Jerky movement with the box between 1500-2000 RPM

Hello,

My 1Z TDI engine vibrates when the auxiliary heating system is active, specifically between 1500 and 2000 RPM. I bought the auxiliary heating system used and without an instruction manual. Which potentiometer should I adjust, and in which direction, to improve the situation?

Best regards,

Hi.

AFAIK, there are several generations of speakers available from Authal.

Could you please post a photo here? Maybe someone will recognize the box.

Thank you for the quick response!

It's difficult to take a picture right now because the unit is installed, but it was manufactured in either 1994 or 1995. It consists of two metal housing parts, and on each side, there are plastic covers that slide over them (it's all quite unclear). It's kind of like a large matchbox, but the outer casing is in two pieces.