Air Conditioning "hum" And "ice" On Part- Rx400H

[cduluk]

Hey everyone, i think there's something wrong with my Rx400h but wanted to see what you all thought.

The temperatures are starting to get warm here in RI and for a few weeks or so i've been using the A/C. However today (~65 degrees F and rainy) i noticed a strange "humming" sound coming from the engine compartment above 5MPH only when i have the "A/C" button set to ON. Once i go below 5mph it turns off, and it also turns off when the A/C is off. But once i go above 5MPH with the A/C ON, the hum returns. I also noticed that the gas pedal was "vibrating" while the car was humming. And since the hum disappears when the car is stopped, i can't find out where it's coming from... just somewhere in the engine compartment. I have never in the past 3 years of ownership heard or FELT this humming before. And it's not the engine cooling fans as they are operating normally and it's not the new hum i'm hearing.

This happened consistently for a 30min trip, half highway and half city. When i got home, i noticed another noise which is "familiar" to the Rx400h ( which i usually hear only once and a while when the A/C is ON)- it sounds like a mini chainsaw, or "buzz" sound. It now happens whenever the A/C is ON, whether i'm moving or not. In the past i've heard this noise every once a while, but it's never stayed on for such long periods of time.

The gauge cluster engine temp gauge read normal, also.

When i inspected under the hood, i noticed my engine coolant was a bit low, so i topped it off. It only took 2 glass-fulls to top it off, so i don't think i was "that" low.

I then noticed a strange pipe with ICE on it. A LOT of ice. Once the car was turned off, in about 10 mins the ice started to melt. I've never noticed this thing covered with ice before, so i don't know if it's normal or not. The outside temp is about 65 F and i had the interior temp set to 73 with LOW fan speed... Honestly i didn't think the A/C should be stressing much!

Here are some pics of the iced part:

What do you guys think is going on? What could this humming sound be? And why the ice? Thanks for any input!

[RX400h]

While I seldom look at the engine, right after parking the RX, this home-based AC advice may apply to your situation.

You may be running low on refrigerant. Low refrigerant levels can make the cold coil too cold. Fix the refrigerant leak and fill it up.

My guess is that it is an indication that something is not right.

[drewcam888]

This ice buildup is probably because there isnt enough heat to melt the cold line of the compressor. It is normal just think in a couple months the heat will melt the ice and cause the drips under cars you see when the ac is running.

[cduluk]

God i'm lazy... For the past week and a half i've just driven without the A/C on. I need to make an appt at the dealer and i've been so busy lately. I will say though, that my mileage has been incredible without A/C (i usually average 23mpg in the summer but now i'm averaging 29mpg). i'll update whenever i get it to the dealer... Damn, i need an inspection sticker (it expired in April) and i've gotta take my license plate frames apart to put my new registration stickers on... I better not get pulled over.