Re: Inline filters to protect AC programmer

[e6941tb@gnn.com]

Southerlin, Russ S wrote:
> 
> If the engine vacuum is "sucking" (I think I hear that sucking sound)
> on the AC programmer to create the vacuum necessary then how does any
> oil or contamination get to the AC programmer? Any debris or oil
> should go toward the engine since it is doing the "sucking".

Engine vacuum creates a negative pressure in the (4) solenoid valves
inside the A/C programmer. When the engine gets shut off, this negative
pressure sucks the oil vapour inside the valves. The valve has a rubber
membrane that does the actual sealing of the vacuum line-to-atmosphere
port. This rubber is not oil resistant. The membrane gets swollen and
seals both ports (vac line and atmospheric) simultaneously => the
solenoid valve stops working.

I once managed to fix it by fabricating a new rubber membrane and
installing it inside the valve - too much trouble. Since then I just get
a used A/C programmer from a bone yard and desolder the valve(s) that
does not have oil in it's port and use it as a donor for a programmer to
be repaired. But you better install that in line filter if you don't
want to repair the A/C programmer on a routine basis.

Igor Kessel
'89 200TQ