AC is Struggling with Cold Air

493 Views 9 Replies 7 Participants Last post by smj999smj, 1 d ago

altramarine

Good day,

The warm weather is upon us and the AC in my 2007 X (manual transmission) is not happy.
Behavior:

Once AC is turned on, on coldest setting, the cold air comes through for a few minutes and then gradually becomes warmer.
The compressor kicks in and stays up for around 5 seconds before going off and then kicks in again in 20ish second. During the ON time the air becomes slightly cooler but not cold. It is as if the compressor is struggling to stay on.

I noticed this behavior last year. However, I was distracted by a different simultaneous issue where the AC compressor would only turn on on 1st setting as described here. Thanks to this and other forums, that issue was resolved by replacing 27150-5Z000 Blower Motor Resistor.
In addition, my mechanically inclined friend had me get the AC refill kit form Walmart. He used majority of that kit to top up the coolant but that did not solve my original issue.

Crawling the web, I came across this video that closely describes my AC issue. The gentleman supposedly fixed this by replacing a sensor that is known as Sunload Sensor / Thermistor / Evaporator Temperature Sensor. I found that part on a few websites that are compatible with 2007, like this or this.

Based on my description of the problem, do you think it might be:

Thermistor
Compressor
Condenser
Other suggestions?

All of these parts are the originals since 2007. Perhaps they had enough

Thank you for your time!

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Just a Hunter

· #2 · 1 mo ago

Bring your Xterra to a qualified mechanic and inform them in the past your friend attempted to recharge your ac with a kit.

There are several issues which may be at fault including the possibility your ac system is overcharged.

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RamTest

· #3 · 1 mo ago (Edited)

There is little chance it is the sunload sensor unless it got damaged. That is there to prevent the evaporator from icing up which it clearly would not do in a few seconds, with warm air passing through it.

As a total hack procedure, just randomly adding a can of refrigerant without knowing how much is already in there creates its own problems. That procedure can give you acceptable results if the system is empty (without pulling a vacuum). It will leak out until the leak is fixed, but it will give cold air for a period of time. Add some leak detector at the same time, and you will find the leak.

If the extra can of refrigerant creates an overfill condition, the a/c cycle can't function. There MUST be sufficient expansion space in the system for the refrigerant to boil off, which it can't do if its overfilled.

So, at this point, you'll need to attach a manifold gauge to read the pressures. Since you've had several problems with this system that evidently are not resolved, it might be worth the money to bring it in to an a/c shop.

EDIT: If you insist on trying this on your own, the sunload sensor (thermistor) is directly behind the glove box on top of the heater box. Those are about $50. Gauges and vacuum pump can be bought at Harbor Freight or rented for free from Autozone. Two 12oz cans of R134A will fill the system from empty, $10 each. Protect your eyes.

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JZXatv

· #4 · 1 mo ago

I had a similar issue, last year it was completely remedied by them( a Shop) draining and refilling the system at, cost just under $100 for everything. Hasnt been this cold since I have owned it. Just tested the other day and still cold. This was also after a friend suggested a kit.

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altramarine

Discussion Starter · #5 · 1 mo ago

Just a Hunter said:
Bring your Xterra to a qualified mechanic and inform them in the past your friend attempted to recharge your ac with a kit.

There are several issues which may be at fault including the possibility your ac system is overcharged.

Thank you, I know I should have gone down that road from get go

RamTest said:
There is little chance it is the sunload sensor unless it got damaged. That is there to prevent the evaporator from icing up which it clearly would not do in a few seconds, with warm air passing through it.

As a total hack procedure, just randomly adding a can of refrigerant without knowing how much is already in there creates its own problems. That procedure can give you acceptable results if the system is empty (without pulling a vacuum). It will leak out until the leak is fixed, but it will give cold air for a period of time. Add some leak detector at the same time, and you will find the leak.

If the extra can of refrigerant creates an overfill condition, the a/c cycle can't function. There MUST be sufficient expansion space in the system for the refrigerant to boil off, which it can't do if its overfilled.

So, at this point, you'll need to attach a manifold gauge to read the pressures. Since you've had several problems with this system that evidently are not resolved, it might be worth the money to bring it in to an a/c shop.

