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Billy
Billy, Trainer/Master tech.
Category: Nissan
Satisfied Customers: 3498
Experience:  Trainer 8+ years - master tech. 10+ years, SAE member
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I have a 2008 Nissan Altima with a Mystery AC problem. The

Customer Question

I have a 2008 Nissan Altima with a Mystery AC problem. The AC only works intermittently. History: 1. My clutch stopped engaging about 2 weeks ago and the AC of coarse would not blow cold air. 2. I immediatley shutoff the car and upon restarting the car,
the clutch engaged and the AC blew cold air just like normal. 3. The AC worked perfectly for 1 week with no repeat of the original problem. 4. The same problem then occurred 1 week ago and the clutch would not come for 2 days straight. 5. I decided to bring
the car to a recommended mechanic. 1. The mechanic noted there was not proper voltage going to the clutch. His solution - change the IPDM so it could send the proper voltage Outcome - This did not fix the problem 2. The mechanic noted that the problem now
must be a seized clutch His solution - drop in a new compressor and drier Outcome - The vacuum / leak test failed upon recovering the freon. The mechanic said there might be a leak but to drive the car home anyways and report back tomorrow if there were any
problems. The clutch engaged and the AC blew ice cold air for 15 minutes on my way home from the mechanics and the temperature gradually increased over the coarse of the day. By the next morning the Clutch was not engaging and of coarse only hot air was blowing
out of the vents. 3. The mechanic noted that the freon levels were low (after just refilling them the previous day) and presumed there must be a leak somewhere. He checked with his sniffer device and got many beeps but was unable to pinpoint where the leak
was. He once again recovered the freon and once again the vacuum / leak test failed. His solution - change the o rings on the low pressure hose. Outcome - I drove home with ice cold A/C and it lasted with no problems the entire next day. 4. 2 Days Later upon
starting my car first thing in the morning the clutch would not engage again. After driving for about 10 minutes the Clutch suddenly engaged and I had ice cold A/C for about 40 minutes. After 40 minutes the Compressor went off again and the clutch would not
engage for the remaining*****in the car. I tried numerous times to shut off the car engine and restart the car in hopes of engaging the clutch. Even waiting 10 minutes before restarting the engine would not get the clutch to engage. I drove home and
shutoff the car. 3 hours later I started the car and the clutch immediately engaged and I had Ice cold A/C again. 5. I am at my wits end and after spending $1300.00 with no solution to my problem, I am running out of confidence in the mechanics ever finding
the problem. What do you think it could be?
Submitted: 1 year ago.
Category: Nissan
Expert:  Billy replied 1 year ago.
Hello and welcome! I'm Billy and i will assist you with this.
Kindly confirm the following:
- now you don't have a leaking problem, as whenever the A/C is on, you get cold air, so we have no freon leaks.
- do you have the manual A/C with knobs, or the automatic A/C system, with digital display?
- which engine do you have (2.5, 3.5, hybrid)?
Customer: replied 1 year ago.
My car is a 2008 nissian altima 2.5
My a/c display - I included a photo I found online. I believe this is manual.
Expert:  Billy replied 1 year ago.
Hello again,
This is the automatic A/C system.
In this case, i would proceed as following:
Have a Nissan scan tool connected to the vehicle, and check the A/C module for faults. If you have no faults, try turning the A/C on, if it blows cold air, and the compressor engages, you need to wait. When the compressor disengages and you get hot air, you need to check (on the scan tool), the signals from the A/C sensors:
pressure sensor, evaporator temp sensor, ambient temp sensor, inside the vehicle temp sensor, solar or light sensor.
As any of these, if giving the wrong signal, would cause the compressor to disengage. Having checked these, you should get to the faulty one, and then check its wiring, and replace as necessary.
The most common cause would be the pressure sensor, however, we need to confirm the cause before replacing.
Kindly get back to me with your results, or if further assistance is needed, so we proceed accordingly.
Regards,
Billy
Customer: replied 1 year ago.
Where do I go for that? For some reason my mechanic was unable to connect to my car for a/c diagnostics wth the nissan software. He mumbled something about it being incompatible of which made no sense to me. Where would you suggest I go? Is this something I could purchase and do myself?
Expert:  Billy replied 1 year ago.
Hello,
The diagnostics being incompatible means that the mechanic has a generic scan tool, which would not access all systems.
