Skip the auto shop - Our mechanics make house calls

Q: High pressure side of A/C is low (30 psi)

asked by on

The air compressor low side is at its normal psi. It kicks the compressor on and off between 26 and 30 psi. The high side does not move and it is at 30psi. It should be at 220psi. There are brand new expansion valves so those have been factored out as the problem. The condensor works properly. There is also brand new low pressure and high pressure switchs. Also a brand new trinary switch. All are in working order. What could possibly be making the high side such a low psi? We also charged the system anywhere between 3lbs and 6lbs. That has done nothing to the pressures at all.

A: Hi there. It sounds like the AC compressor ...

Hi there. It sounds like the AC compressor internal valve or the compressor itself has failed and is allowing refrigerant to sit freely and preventing pressure from accumulating; no suction and no discharge equals same pressure on both sides. You could also have a failed ac clutch or relay not engaging the compressor. I strongly suggest asking a qualified technician to perform an inspection to avoid replacing unnecessary parts. YourMechanic has several technicians available who can assist you with an AC does not work inspection.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Save up to 30%

Get a quote

What others are asking

Q: How do you use the air conditioner?

Without a working air conditioner, the interior of your car can get very hot. Most models come with air conditioning as a standard feature, but you’ll need to verify that yours has it (some don’t). Here’s how to turn on...

Q: Clutch not engaging with compressor

If the air conditioning clutch is not engaging, then there may perhaps be some sort of electrical problem. Sometimes a fuse can blow, or a switch can go bad, and that will disable the clutch from turning on. It is...

Q: Air conditioning is useless now and it’s summer

Greetings and thank you for writing in with this question! A/C problems can be caused by a number of failed components. Does the vehicle have rear A/C? If so, does the front work while the rear doesn’t? This would indicate...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
How to Renew Your Car Registration in Oklahoma(DELETED)
Having your car registered with the Oklahoma Tax Commission is an important part of driving legally in this state. You will need to do this within 30 days of moving to Oklahoma...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.