Looking for ideas where to start. Inside the cab only when the AC compressor is on (AC or defrost during winter) there is a pulsing hissing sound coming from the passenger side of the dash. Any ideas?

 

Connection leak...or possible heater core issue?

 

Im going to try and crawl under the dash this weekend in the 9 degree weather and see if I can better pinpoint where exactly the sound is coming from. I read somewhere just being low on coolant could possibly make this sound. The pulsing appears to be the AC cycling on and off but not sure what is causing the hiss sound.

 

To me...a hiss would indicate something pressurized...that's why I was thinking possible connection leak. Have the level checked and smoke it?

 

Can u get a sound clip or video.. could be ac compressure it self, or sometimes even a belt..

 

I can try later this evening on my way home from work.

 

 

Crappy phone video probably won't help.