Sad Or Supplementary Air Device Testing

[welshpug 1,621]

Have seen quite a few threads asking about these and blaming them for allsorts of faults, I guess not many actually have Haynes manuals these days?

 

A very much maligned and over thought device, its a very simple rotary disc operated by a bimetallic spring, which has an electric heating element next to it, as well as being bolted to the side of the thermostat housing, there really isn't a lot to go wrong and they don't move fast and wear out like a more modern ICV/Idle control valve

The Jetronic system is very much clockwork and has no idle control built in, the SAD purely reduces the amount of supplementary air that bypasses the Throttle butterfly the longer the ignition is on and the warmer the engine gets.

 

So here's an extract from the Haynes manual.

 

 

 

as you can see, very simple!

 

 

here's the schematic -

 

 

As you can see, its earthed through the starter solenoid, the very same wire that causes that oh so common 'click' and no chooch from the starter motor when you turn the key, so if that's causing voltage drop issues to the starter, it will also cause a high resistance on the earth side for the SAD so it'll take longer to close.

Edited October 25, 2017 by welshpug

[Telf 222 2 Cars]

Good work Mei.