[Hillis33]

The Oil light on my 2004 forester xt has been flashing rapidly when decelerating or at an idle. When I press on the gas it stops lashing but then returns once I let off. I recently changed the oil pressure sending unit on my car after the last one failed, so initially i thought it was a bad connection. But i went back in and made sure the sensor connection was on properly and tight. not sure if maybe I messed up the installation or if maybe the new sensor is picking up a problem that the broken one wasn't.

 

[DragonSubie7]

The oil pressure sender is really just a single pole switch that requires pressure to keep it "off".
At idle, the lower RPM's also mean lower oil pressure.
It may be the sender you replaced has a higher threshold for pressure which isn't being met by your engine at idle.
The other thing, is that it should be either off or on rather than flashing. It may be you bought a defective part.

 

[Hillis33]

@DragonSubie7
I bought the part off of rock auto which said it fit for my car but deflective part could be it, any way for me to check that before I buy another one?

 

[Hillis33]

This is the link for the part that I got in case its the wrong threshold: More Information for WVE 1S6556

 

[donkpow]

I read your part as correct indicated by RockAuto and WVE. Also the Subaru part number translates to that part. This is the only indication of set point pressure for the switch I can find, 3-9 psi. That's quite a range. I suspect your unit is set higher than what your car produces. For myself, I would probably try a different brand (they are cheap enough) or confirm the warm idle pressure with a temporary pressure gauge plumbed into the system.

 

[donkpow]

I should also point out that my manual (2010 MY, N/A, A/T) calls for a switch activation @ 2.1 psi.

 

[Natedog]

As @donkpow said, and personally I'd replace with a Subaru switch after verifying oil pressure at differnet engine rpms with a temporarily installed gauge.