EDIT: If you insist on trying this on your own, the sunload sensor (thermistor) is directly behind the glove box on top of the heater box. Those are about $50. Gauges and vacuum pump can be bought at Harbor Freight or rented for free from Autozone. Two 12oz cans of R134A will fill the system from empty, $10 each. Protect your eyes.

Cheers for the response. We used this kit to get it to the green zone using the included pressure gauge meter. I don't remember now but my friend said it was slightly low before we started.
I was really tempted to try the thermistor replacement as it is the cheapest DIY route(thanks for the instructions). BUT based on what you said, it is unlikely the thermistor so might need to drop $$$ and have it looked at a shop.

JZXatv said:
I had a similar issue, last year it was completely remedied by them( a Shop) draining and refilling the system at, cost just under $100 for everything. Hasnt been this cold since I have owned it. Just tested the other day and still cold. This was also after a friend suggested a kit.

Many thanks. Yep, looks like the general consensus to bring it to the shop

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Eurow

· #6 · 13 d ago

altramarine said:
Thank you, I know I should have gone down that road from get go

Cheers for the response. We used this kit to get it to the green zone using the included pressure gauge meter. I don't remember now but my friend said it was slightly low before we started.
I was really tempted to try the thermistor replacement as it is the cheapest DIY route(thanks for the instructions). BUT based on what you said, it is unlikely the thermistor so might need to drop $$$ and have it looked at a shop.

Many thanks. Yep, looks like the general consensus to bring it to the shop

Do you have any update on this? My X is having some similar symptoms currently.

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curveball3110

· #7 · 9 d ago

Just a Hunter said:
Bring your Xterra to a qualified mechanic and inform them in the past your friend attempted to recharge your ac with a kit.

There are several issues which may be at fault including the possibility your ac system is overcharged.

For anyone who comes across this in the future-

Bingo. Those guages that come on the kits are a joke. Plus, they don't account for what pressure the vehicle should have in the system anyways (there is a high and low pressure line).

On top of that, the recharge bottles come with stop leak, which would be great if tolerances weren't extremely small in a/c systems. The stop leak can and will plug up the system over time.

The a/c system is a completely closed loop, so if it's low on refrigerant the question would be why. It doesn't just burn off like oil or overflow like coolant. Best way to know is take it to a shop who will evac the system and fill with r134 mixed with dye. After a week you'll take it back and they'll use UV light to trace where the leak is coming from. From there it's downhill sledding. You can choose to do the repair yourself but I'd have a shop recharge it once done. It's near impossible to buy r134 retail without stop leak I'd imagine due to gov't regs. They didn't sell it at all in CA or Hawaii from my experience.

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smj999smj

· #8 · 1 d ago

Nissan A/C systems come with dye in it from the factory. If you have a black light, you can look for signs of leaks. Most common areas are the A/C condenser and anywhere there's a connection, like the pipe to the compressor (which is usually an "O"-ring failure). Another place to look is at the press fittings between the rubber and metal hose and check the water draining out of the evaporator. If you see dye in the water draining out of the evaporator, you'll likely need a new evaporator. The front seal of the compressor is another potential spot for leaks; use the black light to check the front area of the compressor, behind the clutch. More than likely, you have a slow leak. Only way to confirm that is with a set of A/C high and low side pressure gauges. Also, it's more than just what the pressure readings are; ambient temperature and humidity also have to be taken into affect. This is all explained very well in the factory service manual for your vehicle in the A/C chapter. NICO Club's site has free, online manuals.
FYI, to replace the thermistor, you have to remove the entire dash and heating/cooling unit. You are supposed to remove the dashboard to replace the sunload sensor, but I believe some people have found a quicker method?

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Eurow

· #9 · 1 d ago

smj999smj said:
FYI, to replace the thermistor, you have to remove the entire dash and heating/cooling unit. You are supposed to remove the dashboard to replace the sunload sensor, but I believe some people have found a quicker method?

I can 100% confirm that replacing the expansions valve and sunload sensor can be done without removing the dash. I replaced both this past weekend. Expansion valve can be accessed from the engine bay, just bellow the heater core coolant lines. The coolant lines do not have to be removed but would offer more working room if so. The sunload sensor is accessed by removing the lower and upper glove boxes. The sunload sensor can be swapped out in about 10 minutes using only a phillips driver for 9 screws.

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smj999smj

· #10 · 1 d ago

Expansion valve-yes. Not the thermistor, which is pushed into the evaporator core.

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