condensation.  Thanks........

[rokinn]

Is the condensation there when you get into the cab for the first time on any given day or does it develop after you start driving.  About the only time I have seen condensation develop after starting to drive is when the vehicle has an air recirculation button to prevent outside air from entering the cab, which MJ's don't have.  The temperature difference shouldn't be that great between the inside and outside unless you get a lot of solar gain, which may be the case.  I would check underneath the carpet/mat to see if there is water being held in the flooring insulation material.  If there is much water in it this would create enough humidity inside the cab to create condensation.  Mine had a lot of moisture in said insulation when I pulled out the vinyl floor covering. It wasn't easy to get to dry either.  Good time to mitigate the rust on the floor pan then as well.

[Eagle]

You are building up an unusual amount of moisture inside the cab under conditions when it should be bone dry. Winter air doesn't hold moisture. When that started happening in my '88 Cherokee, I finally realized that the heater core was leaking.

[gogmorgo]

I suppose it could also be a clogged a/c drain tube. Just thinking of other things that could be trapping moisture. There's definitely a bit much somewhere. 

[A-man930]

On 1/6/2018 at 7:33 PM, gogmorgo said:

I suppose it could also be a clogged a/c drain tube. Just thinking of other things that could be trapping moisture. There's definitely a bit much somewhere. 

This.  

[Wild Comanche]

The condensation problem is only present in temps below freezing,  but worse the colder it is.  I haven't pulled the carpet up to look at the floor.  I could do that.  The water droplets come from under the headliner.   The heater core is sound.  The condensation only happens after starting up and warming the cab up.  After 30 to 40 minutes with the heater fan on high and the heat turned up to max ; then the moisture is gone.  Haven't checked the a/c drain tube.  I could check that too.  The Dri-Z-Air I put in the rig seems to help some.  I guess they are suppose to keep the humidity down to 50%.  This maybe is something I will have to live with.....................Thanks...............

[coolwind57]

I may share my thoughts on this issue if I may.  I once had a metal building that had no roof insulation.  We operated a kiln oven, and in the wintertime, that non-insulated metal roof literally rained on us.  Frost developing overnight would become heated once we fired up the oven.  The resulting thawing caused raining inside the building.  It was an odd site, man.  

 

The solution was in insulating the roof.  I replaced the roof (it was getting pretty rough anyways) and used that vinyl bat type insulation for metal roofs.   Condensation is not allowed to form once insulated. 

 

If I had your issue, I'd likely run to Lowes or Home Depot and buy a roll of that self-sticking duct insulation stuff.  It is a thin, like 1/4" foam with adhesive on one side and aluminum backing on the other.  Its form fitting and I'd apply it then reinstall my headliner.  It would probably give you a good, noticeable difference in the Summer too from the direct hot sun.  

[rokinn]

At one point in my life my wife and I owned a VW camper van.  We occasionally slept in it in sub zero temperatures.  On these occasions, between our bodies and our moisture laden breath we would awake to frost covering the entirety of the van.  Once heat began to be produced by the heater the frost would turn to condensate and drip.  This phenomena only happened when we were in there producing humidity.  A kiln removes moisture from a substance and puts it out into the air (not to mention any other sources for ambient moisture).  The cold condensation surface is eliminated by the insulation but the humidity is still present in the air. 

 

You have a source of moisture and higher humidity in the cab that condenses onto the cold surfaces of the cab and drips when there is enough build up.  Eliminate the humidity source (whatever that may be) and you solve your problem.  If it's not obvious then it's hidden somewhere.  Like I said, the insulation under the mat/carpet can be a large reservoir of water from whatever source.  Mine happened to be poorly sealing doors which would drip water down onto the floor as snow melted or it rained.

 

Winter in eastern WA isn't the best time to be pulling up carpet but if that is indeed where the water is being held then your floor boards are rusting away.  If you can leave your windows cracked open a bit (without allowing rain or snow in) then some of the humidity will escape the cab and not condense as much in the cab until you can get at the floor.  If indeed that is where it is being stored.  Of course, as always, I could be all wet...

[HOrnbrod]

^^ This. Eliminate any and all sources of moisture collection in the cab first. Then, if needed, use a quality spray-on insulation on the roof interior, like Lizard Skin or similar. Sooner or later any stick-on batting-type insulation is going to come loose with all the temp swings a vehicle roof goes though.  

[Wild Comanche]

Thanks for the additional input.  I found I don't have a floorboard problem.  Seems in good shape.  And the a/c drain tube is clear.   I have a CJ-5 that years ago I insulated the underside of the hood with some of that duct insulation to try and hold more engine heat in the engine compartment.  The engine couldn't warm up enough in cold weather after an intake manifold and exhaust header modification.   With the Offenhauser intake and aftermarket headers they were no longer connected, hence no heat transfer from exhaust to intake.  Anyway the duct insulation helped to a certain extent.  I think I used some type of adhesive on the duct insulation.  It is still on there today, and that has been about 30 years ago.  And two years ago I installed a 205 degree F thermostat and that worked out real well.  A much smoother running engine and slightly better mileage.  I had always run a 195 degree F thermostat, but the engine always seemed it wasn't warm enough.  Back to the problem at hand;  I was thinking of using some sort of insulation.  But hadn't found a particular product.  A spray insulation,  if it wasn't too thick of a layer, sounds like it might be the trick.   And it would be permanent.   And a warmer cab in the winter and cooler in the summer.  I am not familiar with Lizard Skin.  I will check it out.  That will be a summer project as I don't have a heated shop. 

[Wild Comanche]

After working on this problem for a long time, I finally found the answer to the condensation problem.  And it is very simple.  If I leave the heater slide control in the VENT position when I shut the engine down, I NEVER have any moisture building up in the interior of my 1989 Jeep Comanche.  In any temperature, winter or summer.  I feel like a sap for not figuring this out sooner. 

[Minuit]

2 hours ago, Wild Comanche said:

After working on this problem for a long time, I finally found the answer to the condensation problem.  And it is very simple.  If I leave the heater slide control in the VENT position when I shut the engine down, I NEVER have any moisture building up in the interior of my 1989 Jeep Comanche.  In any temperature, winter or summer.  I feel like a sap for not figuring this out sooner. 

The "vent" position opens the fresh air door in the heater box, allowing the outside air to mix with the inside air once the truck is shut down. Any position except MAX A/C or OFF (which also closes the fresh air door) should have the same effect.