A/C low pressure port at 100 psi???!!

[LeiZ]

Temperature turned 83 F here in CT this week, so I turned the A/C on, for over 10 minutes I didn't feel any cold air coming from the vent. When arrived home, parked the car, cool it down, use a gauge to measure, 100 PSI!!! I'm 100% it's the low pressure port, so which could be at culprit? And what should I do? release them all and recharge?

Advice is greatly appreciated. Thanks, guys!

Sincerely,
Lei

[TiAgX5]

Needs to be running with AC on max to check.

[upallnight]

Originally Posted by LeiZ

Temperature turned 83 F here in CT this week, so I turned the A/C on, for over 10 minutes I didn't feel any cold air coming from the vent. When arrived home, parked the car, cool it down, use a gauge to measure, 100 PSI!!! I'm 100% it's the low pressure port, so which could be at culprit? And what should I do? release them all and recharge?

Advice is greatly appreciated. Thanks, guys!

Sincerely,
Lei

You wouldn't be able to connect the gauge to it if it was the high pressure port. These thing are basically idiot proof compare with R12 system, but there is always that 1 idiot that proves me wrong.


An initial low side pressure of 100 psi is not abnormal if the compressor is not running and the underhood temps are high enough. Once the compressor engages, the low side should drop and continue dropping down to around 20-25 psi. At this point, the cycling switch should open. The pressure should rise to around 45 psi, at which point the switch should close and the cycle should repeat.

Is the compressor running? If the compressor is running and you are getting that type of reading on the low side most likely you need a new compressor.

If you don't hear a click when you turn on the ac that means the clutch didn't engage. You can verify this by looking at the center of the ac compressor pulley. Is the center revolving or is it stationary. If it is stationary that is the reasons why you don't have AC.

[cn90]

You need to read this on the working principles of AC system:
Summer A/C Guide, How it Works, and When it Doesn't - Honda-Tech

Think AC pressure btw LO anh HI sides as "tide" in the ocean.

When Ac is off, pressure is the same on both LO and HI sides, approx at 90-100 psi. In fact, with engine off, checking the LO side and if it is around 90-100 psi, you likely have enough R134a.

When AC is on, R134a is pumped (by the AC compressor) from the LO to HI side, so typical LO side P is about 30-35 psi. HI side about 250-300 psi. The analogy I try to make is "tide" in the ocean, water is raised on one side and low on the other side.

The best AC is always when the car is cruising on highway. At idle (parking lot), there is minimal air flow through the front.

[David.X5]

I agree with the comment above. With nothing running, If the system is filled, there should be some liquid with vapor over that. The pressure of the vapor increases with temperature. At 85F you would expect 95 psi vapor. At 90F you would see 104 psi. Once the compressor is running, low side pressure will drop and high side will go up. This information is not enough to decide the system is full, but it has enough refrigerant to have liquid and should be able to run.

There are various reasons the compressor may not run or the system not cool even when the compressor is running.

[LeiZ]

FIXED!!!!

You guys are THE BEST!! Start the car, turn the A/C on, THEN put the gauge on, and the pressure quickly dropped to less than 15 psi. Recharge it back to 35 psi while running, and the vent is blowing freezing cold air again. Whoooray!!!!

Just wanna say thanks again! This forum rocks!

[upallnight]

Originally Posted by LeiZ

FIXED!!!!

You guys are THE BEST!! Start the car, turn the A/C on, THEN put the gauge on, and the pressure quickly dropped to less than 15 psi. Recharge it back to 35 psi while running, and the vent is blowing freezing cold air again. Whoooray!!!!

Just wanna say thanks again! This forum rocks!

This might have been a quick fix, but the problem is still there. You are leaking refrigerant into the air. I would not call it a FIXED until the leak is found and repaired.

[puddinboo]

^ 100% agree

[LVP]

When I got my X5, the AC didn't work. I took it to a shop that did a proper evac and then refilled the system with a leak sealer and dye. I think this is the proper way to do it, so if there is a leak, you can find it.

[upallnight]

Originally Posted by LVP

When I got my X5, the AC didn't work. I took it to a shop that did a proper evac and then refilled the system with a leak sealer and dye. I think this is the proper way to do it, so if there is a leak, you can find it.

Dye will only work if you can spot the leak. A leak in the evaporator coil will not be able to see because of the location.

I brought an E34 Touring because the lady that owned it before me brought it in every year to have the refrigerant top off. She inquired about having the system fix and since they couldn't find the leak they told her it would cost more than what the car was worth to fix the AC. Got the car for a song because of a non working Ac. Used a sniffer to locate the leak and replaced the condensing coil. The AC was still blowing cold when I sold it to a BMW mechanic.