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Jared D
Jared D, ASE Certified Technician
Category: Nissan
Satisfied Customers: 1355
Experience:  Shop Supervisor at County Fleet
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AC stops blowing cold after 20 mins and has freon. Mechanic

Customer Question

AC stops blowing cold after 20 mins and has freon. Mechanic says it's the expansion valve but I'm not sure.
JA: How is the air flow? Have you checked the hoses?
Customer: Air flow slows afterwards also. air comes out cool but not cold,
JA: Tell me a bit more about what's going on so he can help you best.
Customer: shop says pressure is wrong on hoses also
JA: Are you hoping to fix this yourself?
Customer: No, I can throw 600 dollar fixes at it not knowing if this is really the issue
JA: OK! The Nissan Mechanic will help you with the diagnostics so you are sure to get this fixed right. Is there anything else the Nissan Mechanic should be aware of about your Nissan?
Customer: condenser is good
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the Nissan Mechanic about your situation and then connect you two.
Customer: no leakes in system either
Submitted: 6 months ago.
Category: Nissan
Expert:  Jared D replied 6 months ago.

Hi,

What year and model is your nissan?

Customer: replied 6 months ago.
2006
Expert:  Jared D replied 6 months ago.

Do you know the model? Pathfinder, altima, sentra, tundra...?

Customer: replied 6 months ago.
2006 Xterra off road
Expert:  Jared D replied 6 months ago.

The xterra has been known to have expansion valve problems. What normally happens is they get stuck in one position. The AC then blows cold constantly until the evaporator freezes up and then air can no longer flow through it. This explains why it not only stops blowing cold, but it also stops blowing very hard. If you had mentioned that it just gets warm then I would recommend checking compressor function, freon levels, etc, but if the actual flow of air decreases then it's almost certain that the evaporator is freezing. The only thing to cause that is a bad expansion valve.

Expert:  Jared D replied 6 months ago.

It is a major job since replacement requires removal of the dash.

If you turn the AC to heat for about 5 minutes (when it is no longer blowing cold) and then back to AC will it blow cold again for a few minutes?

Expert:  Jared D replied 6 months ago.

Please let me know if you need additional information.

Customer: replied 6 months ago.
THE EXPANSION VALVE WAS CHANGED AND IT STILL DOES THE SAME THING. After 20 mins air is not longer cold and restricted. If I turn off the ac for about 5/10 minutes ac will work again for a while. I can't keep throwing 600 dollar fixes at this. Any advice?
Expert:  Jared D replied 6 months ago.

Has anyone taken a look at the AC air intake sensor circuit? If the air intake sensor is faulty it could be telling the AC control unit that the air coming into the evaporator and the evaporator is too hot and then it keeps the AC compressor on for longer than it should causing the evaporator to freeze. It's not terribly common to go bad, but it's all that is left that could be malfunctioning and cause a system freeze up like you are describing.

Expert:  Jared D replied 6 months ago.

Here is a description of the sensor from nissan.

Customer: replied 6 months ago.
How much will that usually cost to check and possibly repalce? What about the Thermistor?
Expert:  Jared D replied 6 months ago.

We might be talking about the same part as I can't find a separate listing for the thermistor and the intake sensor is technically a thermistor. It lists as .3 hours or labor, so about $45 in labor, the part doesn't list a price in my catalog so it is likely only available from the dealer.

Customer: replied 6 months ago.
Where is this located?
Expert:  Jared D replied 6 months ago.

Right behind the glove box.

Customer: replied 6 months ago.
Do I have to have my dash taken off again?
Expert:  Jared D replied 6 months ago.

No, just the trim panel by the glove box. This is much more simple.

Customer: replied 6 months ago.
Thank you. I will let you know how this goes.
Expert:  Jared D replied 6 months ago.

I would have imagined that the mechanic would have checked that part first. That's why I asked if the AC will work again after turning to heat for about 5 minutes back on the 25th. If I had known that it would then I would have suggested checking this sensor.

Customer: replied 6 months ago.
No the guys did not check it. They just went by pressure in the lines. I did not take this to Nissan, they did not have openings for some time. I guess I'm learning a lesson. I will be very upset if this was the issue. They assured me it was the expansion valve, said it was stuck open. I have the off part but not sure how to see if they are coorect. Idiots had my whole dash off. You would think they would.....
Expert:  Jared D replied 6 months ago.

I have to say that I was leaning toward stuck expansion valve as well, but only on the assumption that the ambient temp reading had been checked by the shop. They should have pulled it up on a scan tool to see if the temp reading was stuck.

Expert:  Jared D replied 6 months ago.

Please don't forget to rate.

Let me know if you need additional information.