I recently purchased a used '99 5.7 Suburban and have noticed that once in a while I will get an intermittent low tone whistle ONLY when the AC is on. This whistling sound will only last for a few seconds and is more prevelent when moving through different low RPMs such as stop & go traffic etc.
I have not been able to duplicate while stationary and cannot pinpoint the origin of the noise. When inside the vehicle it sounds like the noise originates from the right-hand side of the engine compartment (condenser?) vs. the left-hand side (compressor/clutch).
If anyone has heard of something like this before I will appreciate the feedback. My AC works fine, gets nice and cool, however I would like to prevent something from failing if this is a maintenece issue.
Thanks in advance.
G-Man