Just bought this car about a month ago. Noticed when test driving that it was not cooling initially and then I saw the temp control was on hot, so I ignored it. Turns out anytime the car has been sitting for like 5 hours or more, the A/C blows warm for a very long time. Suspect it might be a bad blend door control. Don't know if it's motor or vacuum controlled. Anyone experience this before?

It's a servo motor, late model Nissans don't use any vacuum controls. But I'd try an evac-recharge before jumping to any conclusions, it may just be low on refrigerant and it's taking the evap a long time to get cold. If you have a scanner that can stream system pressure from the ECM, it's easy to check. The sensor should read above 2V with the compressor running (usually 2.25~2.50V in a healthy system). If it's lower then chances are it simply needs a charge.

No scanner capable of reading system pressure. I considered just evacuating and charging initially because it's a salvage restored car, so it's likely that the A/C system has been opened up, it just acted more like a blend door issue. Thanks for the input. I'll have to find out if there's a way to see the blend doors position before I evac it.

Nico has the FSM for your ride, the HVAC Control section is here:
https://www.nicoclub.com/service-manual ... %2FHAC.pdf

If it's an Auto system then you can easily tell if it's a mix-door issue because there are separate Driver and Passenger servos. Put it in split mode with the same temp setting on both sides, if they both do the same thing then the servos are fine and your problem is elsewhere.

Looked at this today. Pulled the glove box and watched with a flashlight to see if everything was working. Found that the passenger side is all ducting controls and that all worked great. Looked at the driver side and found that the blend motor was behind the gas pedal area under the dash. Switched from HOT to COLD a number of times and it worked like a charm.

Figured you must be right on the refrigerant level. Opened up the system slowly and leaked it out. Only had 95PSI on the system (at rest) before I opened it up. Didn't take long before it was empty. I realize it's only 1.5 cans, but it didn't even seem like that. Evacuated the system and put 17-18oz of R134 in it. Had to work on a bunch of other stuff, so I won't know if it fixed it until tomorrow afternoon, but I'll post up what I find.

No change at all after the evac and recharge. Same exact issue... takes 3-4 minutes at around 90 degrees before the air feels anything besides hot coming out of the vents and it never got cooler than 58 degrees at the vents. I've lived in Phoenix for almost 30 years so I know what to expect. Even my 88 Mustang with hundreds of thousands of miles and a used 30 year old Ford compressor and old hoses that I converted over to R134 from R12 kicks butt over this thing. Typically, it'll cool the vent air within 30 seconds or less at 90 degrees out and the vent temps hit high 48-50 degrees on MAX.

Other ideas? Could the blend door be broken where some of the hot air is coming through all of the time even though the blend motor is moving?

That's possible. The Mix Doors on Nissans are almost all sliding types, with a setup similar to a rack and pinion. If the pinion jumps a tooth then the door ends up cracked open at one end of its travel. That doesn't happen often, and assuming the pinion isn't stripped, you can fix it by manually moving the door to the full cold position with the servo out, then dialing the control to full cold, then reinstalling the servo. It's also possible the splines on the door and servo have jumped, but that usually means a new HVAC because it's almost always the door splines that give out.

Looked into this further this morning. Temp was around 72 degrees in the garage before starting the engine. First, I pulled the driver floor duct off to get a good look at the blend door functionality. Everything appeared to be NORMAL (see video below).

https://youtu.be/I7wOinYPpFc

I then started the vehicle up and let it run for 3-4 minutes before taking video of the vent temp, engine temp, and other aspects. Vent temp took about 7 minutes to drop to even 52 degrees and that's with a car that has been in a garage in the shade for hours (see video below).

https://youtu.be/FJVAdBWp8tc

I continued to let the vehicle run until around 12 minutes, then I took some more footage. By that time, the vent temp had actually climbed back up to about 58 degrees even with the system having been on MAX the whole time (see video below).

https://youtu.be/ubZMzxjjVaw

Had to call it for the morning, so when I left around 10AM just 30 minutes later, I drove 2 miles to the freeway and then 7 miles on the freeway. The vent temp never got any better than 53 degrees (see video below).

https://youtu.be/qcmLXecO2lo

Another thing that I noticed the other day when driving around with outside temps around 100 degrees is that the temp in the vents would cycle from slightly cool, to warm/hot on and off every couple of minutes. This was on a short trip on surface streets, but this was running on MAX air and I am certain that the compressor clutch was engaged the whole time. This got me wondering if the problem might be a bad expansion valve?

