Automatic Volume Control: This is called different names by different manufacturers, but the idea is the same. The system automatically adjusts the radio volume up or down, depending on the vehicle's speed.

Can anyone tell me if the ISO connector has speed pulse associated with the vehicles speed to allow for head units to automatically adjusts the radio volume up or down, depending on the vehicle's speed.

I've been told it should be on pin 1 of the ISO connector and be called speed pulse.

 

Automatic Volume Control A useful feature that is found on high end head-units. Some have a microphone that 'listens' to the background noise and some are connected to the car's speedo. This feature prevents the music from becoming inaudible against rising background noise as you speed up.

 

The speed pulse may well be on the ISO connector, but I don't think it is connected on the Subaru wiring loom.

Never heard of such a thing, so can't comment any further.

Here's the pinouts for the Impreza wiring loom which may (or may not) explain things - http://www.ravensblade-impreza.com/m...ing/radio.html

Stefan

 

did a search for speed pulse and found that it is on the one of the ECU connectors pin 83.

 

Hi, most head units do use a microphone that ,as you say ,listens to the road noise and adjust's the volume accordingly. My mate's ahhmm Zafira's head unit has this function and thats a bog standard Vauxhall unit so it's not that uncommon, don't know about the speed pulse bit , but i am certain that most H/U's will use the mic type of system.

 

Golf Gti's have this too, although mine wouldnt work properly

 

I dont think headunit have mics anymore - they are connected to the speed pulse, and as the speed increases, the volume increases. This is common on VW units, where the speed pulse is at the ISO.