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Compressor frequently cycling when driving - hissing when compressor kicks on

everfrost on Fri June 19, 2015 8:52 AM User is offline

Year: 2011
Make: Nissan
Model: Versa
Engine Size: 1.6L
Refrigerant Type: R134a
Ambient Temp: Variable

Hey folks. First time posting here, hoping to find an answer to this issue. I've searched through past posts and online, but can't find anything specific to my issue with the Versa. If I've missed a post somewhere, I apologize in advance, and would be grateful for a link to that thread.

So, starting at the beginning. I was having issues with the AC in my Versa and had dye leaking from my evaporator drain, so long story short, I had my evaporator core and expansion valve replaced. Had the system vacuumed and charged per manufacturer spec (0.99lb according to sticker on hood) at local auto repair shop. Car is cooling well with no leaks, but...

Since having this repair it seems like the compressor is cycling too often while driving. When driving, it seems like the compressor will cycle on for around 6 seconds, then turn off for around 10-15 seconds, then repeat indefinitely. Every time the compressor engages I hear this hiss from under the dash (in the area of the evaporator core). This seems to be the case regardless of ambient temperature and humidity conditions. I feel a very significant engine drag when the compressor engages, and subsequent return to power when it disengages. I understand some engine drag to be normal when the compressor engages, but it happening every 20 seconds isn't something that I have noticed in the years before this repair. I can recreate this happening at home by simply having some keep the engine at about 3200 RPMs (normal RPM while interstate driving for this vehicle).

So I took it back to the mechanic and related my issues...The reassessed the lines and found no leaks, so they evacuated, vacuumed, and recharged the system per spec. No change in any of the items I have mentioned though...

So I took it back again, they did the same, with no change...

So with refrigerant at the proper level per spec, new evaporator core, and new expansion valve...where should I be looking? I'm going to hook up a set of gauges this evening or tomorrow and and try and see the pressure changes in between these cycles and I'll post them here once I do.

Is it possible the pressure switch (transducer) is bad?

everfrost on Mon June 22, 2015 7:35 AM User is offline

everfrost on Mon June 22, 2015 7:40 AM User is offline

Pressure readings....

At idle, high pressure stays around 200-225 psi, low pressure stays around 30 psi with compressor engaged and cycling what I would call normally (fairly lengthy amount of time between cycles).

With any RPMs above idle on the engine, the high pressure remains 200-225 psi, but as soon as the compressor kicks in the low pressure drops immediately to 5 psi or lower for around 8 seconds then the compressor cuts off and pressures return to 220/30 for about 8 seconds then compressor kicks back in and drops low side to 5 psi for 8 seconds...repeats indefinitely as long as engine is not idling.

Any ideas????

Metal Man on Mon June 22, 2015 8:53 PM User is offline

I'm no pro but I would suspect the TXV. Did you use a OEM TXV or buy on of the (cheaper)after market TXV's.

I once bought a cheap after market TXV for a Honda and had similar results, wound up cleaning and using the original TXV to fix my problem.

everfrost on Thu July 02, 2015 3:02 PM User is offline

Thanks for the reply. I might give this a try. They used the generic TXV from Autozone for the repair. I've had them replace that again, no change. They've also flushed the system and replaced the drier. No change either.

GM Tech on Thu July 02, 2015 4:15 PM User is offline

So why did they change the TXV? when the evap core was leaking--the original TXV is always best- what you are hearing is TXV hiss from the aftermarket TXV installed- By changing the TXV, your mechanic has caused numerous undesirable side effects-- put the OEM one back in.

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

everfrost on Mon July 06, 2015 6:39 PM User is offline

The original wasn't working properly so they replaced it first. I don't have the original and doubt they still have it around either. The best I can do is purchase a new OEM one from Nissan.

What about the pressure drop when the engine has a load on it versus just idling? Is that normal for an instantaneous low pressure drop from 30ish to 5 to 10 psi when there is a load on the engine? If I just let it idle with AC compressor running, there is no sudden drop like that...it never falls below 20. Is that yet another sign of a funky expansion valve?

Thanks again!

Chad

mk378 on Tue July 07, 2015 8:33 AM User is offline

Higher engine rpm, compressor works better, low side drops, evaporator gets cold, temperature sensor cycles compressor off. In other words, normal operation. You should be testing with the interior fan on high and the doors open-- so it does not get cold inside the car and the A/C is forced to work at maximum heat load.

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