95 Q45 AC Question

[rsiwicki]

okay....until about 2 weeks ago the only hot thing with my car is the rubber burning off the rear of my car. Now the whole entire car is getting hot.

I am having an on/off AC problem. The AC seems to work for one minute and then next minute does not work. I just had the AC lines checked for pressure as I thought this was the problem that I had a small leak and line pressure was low causing the compressor to shut off until pressure builds back up. This is what they said:1. The line pressure was a little low, but not significantly out of the operating range and so they added a small amount of R134a to get it back to proper pressure.2. AC compersor was making a very very small noise, but should not be the cause of the problem and seemed to be operating fine when it did kick on.3. Something about an evaporater valve? was not opening up when they were testing the charge in the system and they thought that it would open up easier after running the car around town a little longer after adding R134a to the system.

The told me to drive it around for the next week and see if there was an improvement after topping off the charge to the proper level, but there was no difference. It was not working on the way to lunch, but on the way back it had started to work a little, but no different from how it has preformed over the past two weeks. It was a short 3 mile trip to the restaraunt. This all of a sudden happened about 2 weeks ago, then again it really did not start getting hot until 2 weeks ago either.

When the AC does work, it is cold, but when it does not work it just blows plain old regular air. Also it seems to take a few minutes for it to blow cold air after initially starting the car and for some reason the air feels colder if I redline the car.

btw...AC system is all original with 152,000 miles.

Anybody have a suggestion as to the problem? I don't want the repair shop to sell me something that I don't need fixed that is not the cause of the problem.

[elwesso]

Theres an expansion valve that is known to go bad, that could be the culprit...

[rsiwicki]

yeah...I think it was an expansion valve he said? but my Spanish Auto translation is not all that good. The mechanic did not speak any English.

Is the expansion valve expensive or difficult to replace?

[elwesso]

Seems to me like its $100ish and i dont recall on how much labor is...

[DAEDALUS]

You need more info from the techs. "Line pressure was low". Is that on the high side or the low side? Makes a big difference. If high side then it could indeed be the compressor. If low side, then that does sound like the expansion valve--kind of. I've read of 2 instances on this board for expansion valves going bad, far more for compressors going bad. The odd thing is that once an expansion valve gets clogged, it usally stays clogged. If the dual pressure switch is cutting off the compressor, then the high-side pressure is beyond just a little low.

[rsiwicki]

thanks for the responses....I read through the archives and still don't really have an idea except that I think I can safely rule out the ac compressor is bad and evaporater. Looks like maybe an expansion valve, dryier, or maybe line pressure was gettting low enough to screw everything up. Either way....something is definitely switching the cooling function on/off as this morning was nice and cold, this evening was nice and cold, but mid day it was worthless as well as the first few miles on my journey home. I will try to find a better AC shop this week or next week to let them have a look see at it to see what is up.

I gather from the archives I should have the entire system flushed, expansion valve replaced, along with the dryier as preventative maintenance along with what ever else is wrong with the system. Is this correct and am I missing anything that also should be done as preventative maintenance?

[elwesso]

Yeah the system should be flushed... I think tech said his frist compressor lasted a LONG time, like 220k or something......

What I would do is take hte FSM in (or print the pages off if you have the version i have) and then they can determine whats wrong...

[DAEDALUS]

All AC systems work on the same principles, only the numbers change. No reason to ever pay shop rates to have them read up on how the system works. They should have the specs they need for what's different from car to car.Could also be water in the lines...freezing, causing a blockage, then thawing. Drier shouln't have anything to do with the immediate problem, but of course if it's old it's not soaking up moisture anymore. The only things that can interrupt the compressor relay once the AC is turned on are the pressure and temp switches. The only thing you can do on your own is keep your condenser clean to prevent the system from overheating. Doubt this is the case.Don't pay the labor to have the expansion valve replaced unless they're sure that's the cause. It's as much work as replacing the evaporator.

[rsiwicki]

thanks for the good & wise $$ saving advice. I will have them check it out and hope it is simple to diagnose & fix.

[CJQ45]

Did you figure out what was wrong?? I have a 03 maxima whose AC doesn't work. I checked the low pressure line - the pressure was alomost "0" I filled it with R134a, as soon as the proper pressure was obtained, I heard the AC compressor kick in. So I thought cool - got some AC - not the case.

Although the AC compressor is working - I still dont have cold air? I didn't check the high pressure line - but if that line was low, the compressor wouldn't have turned on. I still don't know what the problem is.

