Well, sorry to keep buggin' you guys. But i really dont want to waste my money.

So i went to the shop last week to diagnose the AC. First they said they would inspect the ac (everything checked out ok). Then they evacuated and recharged the system. The guy came to me at that point and said that the mechanic looked at the compressor and said it had an internal failure (swash plate?).

The A\C works a bit, i mean about 55deg air is coming out of my vents. And on cool days it works to about 42deg (which is fine with me). But the really hot days is when i need it the most and 55deg is not cutting it.

Now, how would the mechanic know what that the compressor had an internal failure? The AC inspection checked out ok!?

Two other things come to mind. I cant place when my AC went bad, but i have recently cut the red box to the positive side of the battery. All the electrical systems still seem to function properly, but I am not sure where each of the 3 cables that go to the positive battery terminal go. Is one dedicated to the AC compressor and maybe getting partial power? I dont hear any noises coming from the passenger side of the car.

Also, i just modded my internal climate controls to have blue LEDs. Is it possible that i killed the AC control unit? Everything on it seems to function though?!

Also, how do i know it is not the evaporator?

In short, do i believe the infinity dealer that looked at my car and said my compressor needs to be replaced?

 

Listen its very simple...Go to a regular macanic after running your A/C on a hot day for a while and ask him to check it...he will connect a gauge to the high side and the low side of the lines coming out of the compressor and see if the compressor is pumping the right pressure for the high side and the right pressure for the low side...also feel the upermost line going into the firewall...it should be ice cold..
In my case on a hot day it just doesnt get cold..and it wouldnt even drip water like they all do on humid days...he took my car in for 10 min and checked the high and low sides of the compressor...mine is shot...the internals of a compressor are like an engine with a driveshaft and pistons..my driveshaft broke which is not uncommon...on wed I have a compressor from a junk yard being shipped to me for $125 (has to be the same production year as your maxima) A/C Dryer from Nissan $90 installation/flush out old aluminum parts from the old compressor that got in the lines/charge $125

I got it charged last year and it was never good enough
-Matt

 

my pressures are fine, at least i assume that is what the AC diagnostic reported.

what is the A\C dryer?

 

come on guys, i know someone here understands this

if the pressure and refrigerant levels check out, there are no leaks and the air is semi cold, what could be going on? clog? leak in the compressor, bad expansion valve?

apparently the electronics and control unit work fine. the compressor is not cycling. if there is a clog, how can that come out?

thanks

 

Reasons for not so cold A/C

1) Bad Expansion Valve
2) Improper refrigerant charge
3) Weak Compressor
4) Faulty pressure switches - Causes your compressor to cycle incorrectly.
5) Clogged Condensor fins - your car might run hot because of this also. Not enough air can pass through to your cars radiator.
6) Dirty Evaporator - http://www.keep-it-kool.com/
7) HVAC System Air passages not correct - A/C air may be still flowing through your heater core. There are flapper doors which control the air flow through your HVAC system. They direct air twards your defroster, feet and A/C outlets. They also direct air through your heater core. If the doors are not in the correct position, some of your cold air from your evaporator may be flowing back through your heater core.

And the number one reason your A/C isn't cooling off your car good enough..........

BECAUSE IT'S JUST TOO DAMN HOT OUTSIDE!

 

ok...

1. expansion valve ***

2. improper refrigent charge -- not an issue with me, i have full charge, levels and pressures.

3. weak compressor -- if the pressures are checking out ok, how could this be the case?

4. faulty pressure switch -- i am not hearing any cycling, so i dont think this is an issue.

5. clogged condensor fins ***

6. dirty evaporator *** and that website is nice, but what does it have to do with the evaporator?

7. HVAC 'flapper' is there any way to check this? i know that when i make it blow at my face, feet or defrost, that it goes to the correct vent, anything else?

*** how can these be checked? are they things that a regular diagnostic will be able to interpert its functionality?

and yes it is hot, but i know my AC can work better.

i can get a used compressor for about $50 and install it myself. then get the system charged for about $80-$100, do you guys think this is a good apporach or should i try to troubleshoot the problem some more?

thanks!

 

I know that my accessory belts are worn out. My A/C sometimes quits after awhile, especially after hard acceleration, and comes back after pushing the A/C button on and off. Could worn belts be a culprit?

