Common Problem?

[Zero Six LE]

Originally Posted by PoolRunner

My brand new '08 does this, so does our '08 Mercedes C300 and nearly every vehicle I've owned over the last 5-7 years, I go through a lot of vehicles. I don't think it's anything to get excited about. I actually think it does this to help conserve fuel and such.... some Ford vehicles actually have a device that kills the A/C compressor after a certain range in the RPM to help aid acceleration. If that were the case with my Nissan it would never be cool inside the cab.

-Ryan

All modern vehicles have a compressor cut out under WOT.

[nissanmastatek]

OK first of all lets have a short lesson on how this system works for those of us who are squabbling over system operation and whether to call it fast cycling or short cycling. The ECM uses a combination of readings from the a/c pressure sensor, in cabin sensor, and thermal control amplifier. All these sensors (like most items on cars) have 5 different names, so shut up and play nice, you know what i am talking about. The ECM uses these readings and controls compressor clutch engagement accordingly. Therefore, an ecm re-flash would remedy this situation. Also, normal cycling is used for a variety of reasons. Fuel economy yes, but when fast cycling this will be compromised as loading and unloading the engine uses more fuel. Mostly it is used to control cabin temperature and prevent evaporator freeze up, as well as prevent wear etc. finally, this doesnt seem to be a problem off idle, and yes it should happen more often with the fan on 1 setting as the lower the fan speed, the cooler the evaportor will be.

[jim willcock]

hi maineruner im new to this forum as I live in the uk but I can not stop myself from commenting This guy is trying to help he has a problem like alot of you dont be negative and dont be picky about his discription/title of the problem. This is a forum where we all pull together and unite to sort problems and fight in numbers dont want to get heavy but as I said the guys put himself forward to help. Hope he gets it sorted if you want to log on to the uk sites may give you more ammo to fight nissan with good luck

[shaggyusm]

Originally Posted by nissanmastatek

OK first of all lets have a short lesson on how this system works for those of us who are squabbling over system operation and whether to call it fast cycling or short cycling. The ECM uses a combination of readings from the a/c pressure sensor, in cabin sensor, and thermal control amplifier. All these sensors (like most items on cars) have 5 different names, so shut up and play nice, you know what i am talking about. The ECM uses these readings and controls compressor clutch engagement accordingly. Therefore, an ecm re-flash would remedy this situation. Also, normal cycling is used for a variety of reasons. Fuel economy yes, but when fast cycling this will be compromised as loading and unloading the engine uses more fuel. Mostly it is used to control cabin temperature and prevent evaporator freeze up, as well as prevent wear etc. finally, this doesnt seem to be a problem off idle, and yes it should happen more often with the fan on 1 setting as the lower the fan speed, the cooler the evaportor will be.

That definitely makes sense. As with having the fan on "1", I also think that while driving, the compressor doesn't kick on as much because of the air moving over all the A/C parts under the hood that would be more sensitive to freezing up at a rest. There isn't as much under-hood-air-circulation while sitting, at say, a drive-thru. I know the compressor doesn't cycle like that while driving because you'd be able to feel it. I can tell when the compressor clutch engages at lower speeds and it's definitely not as often as it does sitting at a drive-thru or in a driveway.
Thanks!

[Pops]

Originally Posted by nissanmastatek

.... That is about all I will say, i will not get into detail b/c nissan does monitor these forums. ......

/RantON: If they monitor these forums then they should fix the freakin' problems instead of worrying about what you have to say about their stupidity. There's a known issue with the crappy radiator caps leaking on the VK56 posted all over the Titan forums that Nissan won't address, I'm on my 3rd one now. MasterTech or not, you're still a customer and you deserve to be treated as a good customer. /RantOFF

Anyway, I'm sending you a PM for someone who might be able to help you and if not he's still a great friend to have and he's an awesome guy.

[Jumbo]

Ok cool. I am all for helping in any way that I can. Not to be negative, but I really don't think that anything will come of this since Nissan doesn't even seem to be interested in helping to fix some of the here-and-now problems that people are having. But, it never hurts to try!

Also, thanks to "nissanmastatek" for bringing this to our attention. In the mean time, I think I will keep my fan on at least the "2" setting unless I am on the highway.

[nissanmastatek]

thanks for your help guys. Like I said before, it takes an act of congress to get nissan to lift a finger. And, as you said pops, i am no longer an employee, but like all of us i paid 20k for this thing and a simple engineering issue should be taken care of. Oh and dont get me started on the Armada/Titan vehicles, that list is a mile long. I will contact Nissan shortly and let you all know what happens. I expect the usual phone tag but we will hope for better. thanks again