nesh216

When you have the air set to recirculate, the A/C automatically comes on. My question is that if you have the temp control all the way to 90 (heat) and have it to recirculate so the A/C is on, is this inefficient?
In other words, is the heater better when recirculating (A/C on) or pulling in outside air? I have tried both ways and can't really tell which is hotter.
What do you guys do?

davidv

iTrader: (2)

The heater works better if the air conditioning is OFF. The primary reason to have the air conditioning ON is to dehumidify the cabin: eliminate fogging windows.

ZZ33bOI

yeah tats on ALL nissan cars...i dont kno why my uncles murano does the same thing..its one of the poor designs made by nissan...but tats just my opinion

SeanG

The heater will work exactly the same A/C on or A/C off. The A/C light is on, but the compressor only runs for a couple of minutes then shuts off. The Evaporator is all that remains on, to dehumidify the cabin. Every car that has an Auto Climate Control does this by default, not just Nissan vehicles.

Those without Auto Climate Control still activate the Evaporator when the controls are turned to defrost. Because it is a push button the light in most cases just does not light up to tell you the A/C Evaporator is on (Sentra, Eclipse,Neon ect.)

This is not a bad thing either. You dramatically decrease the life of your A/C components if you do not run it periodically during the winter months. The A/C Compressor needs to be ran several times a week to keep the bearings properly lubricated. Most manufactures even state in their manuals that the A/C MUST be ran for 5-10 minutes a certain numbers of days a week during the winter months, or it will void the warranty on the A/C Compressor.

As far as Recirculate or outside air. It is better to put it in recirculate for a bit, which will heat the cabin up faster. But, is recommended to put it back to outside air once you feel the temperature is at a comfortable level. I believe some of this is in the manual.

Z MANIA

Good to know, in case we ever have a winter month in California. Sorry about that east coasters.

highside107

iTrader: (1)

Good to know! I had some AC technician tell me the same thing before as well. What do you mean when you say run the Compressor a few times a week during the cold months? I mean.. is the Compressor "on" when we defrost as well? Or is that just the evaporator that's on?

SeanG

If you use your front defroster a couple times a week, you will be fine. The warning is mainly for those who garage their Z's for months on end without running the A/C. Very, very bad on the system. The bearings dry out, then it takes a bit for the lubricant to re-lube the bearings. Over time creating excessive bearing wear, and failure.

The Compressor is what makes the air cold (boggs down motor, eats up all your gas). You can tell when the Compressor is on, by the radiator fans. There are two of them in the Z. One is for the engine coolant, one is for the A/C compressor. In the cold of the morning, with the A/C active, you will briefly hear the Compressor fan on, this means the Compressor is ON. In the heat of the summer, with the A/C on, the compressor fan will always be going. When the engine gets hot then the other one turns on, with both going, now your Z should sound like it is going to take off in flight.

The Evaporator is what removes moisture out of the air before it enters the cabin. If your A/C light is on, then the Evaporator in most cases will always be active.

When the outside air is colder than what the thermostat in the car is set at, the Compressor will come on briefly (first starting up the car) for a couple of minutes (Lubricates), then shuts off. If you leave the A/C in the AUTO position, the Compressor will come on and off every so often, but it will not remain on in cold weather. It knows it is not needed to cool the inside of the car. Plus, if the Compressor was on constantly in the winter it would freeze up the A/C system.



The entire system knows when and what is need to keep the vehicle at the set temp. It is just easier to set in AUTO and leave it there. The Climate Control in the Z will even shut down the compressor in the summer when your doing some spirited driving, when your done beating the crap out of the car, it comes back on. There is no need in the Z to shut the A/C system down when you want more power like in most other cars.

Your gas mileage will not suffer in the winter months by leaving the A/C system on, like in the summer months. I feel like I'm in A/C 101

julian

kind of right but not exactly. the evaporator is never active or inactive, it's the refrigerant that the compressor moves being active.

the compressor doesn't shut off because the interior cabin temps are at the set point, it shuts off in cold weather because the low side pressure has reached the limit and the PCM tells the compressor to shut off. the low pressure switch is to avoid icing the evap core, or if there's not enough r134 in the system.

if a vehicle has automatic climate control, the control head will vary the temperature blend doors in response to the user's set point. it doesn't cycle the a/c compressor to reach interior temperature. the a/c compr only cycles off when the refrigerant pressure is too high, too low, if there's a WOT cutout programmed into the PCM, or if the engine is overheating.

bmxox

iTrader: (1)

exactly, the only part of the system that is on or off at any point is the compressor. otherwise its like saying turning your radiator on to cool your coolant.