Noise when AC is on at 3500rpm-4500rpm?

haywoodphotomaccom · 06-30-2015, 06:58 PM

There is an intermitent noise that happens when the engine rpm gets above 3500rpm when on the throttle or coasting and it is only present when the AC is on. It's a low drone type of noise that goes away as soon as I turn off the ac and will return as soon as it's switched on but needs to be in that rpm range.

It does it when it's hot or cold.....

There seems to be a slight drop in power when this noise is present. It eventually goes away each time even when in the rpm range.

It does not seem to be the auxiliary fan as I hear it come on occasionally too.

Any ideas?

larrie · 06-30-2015, 07:23 PM

AC compressor bering?

JWA · 07-01-2015, 03:26 AM

Because this noise is centered around the A/C compressor as Larrie suggests it could be those bearings---something within the compressor itself is beginning to fail it would seem

This could be the clutch assembly which is replaceable separately. I'd check the serpentine belt tensioner too for proper operation but its doubtful that plays into your noise.

haywoodphotomaccom · 07-01-2015, 06:43 AM

Great info, taking it in tomorrow for an inspection. I had a new AC system
put in last year which needed a repair almost right away. Wonder if they did not catch everything.....

boywonder · 07-01-2015, 07:39 AM

As already mentioned...perhaps serpentine belt resonance? Can you duplicate the noise parked with the hood up? If the belt is flapping you should see it....

carringb · 07-01-2015, 09:43 AM

Can you stick a go-pro under the hood? A weak tensioner can cause the belt to flutter at higher RPMs.

Also, a fluttering expansion valve can make strange noises. I think Ford even had a TSB for that.

haywoodphotomaccom · 07-01-2015, 09:46 AM

All good info, going to see if I can bring it in this am for a check up......report to follow....

haywoodphotomaccom · 07-22-2015, 10:22 PM

Finally got a chance to take the van in for an inspection today. The tech seems to think there may be to much freon (pressure) in the system causing problems with the compressor. He is not positive yet as I was not able to leave it today but that is his current thought.

One thing I was not excited about was he stated he may need to let some out which would reduce the cooling capacity. It barely cools as it is.

Dropping it off next week for the day. I'll update when I get it back.....

carringb · 07-22-2015, 10:56 PM

Quote:

Originally Posted by haywoodphotomaccom

One thing I was not excited about was he stated he may need to let some out which would reduce the cooling capacity. It barely cools as it is.

Too much freon reduces total efficiency as well (too much volume reduces the overall expansion ratio in the system), so it might cool better after bleeding some off.

haywoodphotomaccom · 07-22-2015, 10:57 PM

Good to know. Can there be damage to the overall system with to much in there?