Here is an update: I replaced the AC relay. No change. Then replaced the Thermal Control Amp. AC seemed to work good for about a month, then back to the old tricks. I'm still not sure if the AC was just on a long run of coming on every time regardless of the replaced TCA, or in fact, a bad TCA was causing the problem to begin with, and the new one went bad after a month. Here's another clue: The AC is working, then for no apparent reason, it stops. But I leave it on hoping it will start up again ( I live in AZ) After a while, there is a loud screech from under the hood for about 10-15 seconds, then the AC starts again. Here's one more thing to mention. I know this will sound funny, but I think it is another clue. Now that it is cool, the AC will start every time you turn it on. It's when it is hotter than hell I have the problem. What in the AC system fails when it gets too hot, that won't fail when the outside temp is cooler?
I have two suggestions: 1. If you notice that the A/C only works while the vehicle is in motion, especially at speed (such as on the highway) but not while the vehicle is stopped, then the problem may be that the auxiliary fan designed to blow air over the condenser (looks like a smaller version of the radiator, and usually mounted to the front side of the radiator itself) isn't coming on while the vehicle is stopped. No air flow over the condenser means the refrigerant temperature remains the same through this part of the cycle, which translates to no temperature drop inside the car. 2. If you notice that the A/C functionality, or lack thereof, has no correlation to whether the vehicle is in motion, then the next thing I would look for would be a partially faulty A/C compressor clutch, or a fault in the wiring to the sensor that determines the clutch engagement. Realistically though, if you don't have an A/C manifold gauge set you are going to have a serious problem diagnosing A/C issues, as that is the tool that professional mechanics use to do so. Also note that your vehicle (unless it has been retrofitted to use R134a) uses R12, which is extremely bad for the environment should it escape. Bearing these facts in mind, I suggest that you take your car to a qualified local mechanic that specializes in air conditioning issues.
I'd put my money on the A/C compresser clutch or the control circuit thereof, only other thing that I can think of would be a low refrigerant level (or air in the lines?) Have you checked the refrigerant level?
Thank you for replying Doran. When this started a couple of years back, I took it to a "recomended" mechanic. When I went to pick the car up, he said no leaks. It took less than 1/8 of a regular size can of freon. And yes, I am aware of the problems with R-12. In fact, part of the over $400 to fix AC was to retrofit to R134a. Part of the problem I had at the time was that he "thought" the problem was a control switch, or something under the dash. The weather was starting to cool down at that point, so I started to pursue information on my own. It doesn't matter if the car is moving or not, when the AC stops, it stops. On the other hand, when it is working, it blows very cold . I'm not sure if he used an AC manifold gauge or not. Here's one other thing that may or may not have anything to do with anything. The day that I started having AC problems for the first time was the same day a fuel pump rely went bad. Could there be any connection between those two things? Would a faulty AC compressor clutch make a squealing noise while going bad? Thanks again.
To the best of my knowledge, you could get belt squeal from a bad A/C clutch, yes. Another possibility is an A/C compressor with a bad bearing, of the sort that doesn't like to start moving, but once in motion seems to be ok. Personally, I'd replace the A/C compressor and clutch as one unit. If you've had the system converted over to R134a, you can pick up an A/C manifold gauge set relatively inexpensively from Harbor Freight Tools (around $50 or so...if they're not in your are, check out http://www.harborfreight.com). As I had mentioned previously, such a tool is invaluable when it comes to troubleshooting A/C issues.
related question. anyone know how to remove those 3 pins/rivets from the clutch plate so you can thread the clutch removal tool in. i tried vice grips, screwdriver, etc. nada
there is no power in the AC switches, athey sometimes come and goes off. I dont seem to know the problem.
Looking for a Used Sentra in your area?
CarGurus has 52,952 nationwide Sentra listings starting at $1,799.
Search Nissan Sentra Questions
Nissan Sentra Experts