A friend of mine that went through HVAC school 10 years ago (he never worked in the industry), thought that maybe it might be caused by contamination in the system? He said that I should see high pressures with the system off if contaminants are the cause. Does this sound like a possibility or unlikely?

Any additional help is greatly appreciated!

Sure, that's possible. The only two contaminants usually seen are water (causes intermittent freeze-ups in the evap or TXV, usually after the system has been running awhile) or pellets from a broken dessicant bag in the Receiver/Drier. If it's the latter the entire system will need to be disconnected and cleaned out, but usually pellets lodge in the TXV and cause a complete loss of cooling.

One other thing you might check for is a stuck swash plate in the compressor. The compressor on your Sentra (and most other late model Nissans) has a variable piston throw controlled by a solenoid with a PWM signal from the IPDM. The solenoid controls a swash plate that lengthens or shortens the piston throw so the compressor moves more or less refrigerant depending on the cooling load. When the swashes stick it's usually at the bottom with the compressor moving minimum volume, so the A/C doesn't quit, it just works crappy. There's a super-easy test for a stuck swash. Put the system on Max A/C and the fan on minimum speed, then take the outlet temp. Then do the same thing with the fan speed set to max. If it produces good cold with minimum fan but stops cooling at max fan, the swash is stuck at minimum throw and you need a new compressor.

VStar650CL wrote: ↑

Sun May 29, 2022 5:56 pm

Put the system on Max A/C and the fan on minimum speed, then take the outlet temp. Then do the same thing with the fan speed set to max. If it produces good cold with minimum fan but stops cooling at max fan, the swash is stuck at minimum throw and you need a new compressor.

Hey, thanks a lot! I'll check this out in the morning.

Well, I ran the vehicle for 8-9 minutes before I started recording video. At that time, the garage temp was about 85 degrees, yet the temp in the vent was only 65 degrees even with MAX air on the whole time.

https://youtu.be/HESnkiYf6z8

At around 15-16 minutes of run time on MAX air, I tested the fan at both low speed and high speed, neither seemed to have any direct impact to the temp at all. Coldest it got was around 61-62 degrees even by the end of the video which is over 20 minutes of run time.

https://youtu.be/xy8Ws8IB428

Frustrated, I put the manifold kit on it with the engine off to see what the static pressure was. My buddy said that a higher at rest pressure is usually caused by contaminants in the system. I read 125PSI for static which is, if anything, might be a bit low. Outdoor shade temp was 85 degrees, but under hood was probably at least 125 degrees which means it should be upwards of 175PSI.

I started the car back up, cranked the MAX air and found that the LOW side dynamic was very high between 68PSI-95PSI, meaning the pressure was swinging between those values and typically when the pressure was low on the LOW side, the pressure on the HIGH side was greater. The HIGH side dynamic values were between 145PSI-180PSI.

https://youtu.be/Bf94OOZGeqw

So my LOW pressure side is far too high and the HIGH pressure side is probably a little low because the LOW pressure is too high. Looks like this can be caused by either a weak compressor or an expansion valve stuck open?

"Weak" compressors are almost always a result of bad reed valves and will usually give you a shaky high-side needle, but otherwise the symptoms are similar to a stuck swash (for exactly the same reason, limited refrigerant volume). It could also be an internal leak in the compressor (basically bypassing) but that generally makes the compressor noisy. Since you didn't see any temperature drop with lower fan speed and didn't mention any clatter, I'd say the TXV is most likely.

Well I replaced the TXV, evacuated the system, and charged it, but weirdly, it worked the best with only about 9 oz in the system. The pressures were good and the vent temp was around 40 degrees. I'd never seen this car perform this well in the last month since I've owned it.

https://youtu.be/W9jijgv3Erc
and
https://youtu.be/XeG_mAwQ1yc

I continued to add refrigerant until the can was empty (12 oz). By that time, the vent temp came up to around 43 degrees from 40. I already had a bad feeling... Even still, I put the next can on, purged the line and opened the low side valve back up. The first oz went in pretty quick. I went and checked the vent temp and saw that it was climbing up still, but I continued to add refrigerant knowing it was only at 13 oz or so. Took about 5 minutes and a hair dryer to get another oz in the system and then it kind of stalled. Now the low side pressure had come up a bit and the vent temp had climbed up considerably.

https://youtu.be/BxzI6pJuS_k

I shut the car down, took a shower and then hit the road. The car started blowing semi-cool air within 30 seconds or so (which it never did in the past), but it still wasn't cold like a normal car. We drove it for 6 minutes on surface streets before we had our first stop. By that time, the vent temp was down to about 45 degrees. Again, this is a feat that this car has never performed before. We parked the car for 30 minutes and then drove another 4-5 minutes before the next stop. We got to around 45 degrees by the destination, but I left it idling in the parking lot for almost 10 minutes and by that time the vent temp was up to 62 degrees. Keep in mind that it's only about 90 degrees outside with 11% humidity. It's definitely better than before, but not what it should be. Could this be a weak compressor?

