Sort of a good A/C problem?

[Flopster843]

Hey fellow TDR guys. I have a "situation" that I thought you guys might be able to help with. While on a road trip this past weekend and sitting on the passenger side for a spell, I happened to notice some water drops on the passenger floor mat. I pulled out the glove box and found this:


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I have recently installed a new evaporator core from 4 seasons and a full set of aluminum HVAC doors. System was re-charged to factory spec after the upgrade. My AC is much colder than it ever was from the factory and I no longer need to use the heater core bypass valve to keep vent temps down. I am able to her a "SHHH" noise coming from the evaporator every time the compressor cycles, but you can't hear it if the radio is on. I'm not worried about the noise, but I'm not a big fan of condensation dripping inside the truck. If I keep the system on recirculate the air will dry out enough to stop the condensation but it takes 15-20 minutes. In that time, there's a quarter size wet spot on the floor. If I keep the AC on fresh air mode, the condensation will stay until I put it back on recirculate.

I'm happy that I finally got the AC working like it should have been from the factory and I don't want to decrease it's performance because of this. Any thoughts?

 

[PWong]

Apply some insulation on the air box.
Put a paper tower underneath the air box.
Avoid the fresh air mode.
Reduce the performance.
Any one or combination of the above would work.:-laf

 

[Motorhead]

The areas of Texas I have been in are very humid. By having outside air coming in (regular AC mode) you are taking outside, humid air and cooling it. That is contributing to the condensation. When you run recirc, you are re-cooling and drying out the air that is cooling you in the cabin. Is your AC moisture drain clear?

 

[Flopster843]

The entire box was removed and cleaned several weeks ago when the new evaporator was put in, so I'm positive the drain is free. It does flow pretty good when the system is on. It has been really humid this summer and I know the extra moisture isn't doing me any good. On recirculate it will dry up after a while, but it gets wet every time I get in the truck and turn the AC on. Luckily it drips on the floor mat, so I might just have to live with it during the humid season. It's just odd that it never happened before.

 

[Motorhead]

John, Have you checked what your outlet temperatures are? It may be colder output now with the new evaporator. Did you place the thermistor back in the same place on the evaporator? That is the cut out for the compressor circuit when the surface of the evaporator gets to a certain temperature. Normal outlet temps can vary but 40 to 42 degrees is normal for most.

 

[Flopster843]

The 2008s don't have a thermistor in the evaporator like the older ones, at least mine doesn't. It's mounted to the box and touches the face of the evaporator. It's the white connector in the picture above and you can see it in the second part of my HVAC rebuild video at about the 13 minute mark. I can get the vent temps down to about 35-36 degrees now. Previously I could get it down to 41 at the lowest point, but it typically ran in the mid to upper 40s. I dropped roughly 10 degrees with the new core, which is the reason for the condensation. I've watched the evaporator with it running using a camera through the recirculation door and it's not freezing, but I'm sure it's not far from it.

 

[PWong]

Just apply some foam insulation on the sweating areas.

 

[RVTRKN]

Well it could be good or bad.

BAD, it's getting so cold, it could be in the freezing temperature range. If it ices up, it can destroy the new evaporator. I'm not talking about air temperature, but the refrigerant temperature.

GOOD, it's running just above the coldest allowed, before the evaporator freezes up.

Either way, you might want to check the pressures, to confirm the refrigerant pressure/temperature relationship