Refrigerant Type: R134a
1993 Maxima, factory R134 system. I've spent the past year overhauling this car and just got it back on the road last week. So this is my first time driving it in about a year. Never had an a/c performance issue with it previously, but keep in mind it has been sitting for a year.
Driving it around these past few days I've noticed it will blow completely warm air for long stretches. When I say long stretches, it's probably 3-5 minutes - long enough to get me hot and borderline sweating in the car. The frustrating thing is, it will then blow ice cold air for a minute or so, in between the longer stretches of warm air. When the air is blowing cold it feels as cold as I am accustomed to with it.
Now, with this car being much more substantial than my Civic, I can't *feel* when the compressor cycles on and off like I can in my Civic. In the Civic, when the compressor engages it feels like I suddenly have an extra passenger lol. In the Maxima, I'm oblivious to whether or not the compressor is engaged. Having said that, I'm *assuming* when the car is blowing warm air that the compressor has cycled off, and when it blows cold air for the short stretches that it has cycled back on.
Given the fact that it blows very cold air during those times that it does work (the times I'm assuming the compressor is engaging) leads me to believe there is not an issue with the amount of refrigerant (ie, it's not just simply low).
So this leads me to believe its an electrical issue?
Would appreciate any input on my assumptions and help as to how to go about fixing it. Thanks
No the system has never been opened.
I have a manifold gauge set but frankly I don't know the logistics of using them for diagnostic purposes. More specifically, I have read a lot about a/c stuff over the past few years and they discuss reading the gauges and what different pressures mean but I've never clearly understood WHEN to hook them up and WHEN to read them. I realize this is so elementary most guides seem to skip this stuff as they assume the reader knows, but to somebody like me who had/has no experience using the gauges for diagnostics I fundamentally am ignorant of WHEN to hook them up:
Do I start the car, turn on the A/C, hook the gauges up, then get the readings?
Do I hook up the gauges with the car off and read it that way?
Do I hook the gauges up with the car off, then start the car and the A/C and then read the gauges at some point after that?
While it is blowing warm, pull over leaving the engine running and the A/C button pressed. Open the hood and see if the compressor is engaged.
Failure to engage consistently is typically from clutch gap too wide or the compressor relay is bad.
I'm inclined to think you don't have a refrigeration problem. I wouldn't hook up gauges just yet. Will it blow warm for 3-5 minutes then cold for 1 minute when you're sitting in the driveway? If so, look and see if the compressor is on or not. Also, what are the radiator fans doing? They should be on if the A/C is on and the weather isn't too cool.
Did the A/C work properly before you started overhauling the car ?
Also , check for vacuum and / or electrical sensors / devices / gadgets that may be inadvertantly disconnected .
Edited: Thu May 23, 2013 at 5:09 PM by WyrTwister
Thanks for all the input guys. WyrTwister, thanks, that's exactly the type of explanation I've been needing regarding my gauges.
When I got home from work tonight the air was blowing warm so I kept the car running in the driveway and popped the hood to see if the compressor was engaging. It wasn't, so I sat and watched it for a few minutes. It never engaged so I went into the cabin and turned the a/c switch off, then back on. The compressor immediately engaged so then I went back to the engine bay and watched to see if it would cut off. I waited about 5 minutes and the compressor never cut off. Both radiator/condenser fans stayed on too. I finally got tired of it and went inside.
I have a '92 Maxima that I overhauled a couple of years ago and it's not inspected right now so I'm not driving it. I pulled the compressor relay out of it and swapped it into this car. I'll see how the car does with it tomorrow.
You may have a clutch gap problem where the gap is slightly too wide.
Some of these cars had a magnetic sensor on the clutch that was used to compare compressor speed with engine speed. You can see that bracket sitting on top of the clutch if you have one. If that sensor gets erratic, you will have the exact symptoms you are posting. Check this out.
The gap increases over time due to wear of the contact surfaces of the clutch plate and pulley.
Other ways to diagnose a clutch issue are to test if the coil is getting power when it should be engaged (but is not), and to tap on the clutch plate with a suitable tool to see if that makes it pull in. This must of course be done with great respect for the moving parts.
If your car has an rpm sensor and lockout system like Nick said, it will cut power to the coil and lock out the compressor until you turn A/C off with the button and turn it back on. Usually these systems will cause the light on the button to blink while in lockout mode.
Sorry this has taken me so long to get back to. I've been pretty busy and haven't had a chance to check it with the gauges until today.