You need to get to a mechanic having a specialized nissan tool (the best being the CONSULT scan tool). Any Nissan specialist and of course dealers should have such tools, to diagnose and confirm the fault.
You could buy a Nissan tool, but you would also need to know all the sensor signals to spot the faulty one. Which is no easy feat.
In short, i would get to any Nissan specialist, that can access the A/C system input and output data, to diagnose, and when the compressor is not engaging, confirm the wrong signal, and change the part (or wiring) as necessary.
Thank you for your trust! Get back to me if you need more assistance...Thank you in advance for the positive rating...
http://www.justanswer.com/car/expert-billy/
Regards,
Billy
Customer: replied 1 year ago.
Could a slow freeon leak cause an intermittent on/off clutch? I ask this because when I went back to the mechanic after he switched out the o rings on the low pressure hose (as noted in my first question), the freeon level was in acceptable range but slightly lower on both ends. He mentioned it could be slowly leaking from the radiator as the sniffer seemed to detect something in that area but he was unable to see any leakage.
Expert:  Billy replied 1 year ago.
Hello,
A slow freon leak would cause the system to get less efficient over time. IT would be ice cold at first, and the temperatures would increase with time, until the freon is very low, and then the compressor would disengage. In short, no, this is not a freon leak issue (even if you still have a leak).
Thank you for your trust! Get back to me if you need more assistance...Thank you in advance for the positive rating...
http://www.justanswer.com/car/expert-billy/
Regards,
Billy
Customer: replied 1 year ago.
One more thing I forgot to mention. The 1st day I went to the mechanic with the a/c issue he changed my car battery as my old one was in bad shape. He put the ipdm and compressor in the following day. I've read that sometimes a new battery can screw up the computer codes if not done properly. I've also read to remedy this you could disconnect the negative then positive and wait for 30 mins then reconnect positive then negative and smetimes it can reset computer issues.
Expert:  Billy replied 1 year ago.
Hello,
Replacing the battery sometime would cause the fault memory to reset. However, the faults will come back, as the faults are still present. No need, in your case, to remove the battery cables for any reset.
Regards,
Billy
Customer: replied 1 year ago.
when you say pressure sensor are you referring to the low pressure sensor? I spoke with the mechanic and he said he initially ran all these tests manually and all the sensors worked properly. Anyways, I called around town and every mechanic is booked up. I'm in Florida and its 100 degrees. I want to attempt to do some work on the car myself.
Customer: replied 1 year ago.
Please read the following: http://www.nissanclub.com/forums/2002-2006-nissan-altima-discussion-2-5-3-5/327904-c-problems-pressure-switch.htmlWhat aout replacing the switch? Could low antifreeze or needng an antifreeze flush be causing the ac to shutoff?
Expert:  Billy replied 1 year ago.
Hello again,
The refrigerant pressure sensor is located on the high pressure side of the system. It detects whether the pressure is within range. It is located on the liquid tank (on top of it) next to the condenser.
If the pressure is too low or too high, it would send the information to the A/C module, and the latter would cut the signal from the compressor. It is not an on/off switch, it sends voltage feedback from 0 to 5 volts, to indicate the high pressure in the system (high pressure in the system when the compressor is on and freon charged, should be between 200 to 225 psi). The sensor cuts if lower than 25 psi, and if higher than 400 psi.
Testing these sensors (and they should be tested simultaneously) while the compressor is not working, is impossible manually. You can check the connector on these, and even the evaporator temperature sensor cannot be reached easily, it is inside the dashboard.
If you want to try and check yourself, try first the pressure sensor, as it is easily accessible: get a multimeter, and back probe the pin in the middle (as there are three pins on this connector), the other lead of the multimeter should be at ground. You need to have the system operating, when the compressor shuts off, check if the voltage on the multimeter is below one volt or higher than 4 volts. If yes, then the pressure sensor is causing the compressor off.
PS: antifreeze or coolant have nothing to do with the A/C system.
PS: you can replace the sensor, but i would check it first, as this would reguire retrieving the freon, and refilling the system.
Kindly get back to me with your findings, or if further assistance is needed.
Regards,
Billy

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