[Carlo Manfredini]

Just bought an '06 Highlander Hybrid that blows warm air when the AC is maxed out. Pressure gauge reads red when attached to the low pressure valve. I'm assuming there's too much refrigerant? The compressor makes no noise when turning it on/off. I'd greatly appreciate your input!

 

[C R]

They may have tried to refill with refrigerant without evacuating the system. Running it could cause damage. Have it professionally serviced.

 

[Mgeorge]

do you have the ac running when you check the pressure?

 

[Carlo Manfredini]

Yes. The shop put two used compressors on my car, neither solved the problem. Not even a brand new one would cause the compressor to engage. I have no idea what in the world is going on.

 

[C R]

Ask your question on the Hybrid forum too. They really are two different vehicles.
Use a scanner to see if the AC clutch is being turned on by the ECM. Conditions need to be correct.

 

[C R]

Also, do you have a check engine light on or any pending codes?

 

[Carlo Manfredini]

No check engine light and no pending codes can be detected. I'll see if the Hybrid forum might be able to assist me. I'll probably take my car to the dealer tomorrow.

 

[Carlo Manfredini]

Thank you for your assistance guys.

 

[Mgeorge]

you said yes the compressor was running when you checked pressures, then said the compressors wouldn't engage... If the compressor isn't engaged you can't get a meaningful pressure reading, and don't need one until you figure out why the compressor isn't engaging.

 

[AstorsWood]

Recharge refrigerant is very easy.

Go to Autozone to rent vacuum pump and pressure gauge.
There are many YouTube video on how to do it.
What I did are:
1. pump vacuum to given psi value.
2. hold for overnight, compare psi before and after overnight. Change should be very small. IF there is large vacuum drop, fix leak first.
3. charge refrigerant.

Good luck!

 

[Carlo Manfredini]

I repeat, the compressor does not engage when the AC button is turned on. I've replaced the compressor 3 times and the compressor still won't engage.

 

[AstorsWood]

I never had this issue before, don’t count my comment as an expert advice. I am a physicist and always work on my car. Anytime, when my car had problem, I try to understand how it works.

Most AC compressor control by a coil. When car is idle, you can check if it is coil problem.
Most car electronic use 12 V DC. Apply 12 V on the coil, you should hear click sound, if not coil is bad.
If coil is OK, run engine and turn on AC, measure voltage on coil, it should be 12 V DC. Be careful what you do this, because car is running. If both works, compressor should engage when you turn on AC. Check Toyota Highlander repair manual, to make sure what I said is correct before do it.

 

[C R]

Check the fuses and relay, then see if you have voltage at the compressor clutch. If not then used a scanner that can access the AC clutch command from the ECM

 

[alltoyo]

Yes. The shop put two used compressors on my car, neither solved the problem. Not even a brand new one would cause the compressor to engage. I have no idea what in the world is going on.

your going to the wrong shop, replacing a compressor because it doesn't engage doesn't sound right

 

[alltoyo]

Recharge refrigerant is very easy.

Go to Autozone to rent vacuum pump and pressure gauge.
There are many YouTube video on how to do it.
What I did are:
1. pump vacuum to given psi value.
2. hold for overnight, compare psi before and after overnight. Change should be very small. IF there is large vacuum drop, fix leak first.
3. charge refrigerant.

Good luck!

by epa stds and laws the refrigerant must be properly recovered and not vented to the atmos, vacuum is measured in inches of mercury/mm mercury/milibars, not psi. a/c systems really should be serviced with by experienced licensed pros