Chevy & GMC Vans

Over the last 2 months a noise has been occuring and more and more regularly. Under harder acceleration and usually when the transmition shifts into 2nd or 3rd a buzzing noise occurs, sounding like a relay or selonoid buzzing. If i let off the gas a bit it will typically stop but is starting to stay longer and longer. The noise sounds like it is coming from behind the dash in the engine compartment. This seams to have similarities to sysmtoms of the encoder motor but it is not while on slick surfaces nor does the awd light ever come on.

It has been hard to test because it only happens while driving, any help here would be greatly appreciated.

Ryan

I dislike the way they route Vacuum Lines behind the dash for heater controls etc. It opens up a Pandora's Box of problems, I think...
I prefer the oldest Astro with push cable heater controls.
Jus my 2 bits...

To add some more detail. When I let off the gas the noise doesn't just fade out or change....it is either on or turns off.

Thanks for your help,

Ryan

Ok more info....i have narrowed this down to being associated with the air conditioning. If i turn the ac off while the noise is going the noise stops. Similarly if i have the ac off the noise never starts. I have thrown spare ac relays in for both that are in the fuze box with no change.

Any thoughts?

Ryan

Hi,
Maybe just AC compressor clutch.

AP

After reading, I'm reminded that my van did this for a period of time. I thought it may have been related to t-case/tccm/encoder too motor and it happened exactly as you described.

It went away at some point and not sure if it was related to the A/C clutch replacement, never really thought of that.

The A/C clutch was making quite a bit of noise on engagement/disengagement and clutch debris (dust) everywhere so I replaced with a Compressor Works 677802 clutch/pulley/bearing/coil kit from Autozone. I could see where potentially if the clutch was worn and air gap too large, it could vibrate, maybe.

If its somehow related to AC maybe check whatever is in your squirrel cage if you have one, I think I recall something in there makes a noise as well when it starts to go, but that is a shot in the dark, I dont even know if we have those on our year.

Hey thanks guys, i haven't had time to look any farther but am thinking you guys are right on with the compressor clutch.

Thanks,

Ryan