'04 frontier 6cyl, 90k miles. My AC recently started cooling poorly, although still slightly cold, especially at higher rpms. At the same time, I noticed a buzzing noise that changes pitch with rpms and only occurs with ac on. I can hear it loudest from the glove box area, and can’t really hear it under the hood. The compressor clutch works fine. With the car off, I can spin the compressor and it feels fine, no noise. With ac on, the low pressure tube gets cold. Any ideas? I hope it’s not a bad compressor.
The only buzzing I’ve ever heard coupled with poor AC cooling turned out to be a bad compressor clutch. Use a piece of rubber hose to listen to the clutch or just watch it’s action with the AC on.
Maybe you have leaves and junk stuck in the cabin air filter which is behind the glove box. Look at https://youtube.com/watch?v=roCuW9wqZv4
Try and look inside the housing when you have the filter out and see if there are big things stuck in there.
The buzzing noise might be coming from the expansion valve located at the evaporator.
https://www.rockauto.com/catalog/moreinfo.php?pk=3906144&cc=1428410&jnid=456&jpid=0
The evaporator is located in the HVAC plenum behind the glove box.
This can easily be checked by attaching a set of manifold gauges to the system and observing the low/high side pressures.
Tester
Ok, I did some more testing. With an AC manifold gauge I determined that the Low side is to high (55-60) and the high side is low normal to slightly low (155-160). I sprayed the condenser with water and the pressure readings became more abnormal, low - 60psi, high - 125psi. Any ideas now? I am still worried it might be the compressor because of the readings, but I’d think they would be closer together if it was a failure.
Those low/high side pressures are way off.
I’'ll give you an example of what the pressures should read.
With an ambient of 90 degrees, with engine running at 2,000 RPM’s, and with a large fan blowing at the condenser, the low side pressure should read between 35-40 PSI, and the high side pressure should read between 280-300 PSI.
If the pressures don’t reach these values under these conditions, and there’s a buzzing noise from the glove box area, and the air isn’t getting cold enough, I’d say there’s a problem with the expansion valve and not the compressor.
Tester
Thank you for the response. I’m assuming you think the EV is stuck open? I hope that is the case. I just dropped it off at the dealer for service in the morning, as I have no way of reclaiming the refrigerant any ways. I’m interested in thier conclusions as well. I have decided that I wish AC systems were more servicible by the home mechanic!
They say it’s the compressor. They said they thought it was the expansion valve but tested it and it’s not the problem. They said the nissan tech who tested it has 30 years experience. What do you think?
Ok so compressor replaced, I have cold air again but the damn dealer sent me home with low refrigerant now and the new compressor seems to be short cycling. I think I’m going to have a stroke over this.
They either did not fully charge it or there’s a leak. Any A/C repair job should automatically mean checking for leaks. Take it back and make them stand behind it.
What I’ve always done with A/C repair is that once the job is finished I pull a vacuum on the system and then allow it to sit for half an hour. If there are no leaks the vacuum reading on the gauge should not drop. Any leak at all and the gauge will drop off. This saves having to use refrigerant to leak check.
Once charged I then go over it with an electronic sniffer.