Sanden makes growling noise at specific rpm

[macster2751]

I have a Classic Auto Air system in my Corvette. The system cools fine but the Sanden SD7H15 compressor makes a growling noise but only between 1500-1700 rpms. It is quiet at all other rpms. It seems to be worse (louder) after operating for 15-20 minutes when everything is heated up. I even avoid turning on the system except when it really hot outiside. I've checked the usual suspects, compressor mount, hoses rubbing and all's good. Pressures are 10-30 low side and 190-225 high side at 80F which according to CAA are within normal range. Vent temps typically 38-45F. Any ideas why it's only noisy at a specific rpm range? If the compressor was bad, wouldn't it be noisy all the time?

Perplexed.....

Mac

[Carguychris85]

My experience with that compressor was not great. It is noisy because of the gears inside of it and it lacked displacement and BTU capacity compared to a GM compressor.

[Tim]

You can try an inline muffler on your suction side. This model is much better (noise) than the SD508 series. Overall, they are good compressors, IMO. Is it a true Sanden or an imported knock-off?

[macster2751]

Thanks for the reply. Where does one get a suction line muffler? Compressor has Sanden label on it but there are no Sanden markings on the compressor. Label says to use SP 15 oil. I think I bought it from Retroair.

Mac