I typically do not post comments to "expert" forums such as this as I am admittedly not real proficient in terms of my car knowledge. But with that said, I felt compelled to share my experience here as I know there are probably many others like me who would have gotten fleeced by a dealership to diagnose and repair what is, evidently, a not uncommon, yet very fixable and affordable solution.
Although I'm in Texas, my first sign of an issue (in late 2011) actually involved my heater as it would not blow hot air (or any air for that matter) until the engine was warm (anywhere from 10-20 minutes). Well, because it's Texas, this was more of an inconvenience than a full-on emergency, however it signified the beginning of my many months of fighting through what was clearly not as dire a situation as what many non-auto experts probably fear.
Throughout these many months, I came to realize that the issue would not just go away and as a result, it became increasing more intolerable as the summer heat arrived. While now affecting the a/c, the diagnosis was the same - the a/c would not kick on until several minutes into my trip (when the engine was warm). Thankfully, the hotter it was outside, the quicker it came on. And I should note that the heater and a/c worked perfectly once it actually began to work.
While my frustration really began to mount, I started to resign myself to the fact that the only solution would be to take it to a dealership to try and repair. What gave me great pause, however, was the relative ignorance I got from each dealership. I explained the problem to several different service technicians and was given no assurance by any that my issue would be remedied for anything less than hundreds of dollars. It was the same old line..."bring it in and we'll take a look at it"...the kiss of death for someone on a budget, who knows nothing about cars.
With my back against the wall (and two months of 100+ degree temperatures looming), I came across this forum. I read and reread each post in this thread a dozen times before I finally decided to take the matter into my own hands. While I never understood the technical aspect of the repair as it related to the problem, I felt like I needed to at least try to do it myself as each testimony seems to corroborate the issue I was having. And lo and behold, it worked...this car idiot fixed it.
Anyway, while the previous posts do a great job of explaining how to perform the repair, I wanted to give a step by step instruction for those, like me, who are intimidated by simply raising the hood. The mere fact that I was able to diagnose (thanks to this site) and carry out the repair (thanks to this site) is proof positive that anyone can do this...and not somehow make the problem worse. Here it goes:
1) On the driver's side, remove the fuse box cover below the trunk release and above the hood release.
2) Inside the area of the fuse box, unscrew (with a phillips head) the knee board that runs across the entire driver's side (under the steering wheel). Note: even though this is a rather large panel, there is but one screw that keeps it in place.
3) Disconnect the knee board that you just unscrewed. This panel sort of unsnaps and will hang under the steering wheel. There is a small side panel that will unsnap as well.
4) With pliers (or a wrench), unscrew the three screws that hold the fuse panel in place...the relay that you are trying to get to is on the backside of the fuse panel. In my 2007 Altima, there are two screws right next to each other and a third up and to the right. Once you have unscrewed the fuse panel, it will give you some mobility, but the backside of the panel (where the relay lies) is still pretty hidden. The relay itself (which hopefully you have already purchased) looks like a little ac adapter plug (for lack of a better description). I ordered mine from a Napa Auto Parts by telling them I need a blower motor relay, part #2523079942. It was $26.99 and delivered to my local store on the same day I ordered it. They will probably tell you that it is a non-refundable part, so they'll ask you if you are sure it's what you need. At this point, I became a tad nervous, but persisted as thirty bucks seemed like far cry from the hundreds I'd perhaps be facing by settling on the dealership. Anyway, if you've encountered the same issues as detailed previously in this thread, this purchase is worth the try.
5) Once you have relay in hand, you should be able to see something similar on the backside of the fuse panel. With flashlight in one hand, you should be able to shimmy out the (bad) relay on the far left of the backside of the fuse panel. It will "unplug" from the location closest to the driver's side door. Note: as you unplug it, take note of the position of the prongs upon its release. This will aid you when you "plug in" your replacement.
6) Once you've removed the old and replaced the new, I recommend starting the car to see if you've been successful. It was at this point that I began to sing to the heavens for introducing me to this forum.
7) Hopefully, you are experiencing the same relief as I at this point and simply now need to screw back in the four screws that got you here.
For you car/Nissan aficionados, I apologize for this "dumbed down", lengthy post. But that said, I'd love to know that perhaps just one other person (much like me) was able to gain some insight without throwing hundreds of dollars at the problem.
