My air conditioner works pretty good for the first half hour or so of a trip and after that progressively gets worse. On days like Friday when I drove 300 miles in 90+ degrees, it got to the point where it didn't feel like the A/C was doing anything at all. Got to my parent's place and checked the charge and the pressure was actually a little high I thought, around 80+ psi. So it's fully charged, I know the compressor works, what else could be causing this?

On my way back today I shut off the A/C for about 20-30 minutes and put the windows down. I put the windows back up and turned the A/C on and it was working alright again. I then noticed the floor on the passenger's side was wet and hot.

I'm not real certain how the A/C on a vehicle works. I know the basics, there's a compressor, condenser, expansion value and evaporator, but I'm not sure where all those components are other than the compressor. The "black box" under the dash on the passenger's side is cold and wet which makes me assume that's the condenser.

So what do you guys think could be the problem? I've never changed the cabin filter before, could this have an impact? Where is the cabin filter even located?

 

There is no cabin filter.

You may have a blocked drain on the evaporator housing.

You need a gauge set to read both the high and low pressures. Just one doesn't provide help with diagnosing the problem.

If that was the low pressure side it does appear a bit high.

It could be the system is overcharged or you may have a compressor problem. It can also indicate that the fan isn't working right or that there is air in the system.

Can you get both pressures?

 

You mention the fan, to me it seems like there isn't a lot of air coming out the vents at the third speed, and the fourth speed doesn't even work, hasn't work since I bought the truck or shortly there after. Not sure if that could effect anything.

I was really curious as to why the floor was not just wet, but hot. Not so hot that I couldn't touch it but certainly hotter than I think it should be. The heat goes away if the A/C is turned off.

 

The fan speed issue sounds like a problem with the blower motor resistor. Its a very common problem and usually results in some burnt wiring.

I actually meant the engine fan, the one behind the radiator or the electric fan not working properly. These can cause high "low side" pressures.

I would try to find the drain for the evaporator and clean it. The floor can get hot from the exhaust. Are you feeling engine coolant? Does it smell "sweet?"

 

As your HVAC box fills with water it picks up heat from the heater core is my guess?

As 00DakDan said put the gauges on the truck to find out what’s up.

Check your drip line it may be plugged up or stuck closed pinch it it may start dripping again. Two ways to try a fix best is use a vacuum to suck the gunk out the drip line or blow it back in with air pressure but vacuuming it out is the best.

The box filling with water may be the main problem or a small part of the problem.

 

Had a issue close to this with my daughter's car. Turn out to be over charged. Works fine now.

 

Very high humidity kills your A/C in AZ we just got a very heavy rain and its very humid now and my A/C was sucking bad today.

Yes you may be over charged.

 

I noted the floor ONLY gets hot when the A/C is on though. Turn the A/C off and the floor cools down some. The floor is wet with water, it's not coolant or anything other than water. I believe both the clutch fan and electric fan are work properly since I drove 3 hours in 90+ degree heat and the temperature gauge never went passed half way, it was in the same spot it always is when running at temp.

The A/C radiator was replaced last winter when I hit a deer and the body shop re-charged the system afterward. Perhaps they just over charged it? What's the best way to take some of the charge out. I know releasing R-134A into the atmosphere is not a great thing to be doing, so what is the "proper" way of doing this? That is, if that's the problem.

 

Nothing should be getting hot. Are you feeling any warm air blowing? Maybe it's an actuator problem. You do need to fix the clogged drain though.

Don't just "vent" it.

You won't know until you put a gauge set on it. You need to check BOTH pressures, not just the one. Since we now know that they did replace the condenser, the a/c radiator, they may have overcharged the system OR they let moisture get into the system and then not properly evacuated the system.

All of these can cause problems.

 

I am no A/C expert but 80 psi at 90 degrees seems high to me. Sounds to me like there is air in the A/C system. When air gets in the system it causes ice to form on the expansion valve, Dakota's have a fixed orifice tube, it is pretty much the same thing and is located in the low side A/C line, near the radiator. You can peel back the flex loom tubing from the line and see the 2 hex fittings in the line. You unscrew the fittings and then pull the tube out of the line with needle nose pliers and/or a pick tool.

Also it could be the A/C is overcharged. If it were my truck I would see if the shop that fixed it after you hit that deer would be willing to check the A/C system. It sounds to me like they did not pull a vacuum on it long enough and air got in the A/C system that way and/or they overcharged the freon. To be sure the air is out completely you need to pull a vacuum on the system for about 40 to maybe 45 minutes. There is a sticker on the bottom of the hood or on the hood cross member that tells the correct freon charge. If the shop that fixed it before won't look at it now, then the best thing is to have it evacuated, put a good vacuum on it and then recharge to the correct amount of freon. That may solve the problem. If not, the shop should be able to include a diagnosis of the system along with the evac/recharge and tell you what is wrong.

You can locate the A/C condensate drain tube sticking out of the lower firewall on the passenger's side of the truck. It is not easy to get to the drain tube but you can stick a cut off coat hanger or a piece of stiff wire or a long plastic zip tie up in there and clean out any trash and crap that may have plugged your drain line. That may be the cause of the water on the floor. It may also be from added condensation in the system leaking out of the HVAC box if the fixed orifice tube is iced over.

If the body shop that fixed the truck after you hit the deer fixed it during winter, it was not hot enough outside for the A/C to cycle as it should and that may have caused the shop to overcharge the system. First thing to do would be have a good A/C check done, with low and high side gauges. Then you can go from there.

Good luck, let us know what happens.