 

Who told you the pressures were OK? I think you may want to try another A/C specialist for another opinion.

I'm thinking your compressor is weak and your charge isn't correct. You could be over charged. If there only measuring the low side and telling you your system pressure is OK, then their not checking the system correctly.

Our A/C system hold approx 8oz of R134a. Lets say your compressor is weak and with 8oz of refrigerent your getting 25lbs of pressure on the low side. (I think around 35 is good) So you or somebody adds a few more oz. of refrigerent to the system and brings your low side up to 35lbs but doesn't check the high side!!!! Now your charge appears correct but isn't. You've added refrigerent to bring the total pressure up, but you currently have to much refrigerent in your system. This is an indication of a weak compressor or faulty expansion valve.

I'd go get another opinion from a different A/C specialist.

 

well, i first took my car to my regular mechanic. they said that they tested the pressure and everything checked out ok. they also said that they could flush the system and recharge it, but it would have no guarantees.

then, after a week, i scheduled an appointment with my local infinity dealer. they also ran an AC diagnostic and said everything checked out. i told them to evac and recharge the system and they did it all to spec. when that did not help the cooling any, they did not charge me to recharge the system, only for the ac inspection. the mechanic there is the one who said that there is an internal compressure failure with the swash plate. i still do not understand how the ac could work at all without the swash plate working, so i have reason to doubt his judgement. It still could be the compressor i guess...

here is the only corelation with my ac working or not:
when it is below say 75F it works fine, and when it is hotter than say 85F, it hardly works at all. why would outside temperature affect it so much even after long periods of highway driving?

 

and both places i went to checked the pressure on both sides. (the edit function is not working with my browser at work).

 

I'm no A/C expert, but here's my analysis.

As outside temp changes your A/C system pressures will change as well. The Swash plate may be the device in the compressor that compensates for temp/pressure changes to make the sytem pressures stable. If that part isn't working correctly, there's your problem on hot days.

 

My AC wasn't/isn't getting cold. I also have the problem where it sometimes gets somewhat cold, and other times, barely cold. I can here the compressor clicking on and off, so the electronics seem ok.

So I went get one of those DIY recharge kits on my 1997. When I went to check the low (pressure) side, it showed high, so I was thinking, that's good, I have plenty of refridgerant, but the thing still doesn't get cold. I brought it into the Nissan dealership, they checked it out, and said that it was because the compressor needed to be replaced, to the tune of like $500-$600.

I asked my friend, a mechanic for the city, if that could be true. He said that if the low side showed high pressure, then it was possible it was the compressor. Why? I guess the system is under a constant pressure, and when the compressor is on, it pressurizes ones side, while the pressure on the other side of the compressor goes down. Well, if the compressor isn't compressing (for a lack of better word), then the low side will show high because the compressor is unable to pressurize the high side (probably due to the internal seals of the compressor being worn).

I guess this is possible since my car has the automatic climate control and has nearly 150k miles on it. Which means that the AC compressor runs a lot of the time (because I leave it on Auto most of the time).

Anyway, can I get a parts list? I had bought a used compressor off of eBay, and was going to install the new compressor, then bring it in to a shop and have them evacuate then recharge the system. Is it necessary to replace any other parts? If you could just list the parts and approximate pricing, that would be great. Thanks.

-V

 

my pressures on both sides are within spec

the swash plate is a wobbling disc on the drive shaft of the compressor, it pushes the pistons in and out.

i still dont know what the prob is.

 

Don't know if I'm 100% correct, but here's my 2 cents. Our cars use a 6 cylinder "variable displacement" compressor. That means that if varies the stroke of the pistons depending on the cooling needs. The swash plate like you said is a wobling disk connected to the drive shaft (of the compressor). The swash plate is what moves to vary the stroke of the pistons. The displacement varies from .8 cubic inches to 28 cubic inches. If the swash plate is not functioning correctly then the compressor may only be functioning at some % of it's actual capicity. That's probably why it's cool on decent days, but can't keep up on really hot days.

This is just a guess, but since I'm having the same problem I've been reading the service manual to de-bug the problem.

Also thanks for the tip on the Maxima.org discount from Courtesy, it's quite a generous discount.