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Old 12-10-2012, 07:12 PM   #1
madmike13subie
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Default Oil pressure /light

2004 Wrx mods Catless downpipe 3in cat back Cobb intake I have 125k stage 2 flash on it my problem is now on these colder days if I let my car sit for 1 day or 2 days with no starts when I go start the car the oil light is on very slightly and dime once I let the car warms up light turns off not sure if it is the oil pump acting up or getting weak !?!? Any input would be good
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Old 12-10-2012, 07:29 PM   #2
rocketperson7
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there's a bad connection between the sensor and block

you can either-
1. leave it alone
2. take the sensor out, put it back in
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Old 12-10-2012, 07:48 PM   #3
TwoFifty
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Quote:
Originally Posted by rocketperson7 View Post
there's a bad connection between the sensor and block

you can either-
1. leave it alone
2. take the sensor out, put it back in
** Edited because my last post seemed kind of douchey lol!! **

Of course a connection issue is completely possible, I was in no way doubting that... However in MY opinion though id never assume a diagnosis with my oil light regardless of dim, bright, flickering or solid. If the light comes on id be verifying that I actually have correct oil pressure when the light is on. If pressure is within spec even when the light is on dimly then your probably safe to assume its a connection issue.

Last edited by TwoFifty; 12-11-2012 at 08:19 PM.
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Old 12-10-2012, 09:16 PM   #4
KillerBMotorsport
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Quote:
Originally Posted by rocketperson7 View Post
there's a bad connection between the sensor and block

you can either-
1. leave it alone
2. take the sensor out, put it back in
^ This right here.

If the pressure switch is low pressure activated the light comes ON, not dim. The pressure switch has only been activated if it's as bright as when you turn the key to the 'on' position (engine not running).

When the connection between block and sensor becomes corroded the light will come on faintly. It can even vary in intensity if it gets wet/dry or hot/cold.
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Old 12-10-2012, 09:54 PM   #5
madmike13subie
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thanks guys
i have noticed wet and cold weather has caused the light to be on very slightly i plan to check the connection tomorrow at work hope its not the oil pick up :/ how often do u guys see them crack ?
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Old 12-10-2012, 10:19 PM   #6
rocketperson7
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Quote:
Originally Posted by TwoFifty View Post
**** rocketperson7
ok champ
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Old 12-11-2012, 10:12 AM   #7
CrashTestRacer
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Quote:
Originally Posted by KillerBMotorsport View Post
^ This right here.

If the pressure switch is low pressure activated the light comes ON, not dim. The pressure switch has only been activated if it's as bright as when you turn the key to the 'on' position (engine not running).

When the connection between block and sensor becomes corroded the light will come on faintly. It can even vary in intensity if it gets wet/dry or hot/cold.
This doesn't make much electrical sense to me. If I disconnect the wire the light is off, right? Open = off.
So if the connection to the block is bad, then the switch would still have to trip low to allow any current (that can pass through the faulty connection) to pass to illuminate the dash light, no?

In particular, your comment that "If the pressure switch is low pressure activated the light comes ON, not dim." I assure you that a bad connection with a low pressure trip can be dim with a bad connection.
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Old 12-11-2012, 11:48 AM   #8
KillerBMotorsport
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Originally Posted by CrashTestRacer View Post
This doesn't make much electrical sense to me. If I disconnect the wire the light is off, right? Open = off.
So if the connection to the block is bad, then the switch would still have to trip low to allow any current (that can pass through the faulty connection) to pass to illuminate the dash light, no?

In particular, your comment that "If the pressure switch is low pressure activated the light comes ON, not dim." I assure you that a bad connection with a low pressure trip can be dim with a bad connection.
I don't have the schematic for the circuit and sensor in front of me and EE is not my forte, but IIRC the switch is notrmally open. The same condition exists when you disconnect the wire, circuit incomplete = no light. If you ground the wire going to the sensor, either with the raw wire or using the sensor the light goes ON (assuming there is no pressure present).

The switch is of the type that is is either open or closed, there is no in-between. If the switch was faulty it would light, or not, no dim. If the connection is poor the light will be dim, but I think there are some symantics that need to be called out here too...

The 'brightness' during a low pressure condition (ideal connection to the block or less than ideal) will be as bright as when the key is turned to the ON position (without the engine running). As far as I've ever seen, this is unmistakably brighter than just a poor connection where the light comes on very dim.

There was an EE that spelled all this out much more eliquently than I'm butchering it here, but I can't find that thread for the life of me right now

Bottom line... remove sensor, reinstall and watch light. If it was a poor connection to the block you light problems should be gone.
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Old 12-11-2012, 12:36 PM   #9
CrashTestRacer
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Hmmm... Here's what I'm assuming:
The connection is +V to the dash lamp with the other side of the dash lamp going out to the sensor which will sink to ground and allow current to flow if the switch is made. The switch is open when pressure is applied, and will close if there is not enough pressure. There must also be a another sink to ground connection from the lamp to illuminate the light with the key in accessory.

I'm with you that if the light is on dim, there must be a poor connection to the block since it is an unlikely failure mode for the switch to only be somewhat made (with resistance). If it fails, it probably just fails open or closed. The accessory method of turning on the light still has it's own good connection to ground, so full brightness there. It's a good test for a bad block connection.

What I don't see is how the light would be on at all unless there is low oil pressure allowing the switch to be closed in the first place. It's a series connection - you have to have low pressure (or a bad switch) for that light to be on, don't you?

I know I wouldn't be driving this car even if this is 99% not a real problem, that's for sure...but I just got done rebuilding my engine, so I know how painful it is
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Old 12-11-2012, 02:38 PM   #10
tachrev
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Had mine come on dim as well after washing the engine bay.

Letting it dry out solved the problem, and it did not come back.

Just giving you some firsthand experience with a similar issue.
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Old 12-11-2012, 07:00 PM   #11
CrashTestRacer
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That actually sounds like the conductor is shorting around the switch to the engine block. That would make more sense to me than a bad sensor to block connection.
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Old 12-11-2012, 07:46 PM   #12
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Moisture shorting or poor connection make LEDs frequency of switching on and off apear as a dim light rather then normal all or nothing.

All as in turning the key and all displays cycle. Thats the FULL bright level to be wary of.

Or was exactly my cases of wet sensor/ dim light.
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Old 12-11-2012, 10:34 PM   #13
madmike13subie
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Wow really good info and experiences here thank You everyone haven't had the light issues again yet hasn't rained a good amount yet plan to check sensor tonight will report back
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Old 12-13-2012, 01:31 AM   #14
dictoresno
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i have the same issue sometimes, like 2 or 3 times a year maybe. and its only on humid hot days first thing in the morning when i first start the car. goes away once it dries out.
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