Any info. would be helpful

CJ

[SpecDRacing]

This is starting to trail off into another forum, but I'll try to help. The 03 maxima has a different control system, though it still uses the same horrible expansion valves. Look for these valves to go bad on the Armada, Titan, QX56, and other vehicles from Nissan.

Without having numbers infront of me, of what the preasures are int he system and as to what amount of R134a is in there, I cant help much. One thing I can say is that if you have too much R134a in there, the system will see the excess preasure, and shut down. So you might have actually added too much. Also, Nissan unfortunately has gotten very cheap lately with the sensors and components used in their vehicles. A metal shortage in Japan is hiking up the cost per unit, meaning more plastics must be used.......meaning DEAWOO's!! LOL Not that bad, but getting there.

Back to the A/C. Get the FSM and do the auto diagnosis procedure. Its going to be something like KOEO, within 5 seconds hit two buttons or tun some knobs and the system will go to a 6 or 7 step diagnosis. Each step will check different things such as mode door functions, sensor functions, comand functions, also temperature corrections can be made (if your personal thermometer reads 48 from the vents, and you have it set to auto at 50, you can adjust the reading by up to 5 degrees), etc. That last part might not have been available on the 03 maxima, but is available on some. Anyway, give me the codes it displays for each system. There will be one code that will always set. It will be for the "sun sensor". If its not broad daylight and high noon with your car in an open parking lot, you'll get this code. Dont worry, its not bad, its just used in recognizing that your car is getting blasted with ultraviolet light, which can heat the car up in areas far from the interior ambient temp sensor, meaning the car wont actually stay at 72 degrees when set to auto becaue that sensor will read differently than in other parts of the car.

Man, I've done some typing tonight! I hope this help, and its been a little while since I've played with the auto a/c systems. If you can get those codes, we can tell you whats wrong.

[CJQ45]

Thanks for the reply Mark!!

Ok heres the deal -- the 03 max had a faulty ambient temp sensor. The sensor itself was not bad - checked with a voltmeter - there was no volatage coming into the senor. Found out the problem - broken wire from the harness and fixed it - so the reading in the car was showing the actual temp (72 F) instead of --- ICY when it was 72F (boiling inside the car). I ran the check on the car - code 21 showed up for the ambient sensor (reading -22F by default). Once that was fixed there are no codes present - including code 25 (sunload) - I checked it under the sun.

So here is the deal - No codes from the car computer. The low presuure line is reading 25 psi (not over charged). I didnt read the high prssure line - but it should be good because the comprssor kicks in when I turn the AC on. Before when the low prssure line was reading 0 psi, the compressor didn't start - now it does. But heres the problem - no cold air??? What the deal?? No codes, pressures are good - the compressor kicks in - but no cold air??

What the deal????

[DAEDALUS]

Does the return line coming from the evaporator get cold and wet?

[rsiwicki]

its working better (I guess???) after the additional freon. Still takes way too long for it to start cooling on a hot day but at least it seems to be cooling constantly (not cutting off)

taking it to another mechanic soon.

[SpecDRacing]

Time to start cooling depends heavily on ambient temps and humidity. If it works by definition, then its fine. Sitting still in traffic or in a parking lot, the condersor wont recieve enough medium to release heat, but moving, it will. If its working, then its working. I know it sounds kinda crappy, but its best not to fix something that isnt broke. Hopefully this will help you some. Thank!

[DAEDALUS]

If the high side is low then it can be fixed. The compression of the fluid is essential to the movement of heat. The AC system is simply a heat pump. The higher the pressure, the more heat that can be removed inside the evaporator later in the circuit. Does spraying the condenser with water help at all? Does the aux AC fan turn on with the AC?

[rsiwicki]

Well....I was going to take the car at 8am to the mechanic but that did not work out after hooking up with a little sweet thing so maybe Monday I go.

It definitely is totally rpm related? as far as the cooling goes. I can turn on the car and let it sit at idle or come to a stop light at idle and cooling totally stops....then as soon as I start moving or rev the engine you can feel the temp drop almost instantly.

Something definitely broke on it the other day.....just got to figure out what as it was working fine until about 2-3 weeks ago. Now it is only marginal at best.

[DAEDALUS]

You're saying if you rev it in neutral at a stop the cooling increases? Again, try spraying a light misting of water on the condenser and see if it makes a difference.

[rsiwicki]

can you tell me where the condensor is??? sorry for my ignorance and laziness not looking up in the FSM.

