A/C Performance during Highway Cruise

When I first start the truck my A/C is super ice cold. I've been very impressed with it since I bought the truck. It feels great in the 110 degree Memphis heat we've been having. However, I've been traveling some longer distances recently and I've noticed that after about 45 minutes of driving (with the A/C set to Max Cool and the A/C button illuminated with re-circulation on) the A/C warms up. Now the air coming out isn't warm and is cooler than the ambient air, but it's nowhere near what the air conditioner is able to do. Once it gets stuck in this "mode" even turning the fan speed up doesn't keep the cabin as cool as I'd like, and the only way I can get it to switch back to being very cold is to turn the A/C off for a while. Any ideas?

I'm taking the truck into the dealership on Monday to squeeze the last bit I can out of the 36,000 mile warranty. Any chance they'll fix it/be able to fix it?

 

Try turning off recirculate after 10 minutes or so. Your evaporator may be freezing up and blocking air flow. You also get less musty smells from A/C when using fresh.

 

Sounds like your evap coil freezing

Not sure about in your state but here checking AC systems can get expensive.

If the pressure is low they need to check for leaks can`t just top off the system and call it good

 

Evap freeze up is high suspect. There is a sensor that lays on the face of the evap that is failing/has failed.

Since it's under warranty I'd be very specific about pointing out the behavior of the problem, and even giving them a hint about the possible solution.

If they say 'we checked it, all is good', have them document your complaint, because it won't be fixed. The documentation should let you return after the warranty ends to have it fixed on their dime.

 

Thanks guys, I'll definitely let the dealer know every detail about the problem and have my complaint documented. The evap freezing up sounds very plausible now that you mention it as sometimes I'll notice "snow" coming out of the vents when the A/C is working very well and if I turn the car off after it "freezes up" I'll notice a little condensation dripping inside the car on the passenger side. Hopefully I can get it fixed without too much trouble.

 

Bingo. That's what we needed to hear. And I bet the rest of the sentence would be 'right before the air flow drops and warms'.

Hope for an astute service writer/tech, one who is well seasoned with AC, so they 'get it' when you describe it.

Let us know the resolution, for the good of the order and all that.

 

I messed with it some more during a long trip today. You're spot on about the air flow and temperature. I was able to keep the cabin cool by turning off the compressor and letting the ice thaw whenever I noticed the airflow drop.

 

Once things get cooled off, try going off of recirc. That will bring in warmer air. If it still freezes up you could be (a) low on freon or (b) the Tx valve sensing bulb has a leak and is letting the evap core get too cold.

 

It still freezes up with re circulation off. If anything I think it freezes up faster because it's so humid here.

 

Is your compressor running full time?

 

Had it set to Max A/C. How do I tell if the compressor runs full time?

 

Visually with the hood up or just listen for it cycling on and off.

 

The sensor that has failed cycles the compressor when the evap gets to roughly 36, to prevent the freezing. Other inputs create cycling as well, but running on coldest recirculation it would normally run continuously except for that sensor.

 

I just attempted to test this in my driveway. I can't get the A/C to freeze up just sitting there, even if I hold the engine at highway speed (2500 RPM) continuously. With the truck stationary, the A/C seems to work as intended: very cold, no ice, air flow good. I didn't notice the compressor ever turn off sitting in the driveway but I also ran it for a while and didn't see any signs of freezing (frost/snow coming out of vents, reduced air flow). I suppose I'll tell this to Toyota tomorrow and have them check both the refrigerant level and that sensor.

Edit: My best guess is that the increased airflow while driving allows the A/C to exchange more heat. Considering the A/C works fine as said in my driveway, this would presumably point to the sensor being broken, not low refrigerant?

 

Edit: I agree with your edit above.

The test doesn't work because there is only fan created air flow. You need the road air flow for max system efficiency.

Don't confuse the issue by telling them what you have and haven't done, or read here. Just describe the exact behavior, on the road. They'll check (or should check) gas pressures, cycling functions etc. anyway.

But they'll need your details to dig to test/replace the sensor.

 

Update:

Took it to the dealer today. They said that the previous owner had put way too much refrigerant in the system and they found no lubrication oil for the compressor. They told me doing this is their first step and since they can't go test the vehicle for long periods on the highway, for me to come back if the problem still occurred. They added dye to the refrigerant so that if there is a leak, they can find it next time. Just from my drive home from the dealer the A/C seemed to be performing better (no ice or frost but still very cold ) though I didn't get above 50mph on my drive home. I'll post an update when I find out if it's still freezing up on the highway and again in a few weeks if I see that there is no leak.

 

I hope it works out for you, but it sounds odd to me.

Why would a 13 have had AC work done?
Why would a vehicle under warranty had the AC worked on by the PO?
If the system was significantly overcharged, why didnt it shut off/cycle on high pressure?

OTOH, if the evap sensor is bad, your problem will recur when you repeat your conditions.

Keep us posted how it works out!

 

I agree, it's all very strange. Hopefully it works out. That isn't the first weird thing about this vehicle either. The original color was apparently magnetic gray as well, at some point the PO had it painted white then sold it shortly after.
The good news is that I asked Toyota to take a look at the rest of the car since it was new to me and tell me if they saw anything unusual and they said that the vehicle (aside from the A/C) seemed to be in good working condition and that I shouldn't need to worry about anything.

 

There should be a color code in the door jamb, or a vin input into the Toyota website will tell you the color the truck came.

Could it be it came white and used replacement parts were painted after an accident? One in which the AC was damaged, then improperly repaired? If the owner did the work outside of insurance, nothing would show on carfax.......

 

I've put the VIN in to the Toyota website and it lists it as magnetic gray. I can also see on any part of the car if there is a small chip, magnetic gray is under it. Areas they didn't bother to paint like the area between the bed and the cab are magnetic gray.