Oil pressure switch wiring.

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dustinwinkle

New Member
Messages
6
I was having an issue where the oil pressure would randomly drop to zero then come right back to normal. I replace the sending unit and had the same issue. Several months later the gauge stops reading any pressure. I confirmed oil pressure with a manual gauge. I again replaced the oil pressure sender with a new one and still show no oil pressure.

The gauge will move up slightly when the ignition is turned on so I do not think it is the gauge. I am thinking it is a wiring issue.

Does anyone have experience with the oil pressure switch wiring? Does the wire go directly to the gauge or does it go through a module? Any help or direction is greatly appreciated!
 
Zep

Zep

Moderator
Messages
9,332
I believe it is connected directly to the gauge, which then has a circuit to switch on the warning light if the pressure is low.

It works through resistance, a small voltage is sent through the wire connected to the sender, and the variable resistance changes the reading on the gauge.

I would start are they beginning:

When the sender was changed was the wire connected to terminal G on the sender (not WK)

Have you checked the earth straps from the bell housing to the body, others have had an issue with this.

If you can, get a 10 ohm resistor and link the sender wire to an earth point on the body. The gauge should read 5 bar.

My money, for what it’s worth, is on the earth strap.
 
hladun

hladun

Member
Messages
150
On the 3200 (only wiring diagrams I have) the oil pressure signal goes to the CAN module and then to the instrument cluster. The 4200 is probably similar.
 
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dustinwinkle

New Member
Messages
6
Thank you for the replies!

I verified earth straps are in place. I added additional earthing to the block for testing.

I used a 10 ohm resistor between the wire and an earth, multiple places on the body and the engine, even back to the battery. No movement of the needle. I tried other various resistors to see if anything would move the needle, nothing did.

Any other suggestions or tests before I pull the instrument cluster?
 
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dustinwinkle

New Member
Messages
6
I have pulled the cluster and done a ton of testing. Gauge out of the cluster, it works fine. Pegs at full ground and goes to various levels with different resistors.

Sensor wire does not go directly to the cluster, it must split off to a module somewhere as it also feeds the red warning light and the blinking light mid cluster.

Gauge out of cluster and connecting directly to the pressure switch, the gauge does not work, which points to a bad pressure sensor.
Gauge in cluster with manually adding resistors and the gauge does nothing, this points to whatever module is controlling the cluster.

I have a hard time believing both have failed. But testing seems to point to that.

Does anyone know which module the oil pressure signal goes through?
 
Zep

Zep

Moderator
Messages
9,332
Good work on getting this far, your methodical approach seems to have narrowed it down well.


There aren’t any wiring diagrams for the 4200 in circulation that I know of. It sounds like from a post above, it should be similar to the 3200 and go to the can module. This might be the place to start looking.
 
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dustinwinkle

New Member
Messages
6
Posting the resolution. I started over and retested everything again. Seems I had multiple bad senders, even one that was brand new. Purchased another new unit and all is working good.
 
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