Posted: Jun 07 2007 at 11:30am | IP Logged

I'm having an odd AC issue w/ my Nissan Frontier King Cab, 2001 (manual Trans.).  I'm in Southern AZ, and it gets H-O-T here.

Last September I noticed an issue w/ my AC.  When my Truck was left in the sun or in the heat, the AC would blow hot for a little while, then cold for a little while, then hot for a little while, then cold for a little while, and so on.  It does not correlate to accelleration or anything else.  Sometimes I'm accelerating and it blows cold, sometimes hot.  Sometimes I'm at a complete stop and it blows cold, sometimes hot.

As winter came in (winter in Southern AZ is warm in the afternoon 55-65 degrees) my AC worked fine, no issues.  As the weather warmed up again for summer this issue resurfaced.  ONLY on hot days or when left out in the sun for a while.  So, in the morning when I get up for work, my AC works great and consistent. Nice and cold.  Eventhough I park in a garage, the afternoon drive home is awful w/ hot and colt, hot and cold.  Subsequently, the cab never gets cool and I'm sweatin' it out in triple digit degree weather.

About a month ago I took it to a local chain mechanic w/ excellent rating from the BBB & has won awards for service and ethics.  I've used them to service my vehicle (never serviced AC before w/ anybody) and I've been happy with em'.  So, I brought it in and explained the problem.  After they had a look see.  They said that the performed their service, flushed the AC system.  They saw no leaks or operation issues (compressor OK, etc.) The freeon or whatever was a pound low, so they filled it and added a dye to it.  The dye was added, so if my problem continued they could easily see if there was a leak.  Well, after a couple of days the problem resurfaced.  So, I brought it back in.  They looked at it for several hours unable to find any issue with the AC.  No leaks, no compressor problems. nothin'.  Finally, they decided that my battery poles had been corroded (and they had) and they said that the AC needed more juice from the battery in hot weather and couldn't get it due to battery pole corrosion.  So, they cleaned off all the corrosion, made sue the battery cells had water and reattached the battery to the truck and said they got it to run cold consistently.  I drove (mid-afternoon) stopped at the grocery store for an hour and came out to the same old situation.

What do I do now?  I'm afraid to take it to the dealership and hear that they will just replace the whole unit for $ 1 billion Zillion dollars.  There has to be an issue somewhere.

I had the transmission and clutch rebuilt in April, but I was having this issue before and after that, so I don't think it can be connected.

Any thoughts?

Posted: Jun 07 2007 at 5:16pm | IP Logged

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Ramses ii;

I don’t use the defroster very much. BUT, what really hacks me off is adding heat to the A/C! We noticed in our 95 Quest, ’95 King Cab and ‘99 Frontier heat was flowing automatically when the A/C was running, how stupid is that?… I’m using extra fuel to cool the vehicle and the system is adding heat to it! Maost the other car brands besides Nissan are doing this. I don’t know the answer to your question but here’s what I do to reduce the problem. I run the A/C wide open (max cold) and manually turn the compressor on and off. I turn the compressor off going up-hill and back on during the down hill run… This seems to conserve power, fuel and seems to stop the heat flow.

It might be that the door to the heater core compartment is not completely closed or Falsely opened by the computer. Most ALL modern cars mix hot air with the cold air when the A/C is on to keep the temperature at an even setting. Several of the Nissans and our Grand Cherokee I’ve had will get a hot spot on the middle of the floor close to the dash if the A/C is not set for maximum cold. Our ‘04 Sentra automatically turns the A/C on when we use the defroster and it won’t turn off until the ignition switch and engine is turned off. We no longer use the defroster, we just turn on the A/C and it will do the summer time defrosting.

Though drying the air with the A/C on is a little more efficient and might be needed at times (like you have seven passengers breathing heavily) it takes extra gasoline to run the A/C. My mechanic friends tell me that (A) all late model cars are set up using the A/C with the defroster and (B) I can cut the wire to the A/C pump clutch and add an off-on switch in that wire.

Well the wife’s ‘04 Sentra has the same defroster problem. The A/C pump will shut off when the blower fan is turned off but will restart if the fan is turned on. The only way to stop the process is to turn the ignition switch off and restart the engine. We have not contacted the dealer about this. It’s kindda like a Micro-Soft XP programmed computer.

Posted: Jun 20 2007 at 1:15pm | IP Logged

dcsmith wrote: My wife's frontier has symptoms similiar to those of the original poster.  Is this forum designed to help people find answers to problems or is it just a forum to vent frustrations.

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dcsmith;

... Sadly we have many "Indians" and too few “Technician Chiefs”.

As a pre-computer ex-line mechanic I can only define the principles of an A/C system. Prior to A/C integrated into the computers.

Posted: Jul 05 2007 at 11:00am | IP Logged

You may want to do some research on a part called a “thermal control amplifier” This is a small electrical part that is located behind the glove box stuck in the evaporator coils.  It tells the computer if the system freezes up.  If this part malfunctions like mine did it will be cooling fine one minute and blowing hot the next. The TCA turns off the compressor so when it stops cooling check that first.  Replacement part at Nissan $45 and if you get in the floor and look behind the glove box you can see the little white three pin connector .