[pierze]

I've got an 04 SE with Big Town and Off Road packages that I bought new in Feb 04. Over the past two years or so I've noticed the A/C doesn't get as cold and it takes longer to cool off than it used to (both of which probably just mean "it isn't removing heat as fast and as well as it used to"). I've also noticed a strange "hissing" sound, almost like a valve opening and closing, that happens every 30 seconds or minute when the system is actively cooling. It is easier to hear this sound when the blower is set to 1 or 2, since 3 or 4 get a bit loud and drown out the sound.

I just had my Titan serviced today for the PB081 recall ("ac condenser fan overheating issues"). I'm not sure what they actually did or didn't do, but it did not change my symptoms at all (and yes, I showed them the problem beforehand). When I got my truck back they said the hissing is a symptom of being low on Freon and that my system needs a full flush and refill for $140.

I'm wondering if any of this sounds familiar (the hissing, the lesser cooling ability)? I haven't done the flush yet as I wasn't convinced the dealer was basing that on anything other than my milage and their ability to try to squeeze dollars out of me (~74000 miles). I have my own R134a recharge kit and checked the pressure on the low-side of the system (duh), which varied between about 35-38PSI at about 75-80 degrees today, so I'm pretty sure I'm not low on Freon.

I'll shoot a video of the sound tomorrow and post it here.

 

[Walrus]

The hissing noise is the expansion valve opening and closing.
Got cabin filters?
If they are crusty, your aircon will suffer.

 

[pierze]

I haven't checked the cabin air filter, which was last replaced at 49K miles and it was in pristine condition. I haven't done any real dirty driving since, so I haven a feeling this one is still fine, but worth checking anyway.

Is it normal for the expansion valve to open and close this often?

 

[pierze]

First I inspected my cabin microfilter. It is somewhat dirty, but looks fine to me - certainly not clogged. However, in order to scientifically eliminate it as my problem, I simply removed the filters (plural because there's actually two pieces to the "filter") and closed the system back up, thus removing all restrictions in the flow. To my lay observation this made no difference whatsoever.

I've attached an image of the filters.

Next I ran the "official" A/C testing method following service manual, page MTC-83, "Air Conditioning -> Trouble Diagnostics -> Performance Chart -> Test Conditions" and took both a video and some pictures, as promised. I uploaded the video to YouTube. The interesting part starts at about 1:20, meaning you can hear the "hissing cycle" from about 1:22 to about 1:29, then a few more times in a row over the next 60 seconds or so (meaning my original guess of "every 30 seconds" was a really inaccurate approximation, sorry!).

Ambient temperature readout at ~85F, although my car is black and that thermometer seems to read a bit high sometimes. My Oregon Scientific unit claims it is 72F outside and I believe that more. It is a relatively cool and beautiful Southern California late morning, not hot or humid at all.

 

[08crewcab]

For them to tell you you need a flush and you're low on freon is non sense. Freon doesn't go bad, so a "refill" would just be a waste of $! bc if you are really low on freon you have a leak... Good luck brotherrr

 

[beason]

yea you got a leak somewhere. the hissing is a sign of low freon. you can just refill it, and see how long it lasts, or you can try to find the leak. refil shouldnt be to expensive, and you can even get the stuff at walmart, although its not exactly a pro job.

you should be able to look at the lines and find the leak. freon has oil in it. look for the wet spot.

 

[08crewcab]

buy the refill kit with dye in it.....if theres a leak you will find it!