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Car only blows cold at night *UPDATE*

metalgod3082 on Thu April 29, 2010 6:39 PM User is offline

Year: 1999
Make: Nissan
Model: Maxima
Engine Size: 3.0L
Refrigerant Type: R134a
Ambient Temp: 80
Pressure Low: 50
Pressure High: 150

Background info: My car is a 1999 Nissan Maxima. A/C would work intermittently. It seemed to work fine at night time or on cloudy days (When I say work I mean it blows ICE cold air). During the day I could sometimes get it to work when I was stopped at stop lights by turning off the A/C and back on several times but then when I would start driving it would start blowing ambient air again. AC compressor always engages.

I brought my car to the shop to have them diagnose it. They told me my TXV (Expansion Valve) was stuck open. So I told them to discharge the refrigerant and I would fix it myself. Replaced the expansion valve and receiver/dryer. Added all new O-rings and lubricated them first. Pulled a vacuum on the system for 45 minutes which held fine. And recharged using 2 cans of refrigerant with UV dye (12.5 ounce cans).

My car is rated for 25 oz so should be just about right. Also added 2 ounces pag 46 oil to receiver/dryer. This was at night that I recharged my system. Drove it for a few miles and blew ice cold air. Seemed to be even colder than before. So I'm thinking that fixed it. Well drove it today it blows ambient air again. When I checked the pressures last night the Low pressure was around 50 psi and the high side was around 150. Any ideas what is going on?

Edited: Tue May 04, 2010 at 4:54 PM by metalgod3082

TRB on Thu April 29, 2010 7:11 PM User is offlineView users profile

Do you still have refrigerant in the system? Worked yesterday and not the next, sounds like a leak for starters.


When considering your next auto A/C purchase, please consider the site that supports you:

metalgod3082 on Thu April 29, 2010 7:30 PM User is offline

I'll recheck the pressures when I get home from work today but I'm pretty sure everything is sealed correctly as it held a good vacuum yesterday.

bohica2xo on Fri April 30, 2010 12:00 AM User is offline

Check the clutch gap, and condensor airflow.

Excessive clutch gap will cause the clutch to stop working when it is hot. When the air blows hot, open the hood & look at the clutch plate on the end of the compressor. It should be turning with the belt pulley. If it is stopped, you have either a bad clutch coil or too much air gap. Adjust the gap first & see it if solves the problem.

Poor condensor airflow will make the system quit at higher heat loads. Check the condensor fan(s) for operation, and clean the fins on the condensor. Be careful not to bend or flatten the condensor fins while cleaning. To check for condensor airflow problems, mist the condensor with a garden hose while running the A/C. If the high side pressure drops like a rock, you have airflow issues.


"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

metalgod3082 on Fri April 30, 2010 2:17 AM User is offline

I'm a little confused on the air gap thing your mentioning. I have looked at the compressor and everytime I've looked at it, the middle part is spinning. I will try misting the condensor and see what happens. Will try it tomorrow morning and get back to ya. Thanks for the help!

NickD on Fri April 30, 2010 8:28 AM User is offline

Mean distance between the hub and the pulley when the clutch coil is disengaged, can range from 9 to 30 mils, for your vehicle, 20 mils is fine. Adjusted by removing the hub and either adding or removing shims.

You don't mention your climate control, a solar sensor on auto climate control systems can be your problem, it knows the difference between day and night. If temperature changes are the problem, can also be electrical as well. Increasing temperatures due to expansion can open what should be normally closed circuits.

Like to hot wire the clutch circuit first with erratic problems with a remote starter switch and gauges attached to be assured the problem is not mechanical within the system, rare to find erratic problems here unless working with a variable displacement compressor which you do not have.

If your compressor is not rotating, and your vehicle is warm, of course your expansion valve would be wide open, its suppose to do that. It only closes when the evaporator gets ice cold. Also have a dual function switch that limits compressor operation between 40 and 430 psi, if the pressures are beyond this range, your compressor clutch should not engage. But since this is also an electrical circuit, corrosion can be a problem. Poor condenser airflow can also cause real high pressures, in this case, your dual function switch is preventing your system from blowing up.

mk378 on Fri April 30, 2010 8:49 AM User is offline

Is it a variable displacement compressor, like a SD7V16? The AMA website doesn't list the compressor for that car. It seems that your compressor one way or another gets to a state where it will turn but not pump like it should. Variable compressors are particularly bad for that, they get stuck at zero or near zero displacement. The cure is generally a new compressor.

At 150/50 there should be some cooling (far from ice cold, but not ambient either) though. Is the suction pipe staying cold? If the suction pipe is cold but the air from the vents is not, there is some sort of reheating problem in the cabin.

Edited: Fri April 30, 2010 at 8:52 AM by mk378

metalgod3082 on Fri April 30, 2010 4:53 PM User is offline

Ok did a few more tests today. Rechecked the pressures, I think I had the pressures incorrect the first time as I didnt let it sit for a little to stabalize. I'm getting 68 for the low and 125 for the high. I let it sit like that on max A/C for 10 minutes and it stayed the same. I tried misting the condenser with the garden hose and all the pressures stayed the same. I checked the inside temp with a meat thermometer and its blowing really cold at 48 degrees. The thing is its a cool and cloudy day out today so It seems to be working fine but I know once I start driving and it becomes a little bit hotter outside it will stop working. Those pressures dont seem right do they? Do you think my compressor is shot?

bohica2xo on Fri April 30, 2010 10:39 PM User is offline

A full load test will answer that question.