Update...I just got done doing a 2 hour trip from Miami to middle of the Keys and back today (2 hours each way). The AC preformed ICE cold without any problems with outside temps at 90, sun beating down strong, cruising all the way down and back at about 40-80mph. The AC stopped working as soon as I got off the interestate into traffic in downtown Miami. You can literally feel the ac stop instantly. While at a stop light I put the car in nuetral and brought rpms up to 1,500rpms and it almost instantly started cooling again....you could literally feel the vent temp drop as soon as I brought the rpms up to 1,500rpm. While reving the rpms to 1,500 the ac was not super cold like when I was cruising on the interstate, but it was much cooler.

Any ideas??? I still plan on taking to mechanic sometime next week as I don't have time this week.
Modified by rsiwicki at 6:20 PM 5/10/2005

[elwesso]

Im thinking it could be the condensor.. If its not getting adequate airflow its not cooling as it should.....

Ill wait and see what Robert says, as IM not that knowledgeable about AC systems...

[911/Q45]

I'll bet the electric fan in front of the radiator and condensor has failed. That would explain cooling at speed, but not at idle.

[DAEDALUS]

The condenser is the radiator in front of the radiator. Is it possible to determine if the compressor is actually shutting off when the cooling drops? Can you hear the clutch disengaging and/or a change in idle speed/pitch?

[rsiwicki]

911/q45.......you hit it on the nail. My condensor fan is not working. Now the question is why it is not working. I tried switching the fuses and relays under the hood next to the battery but no response from the fan yet and the relay I switched them with (cruise control) seems to be fine. I can't for the life of me figure out what temp sensor harness I need to disconnect on the passenger side to trick the system getting the fan to turn on. Can somebody post a pic of the specific wires that I should disconnect so I can try this method out. My thoughts are that it must be the fan motor that is shot. I spoke with Wes in length yesterday and he gave me all the tips on how to do a test or two on the fan. My last resort would be to wire an inline fuse wire from the battery directly to the fan motor to see if that will get it moving.

Thanks again all for your help. At least it is not my compressor or anything else like that would cost major $$. I will follow-up with my posts after somebody tells me which harness to disconnect and afterwards post my results and difficulty of removing the fan. Hopefully it is not too difficult for a quick R&R of the fan.

[DAEDALUS]

Does the aux AC fan turn on with the AC?

Guess I should have been more descriptive? You can disconnect the fan harness just in front of it and jump the fan with 12V to make sure it works.

[rsiwicki]

sorry, I thought you were referring to the fan blower in the car.....my bad. so you are saying I can hook up a 12 volt battery from the grocery store and see if it starts to spin the fan??? sorry for my ignorance...I am very new at AC stuff.

[rsiwicki]

Ohhh....I almost forgot. I have been hearing lately this strange buzzing sound coming from somewhere under the hood while seated in the car after initially turning it on. Well when I was check the fan I heard this sound (short buzz for like 1 sec) again and it seems to be coming from the relay/fuse box next to the battery. Is this normal because I have never noticed this before and everything else seems to be working correctly???

[DAEDALUS]

You could buy a battery, but maybe cheaper to connect it to the car's battery with alligator clip wires or something like you said. Be careful to not short the battery!

Spraying water on the condenser will add another clue. Opinions vary, but I don't think the fan not working would make *that* big a difference in cooling. If you hotwired the fan and the cooling returned to normal at idle I would be surprised, but check it out.The fan is controlled by temp and pressure. If it works, and all wiring/fuses/relay are good, then probably pressure is too weak to turn on the fan, and would also be the reason cooling is not sufficient. Besides hotwiring the fan, you can try jumping the pins on the pressure switch connector under the battery (on the drier).All this is a lot of shadetree work to gather the same data the first shop should have been able to get from the gauges.

[elwesso]

But how is the cooling when moving at highway cruise (when airflow is plentiful) its ICE COLD but as soon as he stops (airflow is reduced) it gets warm again.. The condensor fan moves a LOT of air...

The RPMs wouldnt matter since the compressor uses the same amount of power (at full load) whether the car is moving at 60mph or just revving at 2000RPM

[DAEDALUS]

Still trying to gather data. Is the compressor even engaged at idle? That could be a cause.

[rsiwicki]

finally had some time to test out the condensor fan....I have never seen nor heard it run until tonight. I moved some relays around (already did this but did it again) and then about 10 minutes later after about 10 minutes of idling with AC set a 65 on high the condensor fan kicked on. I have driven the car in 90 degree heat here in Miami and popped the hood never to find the fan running so maybe I do have a relay that is bad. I can hear a very distinct buzzing sound coming from the relay area by the battery that buzzing that last for about 3 seconds that occurs every 5 minutes or so.....is this normal or is it due to a bad relay. The AC has been ice cold while moving and was ice cold while idling tonight which is a first but the condensor fan kicked on. How do I check if the compressor is kicking on during idling?