How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Ron Your Own Question
Ron
Ron, ASE Certified Technician
Category: Toyota
Satisfied Customers: 35624
Experience:  ASE Certified Tech
7276279
Type Your Toyota Question Here...
Ron is online now
A new question is answered every 9 seconds

My a/c compressor runs continuously and doesn't continuously

Customer Question

My a/c compressor runs continuously and doesn't continuously cool passenger compartment. It cools at first but after about 10 minutes goes to temp of "vent" setting
Submitted: 2 years ago.
Category: Toyota
Expert:  Ron replied 2 years ago.
Hello, my name is ***** ***** I am a professional here at Just Answer. I have noticed that your question was not getting a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.
In order to try and determine the cause of the problem you are having the first thing you are going to need to do is to install a set of AC gauges and read the pressure with the AC compressor running, normal pressure on a full system needs to be right at 35 to 40 PSI on the low side and right at 200 to 225 PSI on the high side. Check this for me and post back with the results and we can work from there.
Customer: replied 2 years ago.
I think I have found the problem. My condenser fan has failed. I applied 12 volts directly from the battery and the fan did not operate. In addition to that, therr is a ground issue at the relay labeled "fan no.3". I attached a test light to a known ground (strut mounting bolt) and inserted the test light into terminal 85. I was able to locate power this way. The light came on with key on and went off when key was turned off. No power to the "fan no.2 relay at all. Not even using an alternate ground. The CDS fuse (30A) was blown AND melted to the tower in which it connects to. I will put my gauges on it again and retest the pressures. They were ok last time I checked. Thank you for your time. I hope you can help me solve this problem.
Expert:  Ron replied 2 years ago.

Start first with fixing the melted fuse and make sure the connection is tight or it will melt on you again. Check your pressure as well and post back and we can work from there.

Customer: replied 2 years ago.
I tested the pressures and it's 45-50 psi on the low side and about 320 psi on the high side. It's blowing cool but nowhere near as cold as it should be. Btw, replaced fuse box, condenser fan, and CDS fuse. Fan works fine now.
Expert:  Ron replied 2 years ago.

From looking at you reading your pressure are to high, inmost cases this usually means the system is either overcharged or the compressor is failing. I would start first with evacuating the system and recovering the Freon and then recharge it with the correct amount (30 ounces) . Normal pressures need to be right at 35 to 40 PSI on the low side and right at 200 to 225 PSI on the high side.

Customer: replied 2 years ago.
Wouldn't the cycling switch disable the compressor if the system was overcharged? I never added any Freon to the system since I've had the vehicle. This is something that started not long after I replaced the engine. The car has 596,000 miles on it. But if the compressor is failing, I guess it's time for it to fail. I will replace the compressor, expansion valve, and the accumulator.
Expert:  Ron replied 2 years ago.

The cycling switch works off of low pressure to shut the compressor off when the system is low. If you replace these parts , be sure to do a system flush at the same time. Please take a moment to rate my service so I can get credit for my time, the question remains open for follow up even after doing so, all you need to do is return to this question if need be.

Thank you again.

Customer: replied 2 years ago.
My a/c pressures have changed. Low side is 45 psi and high side is 240 psi. Compressor still won't cycle off. Ambient temperature is 80 degrees. Also the air coming from one side is colder than the other.
Expert:  Ron replied 2 years ago.

You pressure are reading a bit on the high side, has the system been over charged?

Customer: replied 2 years ago.
I'm not sure. I have never done any a/c work on this vehicle. I spoke with the previous owner and he said he never did a/c work to it either and he owned it 3 years and it worked fine.
Expert:  Ron replied 2 years ago.

Well I think I would start with doing a system recovery and evacuate and recharge making sure to get the proper amount and see if that solves the problem.

Customer: replied 2 years ago.
I've heard others say that but shops charge so much for that procedure. It's like $70. If that doesn't fix it, that's money wasted.
Expert:  Ron replied 2 years ago.

Well form you pressure reading the only thing im seeing is they are on the high side and that can and does affect compressor and AC performance. Under normal circumstances that the procedure any shop would take to get this diagnosed .

Customer: replied 2 years ago.
Thank you, ***** ***** know you're trying to help me. I truly appreciate it. It's just this system is all over the place and just one symptom but multiple. The only way I can get the compressor to disengage is either the button inside or unplugging the pressure switch at the drier. Now the low side pressure greatly fluctuates between 30 psi and 38 psi.
Expert:  Ron replied 2 years ago.

Its possible you may have a bad low pressure cycling switch . It may be worth a shot at replacing it.

Customer: replied 2 years ago.
Part of the problem was I did not have it set on max a/c. Mistake on my part. It started blowing ice cold but then after about 10-15 minutes it started blowing hot. I left my gauges attached and saw the low side actually went into a vacuum and high side was at 200 psi. I'm thinking a restriction in line somewhere? I will check into replacing the cycling switch.
Expert:  Ron replied 2 years ago.

If the low side is going into a vacuum then yes that indicates you have a restriction and in most cases that would be a failing expansion valve. If you end up replacing it, I would flush the system as well.

Customer: replied 2 years ago.
Would you advise changing the drier at the same time? Could I use the "sub-zero" refrigerant or should I just recharge with standard R-134a?
Expert:  Ron replied 2 years ago.

It would not hurt to change the dryer but I would stay away from the Sub Zero refrigerant, it has a very bad track record. Stay with R 134 for the best results.

Customer: replied 2 years ago.
It's nice to pinpoint the problem. It has been very evasive. I do not want to just "throw" parts at a vehicle and hope it fixes it. I want to find evidence to lead me to the problem. Given the evidence found, I believe the compressor is ok.
Expert:  Ron replied 2 years ago.

I would have to agree as long as it has the proper charge.

Customer: replied 2 years ago.
In your professional opinion, could I get by with just replacing the expansion valve, evacuation, and recharge? I'm kinda on a budget here. I want to do the repair correctly, but not spend money on something I don't absolutely have to replace.
Expert:  Ron replied 2 years ago.

You may but if the valve is bad and has debris in it then a flush would be the correct thing to do. If there is nothing in the old valve you may be okay

Customer: replied 2 years ago.
I'm in the process of gaining access to the evaporator core. Can't seem to get blower and housing out of the way. Any advice on removal?
Customer: replied 2 years ago.
I got the valve removed and it doesn't have any debris in it. The oil was clean and had a yellowish color. The outside of the evaporator core was very very dirty. I capped the open lines and used compressed air to clean it. The valve doesn't look faulty but maybe I'm wrong.
Expert:  Ron replied 2 years ago.

It a 50/50 chance its okay, If it where me, I would replace it just so I did not have to do it over again, its your call.