Starting to wonder if I'm dealing with multiple issues. I'm thinking that this system had a problem before I bought it and someone tried to fix it and only made things worse. I'm basing this on the fluorescent yellow oil that I'm seeing in this system. To me this means that someone had a leak (probably a very slow one) and they stupidly added a can of oil charge so that they could try and locate the leak, but in the process they may have overfilled the system with oil which is now creating a headache for recharging.

Additionally, I noticed the bottom port of the TXV was very lightly blackened. I don't know if these Nissans are like Fords and if that's the black death or if this is somewhat normal, but I'm wondering if that's an indication of a worn compressor as well. If this is true, does this mean that I need the system completely flushed, compressor replaced, evacuated and charged? Are these Nissans typically this bad at 59K miles?

Black in the system is bad news on any make, not just Fords. It's oxidized alloy, the same stuff you get on your rag after polishing aluminum wheels. It comes from too much moisture (usually standing water) spending too long in the system. R134 and R12 both turn acidic in the presence of water, and it gradually eats the plumbing if it isn't removed. My guess is the previous owner either topped it frequently without evacuation or drove it for some time with the A/C inop and open. Evacuation won't get all of it if there's a major amount, it will need to be flushed and the Receiver/Drier replaced. My guess is there's a lot of it in there and that's why the system won't function with a proper charge amount. Combined with the water, the system ends up overfilled and ineffective.

The dye is a different story, I'm pretty sure a '14 came with it from the factory. Check your capacity tag, if it's green then the car came with dye, if it's black then the dye was added later.

Not surprised by your response. I figured that it was going to be bad news.

Interestingly though, with a 95 degree temp outside, the vent temp got down to 38 degrees at freeway speeds after about 5 miles of travel. Once we went back to surface streets for 3-4 miles, it came up to about 43 degrees. Parked for about 15 minutes and by 5 minutes in, the temp had climbed to about 62 degrees and that's where it stayed until we started down the road again.

Considering that the Nissan compressor isn't that great anyway (from what VStar650CL said), is there a particular brand of aftermarket compressor that is known to be a very reliable replacement or should I just do as I have in the past and buy a low dollar NEW compressor, condensor, drier, and hoses on ebay? I've found everything for less than $300 total.

My customers have had decent luck with Four Seasons. However, if the problem is water, it's your Condenser that will need to go. The Receiver/Drier is part of it. Maybe the compressor too, but that's a maybe.

Decided I didn't want to continue with this since it's 105+ degrees everyday now and been driving my wife's car for the last 2 weeks while she was out of town. I bought a condensor and compressor, flushed out the evap and hoses with Methanol, evacuated it on and off for 6 hours yesterday and left under vacuum overnight. Sucked it again for 30 minutes this morning and charged it. System is hitting 45 degrees in the vents at idle and 36 degrees driving on surface streets with it at 105 degrees outside. The air starts cooling within seconds even when the car's been sitting in the sun for hours.

The old compressor was a Sanden and it was made in USA. This was already replaced then, wasn't it? It looked like it had been on the car a while too. Additionally, the condensor was missing the upper left hand mounting bolt, so that's been replaced before. Probably from the front end collision that occurred at some point...

Thanks for all of the help! I'll keep you posted if things go south in the next few weeks (fingers crossed).

AZSentra wrote: ↑

Tue Jun 21, 2022 8:36 pm

The old compressor was a Sanden and it was made in USA. This was already replaced then, wasn't it? It looked like it had been on the car a while too. Additionally, the condensor was missing the upper left hand mounting bolt, so that's been replaced before. Probably from the front end collision that occurred at some point...

Thanks for all of the help! I'll keep you posted if things go south in the next few weeks (fingers crossed).

Yep, that certainly doesn't sound OE. Glad it's fixed, though. You're welcome, and happy (cool) motoring!