Just started using the A/C in the last few days and noticed an audible "hissing" as the A/C cycles - lasts a few seconds then subsides... last a few seconds then subsides...

It seems to be cooling OK, but the noise is annoying in an otherwise quiet vehicle.

Before I take it in, I wanted to see if anyone else has expereienced this or has any idea what may cause the noise.

Thanks. 05FKR

 

Does it change frequency any if the engine is hot or cold?

 

Quentin,

No, it does not seem to be temperature related. It does change frequency if idling versus driving. The "hissing" lasts longer while at stop lights, etc.

 

Hm, I don't really notice any hissing out of mine, maybe briefly when the compressor engages, but I really have to listen for it. Might be a bit low on juice, sometimes A/C will do strange things when it's undercharged.

 

That was my thought - the truck has less than 2000 miles on it. I'll stop by the dealer and ask them to take a look.

Thanks, Quentin.

 

2005-Ford-KR,

I have an '05 Supercab Lariat that does the same thing. I have taken it to the dealer and they were not sure anything could be done to it. Refrigerant levels were fine, no leaks, compressor is fine...

Let me know what you find out on yours. I know how annoying that hiss can be. If there is anything that can be done I will try it.

 

For what it's worth, a co-worker had a Navigator that made weird hissing/whistling sounds from the rear A/C unit driving down the road. Come to find out, Ford has a service message floating around that says the system is slightly undercharged from the factory. Something for your friendly neighborhood stealerships to consider.

 

Nateag - will do. If time permits, I plan on stopping by the dealer tomorrow. I'll ask about the low charge as Quentin suggests.

Thanks guys.

 

2005-Ford-KR,

Just seeing if you have had a chance to have the AC looked at. Any info you have would be greatly appreciated.

 

I stopped by the dealership on Saturday, but the place was a zoo. I talked with the service manager briefly and, based on what I told him, he thought it could be fixed. His thought was the unit is undercharged. I am scheduled to go back on Thursday afternoon so they can work on it.

I’ll keep you posted. If you find anything out, please share too.

 

OK, stopped by the local dealer to have the problem checked. It's only 62 degrees here today, so the A/C did not cycle enough to generate the noise.

On the way home I heard it a couple of times which leads me to believe it's worse when the RPM's are up.

Nateag, I'll go back when the weather warms up a bit. The service manager said he'd look at it with no appointment necessary.

I'll update as I get answers.

 

That Noise Is The System Pressure Equalizing When The Comprssor Cycles On And Off . Normal Operation
There Is A High And Low Side On A A/c System . Rangeing From 35-250psi

 

JCC,

Thanks for the reply. I think the sound I am hearing is more than the normal cycling - it is audible as I am driving with the radio on. Almost sounds like the rattle on a rattle snake

I've determined it is louder while driving versus parked and increases in volume as the weather gets warmer (A/C cycling more often?)

I'll post what I find (if anything) after I get back to the service manager.

Thanks again.

 

I couldn't have explained the sound better myself. It sounds exactly like a rattlesnake. The only advice I have received to correct it is to put some kind of sound masking product in there (dynamat).

2005-Ford-KR, let me know if you find out anything else. The snake is getting pretty creepy as the weather is getting warmer.

On a side note, have you heard any other trucks make this noise (F-150 or not)?

 

If I figure this thing out, I'll let you know. It is definitely worse with warmer weather. ARGH!