What's that vacuum-actuated solenoid valve in heater hose??

[fixizin]

... what is it for and when does it ever move? Heat all the way on or off, it stays in the same (apparently OPEN) position, solenoid extended, all the way to rear.

I live in a hot climate, so maybe this is to shutoff flow to heater core so engine warms up faster in cold weather, so that's why I don't see it move...?

Needless to say, no mention of it in Chilton's on CD.

 

[almostclueless]

Should be the shutoff to make the core cooler, like on A/C equipped vehicles.

 

[fixizin]

Should be the shutoff to make the core cooler, like on A/C equipped vehicles.

Nope, A/C on or off, it's still open... in fact, you sometimes need both heat AND A/C, such as for windshield de-fog.

Whatever, it's 2 more joints and 2 more hose clamps when I replace the hoses...

Anyone got the Helms/factory scoop on this gizmo?... just wondering, as I'd like to swap out all the vacuum hoses too... although those small gauge plastic (silicone?) vac hoses STILL look GOOD.

 

[mfp4073]

IIRC, its supposed to shut off when you put on "max ac".

 

[V8 Level II]

IIRC, its supposed to shut off when you put on "max ac".

Yes, it actually shuts off coolant flow to the heater core in 2 positions: MAX A/C and OFF.

 

[fixizin]

D'OH!!... you are correct, it's a MAX A/C flow-stopper... thanks much. I'll do a little more thinkin' and checkin' next time...

Ironically I always use MAX (no outside air, recirc), except lately we've had strange HOT dry winds from the West, so I was using Norm-A/C to air out the mildew in that neglected pathway... so when I checked, it was open...

Never use the OFF position either (i.e. I leave it on VENT when parked, and windows cracked, for convection cooling), but cutting off the heater core then makes sense too.