what is this thing?

[ned2683]

well i traced my boosed wires from the alda to the intake manifold and along the line it comes into a ... not sure what to call it. it is yeallow plastic with a knob on top of it.. assuming it is between the boost line what could it be.. 79 300sd. thxs for any help

[sixto]

It's a switchover valve (possibly another name?). Under certain conditions, it cuts the boost signal to the ALDA to protect the engine.

Sixto
91 300SE
81 300SD

[ned2683]

so it is not adjustable right? cause i think i turned it a couple times already. if so what are the adjustments? thxs for the reply

[sixto]

You can adjust the ALDA, not the switchover valve. ALDA adjustment is a tricky thing since it's preset and sealed at assembly and you can damage it beyond repair. You have to break the black plastic cap to get to the asjustment screw. Turn the adjustment screw in small increments while observing exhaust smoke and things like that. Search the archives for threads such as the one below for more information.

Question about ALDA adjustment (picture attached)

Sixto
91 300SE
81 300SD