I have been driving it since my last post with a temp gauge at the center vent. I guess my previous characterizations that the a/c will occasionally get "as cold as I'm accustomed to" were wrong. The temp gauge shows the car never gets below about 50 degrees at the center vent. I know for certain this car used to work it's way down to nearly 40 degrees at the center vent (while driving of course). Currently, when I'm out driving the car and watching the temp gauge at the center vent, the car pretty much is always within the range of about 50 degrees up to the low 60's.
Now, low 50's is adequate, of course. But the problem is that the temp will only briefly hit 50 degrees, then quickly rise up to about 62-63 degrees and stay there for long enough that the cabin starts to get warm and I feel like I'm about to start sweating. If I recall correctly, this car used to have an operating range at the center vent about 10 degrees cooler. Meaning, it would work its way down to about 40, then rise up to low 50's before working its way back down to 40ish.
Today I was able to put the gauges on it. It was about 81 degrees outside at the time and 64% humidity according to the local news.
I put the gauges on with the car off and the low side read 85 PSI and the high side read 90 PSI.
Started the car up and let it idle with the a/c on, compressor immediately engaged, and low side was 32 PSI and high side at 170 PSI. Center vent temp worked down to about 55 degrees and stayed there. Both radiator fans stayed on. The pressure gauges weren't bouncing or anything. Compressor stayed engaged the whole time I was letting it idle (probably 5 minutes or so). After about 5 minutes of constant compressor engagement at idle the pressures were 30 PSI low side and 160 PSI high side.
I then raised the engine speed by manipulating the throttle cable to about 2000 RPM (maybe a little higher - I couldn't tell for sure as I had to guess by the engine sound), low side pressure worked down to about 20 PSI and high side pressure went up to about 220 PSI and then the compressor disengaged. I did this a few times and though the pressures were never identical to 20 PSI low and 220 PSI high, they always seemed to get to about that same range with the engine speed raised before the compressor would disengage.
Pressures at idle with the compressor engaged were always about 30ish low and 170ish high.
Do these pressure readings indicate any obvious problem?
Apparently the compressor is disengaging due to evaporator temperature, so it is getting as cold as the controls will let it. The refrigeration loop seems fine. Check for reheating from the heater.
When you say check for re-heating from the heater, what exactly am I looking for? Do you mean something like the levers/flap that control the air mix?
Edited: Sun June 09, 2013 at 8:12 PM by James89dx
Any other input? I checked the air-mix door/flap and it's closing completely between hot and cold
The pressures mean very little. The system should be recovered, evacuated and then recharged with the correct amount of refrigerant for this system. This will require the use of professional equipment...no cans....and not using pressures to determine charge rate...this procedure will simply not work. Re test the system and post pressures. The first and most important aspect of a performance concern is to know that the system is properly recharged. The cycling could be the result of an undercharged system and the resultant low temp of the evap. The posted reference to lack of cooling performance (compare past to present) and the age of the vehicle tends to point to a undercharged system.
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So professional equipment means that I would need to take it a shop I guess. I really hate to do that because in my experience they always just claim your compressor is bad and then want to charge you a grand to replace the entire system nearly. Sadly that seems to be the norm. If I had a known truly capable/honest shop that I could trust to truly diagnose it instead of the blanket "bad compressor" BS I wouldn't hesitate to take it to them.
Pardon my ignorance, but if you said the pressures mean very little, what good is my posting the pressures after having a shop evacuate and recharge the system? Is it just so that it's a known good starting point?
Edited: Wed June 12, 2013 at 2:16 PM by James89dx
Well I did end up adding about 3/4 can of refrigerant which did not fix the issue. So after another week of researching it and a thread on a Maxima-specific forum with no good leads/answers, I decided to break down and have a shop look at it. I had my brother take it to work with him (he's a PepBoys store manager) and had the service tech look at it. Since my brother is the retail store manager I had pretty good confidence they wouldn't blatantly rip me off but I still just don't like having to have a shop do anything on the car. Thankfully my brother was able to make them knock down the "book time" to ACTUAL labor time. Anyway, the tech evacuated and recharged the system and it was still displaying the symptoms I described above. He eventually determined the evap temp sensor was bad (he actually referred to it as a "thermistor" but I've only ever heard of newer Maximas have those). It's about a $90 part from Nissan.
I just got the car back last night and today will be the real test driving it around in the nearly 100 degree heat. We shall see
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