Doors open. Cabin fan on highest speed. Connect your gauges.

Run engine @ 2500 rpm for 5 minutes. While the engine is still running 2500 rpm after 5 minutes, record the pressures & post them here.


"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

NickD on Sat May 01, 2010 5:02 AM User is offline

68 psi on the low side with R-134a is only capable of producing a maximum cooling of 67*F at the vents at a 100% heat transfer rate that is near impossible, should be even warmer than that. 48*F is not even possible with those pressures. Something here is amiss.

metalgod3082 on Sat May 01, 2010 1:27 PM User is offline

I know that's why I'm so confused. I'll recheck again and post pics of the gauges and the meat thermometer.

mk378 on Sat May 01, 2010 4:46 PM User is offline

Are you using the manifold properly? The hand valves on the manifold need to be CLOSED while taking pressure readings.

metalgod3082 on Sat May 01, 2010 8:16 PM User is offline

Yes I'm using them properly. I have the valves closed and the quick connect knobs closed. Then I connect them to the hi and low side. Start my car and turn the a/c to max cooling and fan. Then I open the quick connect knobs but leave the knobs near the gauges closed. Let it sit for few minutes and those were the numbers I was getting.

metalgod3082 on Tue May 04, 2010 4:59 PM User is offline

Ok did some further testing today. Seems I may have had the pressures wrong in my previous post. When I tested today my low was around 95 and my high around 100 but then I closed the quick connect valves and reopened them and then I got different readings of 47 for the low and 175 for the high. I believe these are the correct readings. So with these pressures my A/C was getting down to around 60 degrees. The Low side pipe is very cold. Now I revved the engine to 2500rpm for 5 minutes and right away I could see the temperature rising and it got up to about 90 degrees which is the ambient air temp. Also the low side pipe lost its coldness. The pressures all stayed the same of around 47 for the Low and 175 for the high. They may have fluctuated about 1-2 psi. Think this is a compressor issue? Any ideas? TIA for the help!

knightgang on Tue May 04, 2010 8:02 PM User is offline

When the temp rose up to ambient, that would have been the perfect opportunity to mist the condenser with water and see if the temps fell again.

With the pressures not changing, I think that you are misusing the guages. The valves on the quick connect need to be in a position that depresses the valves on the ac connectors to be able to continuosly read pressure. When you "closed them and reopened them" and got different pressures than before, I would say that you need to "close them" according to your terminology to get accurate readings. I think you "closed them" and allowed the proper pressure at that time to be read, then you "reopened" them and you trapped that pressure reading in the guage, therefore the pressures never changed.

I had this same learning curve on my guages when I first got them. Now I KNOW how mine work...

Good luck, keep posting and learn along the way.

metalgod3082 on Tue May 04, 2010 9:23 PM User is offline

Thanks for the reply! Definitely agree there is a learning curve to these gauges but I think I have it correct. At first I thought all the way clockwise was to shut it and then all the way counterclockwise was to open it (or where it depresses the valve to allow the refrigerant to come through). Well when I changed my expansion valve and then tried to pull a vacuum and refill it, I could not get the refrigerant to go into the system. I soon figured out that the knobs on the quick connect have to be kinda in the middle where they are a little loose to the touch and not all the way counterclockwise where its tight. Once I did this the refrigerant quickly filled the system. I hope this makes sense. So I do believe they are in the correct position.

Now this is what is kinda strange. These are the steps in which I connected and tested things today:

First of all I connect the quick connects and opened them up to get the static pressures. They were about 95 psi both High and Low. So with them open I started my car and and turned on the A/C. The Low side dropped to about 85 and the high side raised to about 110. So at first this is what I thought were my new pressures to go off of which was different then the pressures I got a few days ago when I tested. So I decided to close the quick connect knobs. When I did this the pressures dropped to the 47 and 175. I then reopened the quick connect knobs to where they were before I closed them and the pressures stayed at 47 and 175. So now the knobs are exactly where they were when it was reading 85 and 110 but now its reading 47 and 175. So which ones do I go by?

P.S. Sorry for the long read but I am really broke and living in AZ and its starting to get in the 90's here. I know I'm capable of replacing any part of the A/C system its just the issue of diagnosing it and determining what is causing this. The shop that I brought it to said my expansion valve was stuck open and that the compressor may be bad as well. They said they needed to replace the expansion valve first for $450 and then they would know if they need to replace the compressor. I dont really feel like trusting this shop so any more advice is much appreciated!

metalgod3082 on Tue May 04, 2010 9:35 PM User is offline

Man, I think I just figured out the problem. I found the manual online and it says to turn the quick connect knob clockwise to open it. I think I had it all backwards. Let me check the pressures again and get back to ya guys! Sorry.

mk378 on Tue May 04, 2010 11:04 PM User is offline

That's how couplers typically work, after coupling onto the fitting turn the knob on top fully clockwise to open the valves.

Also while you're out at the car see if you can read the nameplate on the compressor and get the model number.

metalgod3082 on Tue May 04, 2010 11:11 PM User is offline

I've been on and verified this would be the one I would need|GRP60000_613365928___

Would be able to get it for $211 with coupon code if that's what it comes down to. Also how much should I pay to have the refrigerant taken out so I can work on my A/C? I paid $40 last time.

Edited: Tue May 04, 2010 at 11:16 PM by metalgod3082

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