Lamborghini Aventador strange pressure readings

[Ctravis595]

This is my first post in the forum, for some background I was a Mercedes Benz technician for a few years, and am certified in auto r134/1234 systems

I have since opened my own repair company, servicing primarily Mercedes, and have started branching out into more Lamborghini, Ferrari, Rolls Royce, Bentley, etc

We have a good client who says the a/c is not blowing cold on his 2016 Lamborghini Aventador. I was surprised to see that the service ports for the car require the hood to be removed from the car, and the trunk tub to be removed. I confirmed his complaint that the ac was not very cold. At best, the passenger side air vents seem to have “some” cooling effect. That was the first time I’ve removed the hood of a car for anything besides an engine swap.

We began by recording static pressures of the a/c system.

Low side reads around 65psi
High side reads around 150psi

Normally I am used to seeing similar high and low side pressures with the car off…But I figured maybe there is something to this ac system I am not familiar with, perhaps the high side stays high to reduce the amount of labor the compressor is responsible for? After all we have only done ac stuff on Lamborghinis a handful of times … I don’t want to jump to conclusions

We started the car and ran the ac to find even more strange behavior

With the car/ac running the pressures are

Low side 30psi
High side 65psi

I have never seen any car have a high static pressure on the high side, and such a significant drop in high side pressure while the car is running.

The difference in pressure shows that the compressor is doing something. The low side pressure dropping while the car is running shows me the compressor is performing some suction duty. The high side pressure dropping while the car is running is very strange to me

I wanted to see if pressures changed at all with a bit of refrigerant added to the system, strangely the addition of a bit of refrigerant seems to have no change to high or low side pressures

The high side holding 150psi while the car is off indicates to me the high side is able to hold at least some pressure. If there is a leak I believe it is a small one at best.

I am reluctant to recommend a typical “evac, vacuum, recharge with dye and find the leak” which typically leads us to solve 90% of the ac problems regarding low ac pressures we see here in Florida, whether that leads to finding a leaking condenser, compressor, bad seal. etc

If anyone has any advice as to these strange readings I am interested in learning more. This just not something I’ve seen before and searching for related stories with these symptoms is hard to find

[tbirdtbird]

We need both hi and low pressures at 1500-1800 rpm. Idle numbers carry very little weight. At the same time record the ambient at the grill (not weather channel). Also record center vent temp with electronic thermometer. Have the windows open and AC set to max cooling and max fan. You want a good load test

[Ctravis595]

The client has the vehicle now

Just curious what can cause 150psi on high side while car is off, and somehow drops to 50psi while the car is running

[bohica2xo]

Recover the system. Probably low on charge. Remove the expansion device, and see if the tractor factory left any junk in the system when they assembled it.

Those cars are rarely high mileage vehicles. Leaks over time while sitting are more common. Unless you bought the car from Ed Bolian...

[Tim]

Electric direct drive compressor. 100% make sure the charge level is perfect. I can't tell if that's a speed sensor, probably, or a control valve at the switch plug base.

14-0401NIP

[tbirdtbird]

Glad to see you back, Bohica!

[Ctravis595]

Recover the system. Probably low on charge. Remove the expansion device, and see if the tractor factory left any junk in the system when they assembled it.

Those cars are rarely high mileage vehicles. Leaks over time while sitting are more common. Unless you bought the car from Ed Bolian...

Wow you were dead-on it seems

Today we got to spend some more quality time with this car

Evac/vacuumed and recharged. Still has funky pressure readings, a/c still blows warm

While checking out a/c lines I think I found the problem, there is a 60f degree temperature difference between inlet and outlet of the drier. One side of the drier is warm and the other side is sweating condensation. 101f on the blockage side, 40f on the other side

Thanks for the suggestion for the blockage. This was the first car I have diagnosed using an infrared temp gun along the ac lines until I found a significant difference in temperature, to me this indicates a clog

Client was informed ac system may need more than just a drier, wouldn’t be surprised if this car requires engine to be removed to replace the compressor…