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catmastertech, Technician
Category: Construction and Road Equipment
Satisfied Customers: 2366
Experience:  Field service technician for CAT 19 years.
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Oil pressure gauge problem. gauge peaks clockwise as soon as

Customer Question

oil pressure gauge problem. gauge peaks clockwise as soon as key turned on, even when sending unit unplugged. and light on dash stays on.???
Submitted: 2 years ago.
Category: Construction and Road Equipment
Expert:  catmastertech replied 2 years ago.

If a gauge is pegged out in either direction it often means the signal wire is either open (broken) or shorted to ground.

Disconnect the signal wire on the back of the gauge to see if it stays pegged out. If it does, then try shorting the signal wire to ground, this should peg the gauge in the opposite direction. The results will indicate the signal wire is shorted or open.

If you need more help on this, please post the make, model and serial number of this machine. I can help you with CAT machines but, I do not have resources for any other brands.

Customer: replied 2 years ago.
d4g xl 2004. ser# ***** oil pressure gauge pegged ccw with ignition off, pegged clockwise with ignition on,warning light stays on with ignition on and goes off when key turned off. all this while engine is not running.
Expert:  catmastertech replied 2 years ago.

Thanks for the serial number.

I would begin by testing the connection from the dash connector at pin 13 of the chassis harness to the gauge. Connect your ohmmeter to the grey wire of the sender and pin 13, it must read less than 5 ohms resistance for a good connection.

One area I find the most trouble is below the step on the left side of the cab. Remove the step cover plate and locate the two 12 pin connectors. One will have the grey wire at pin #2. This is the oil pressure wire. It is marked 464 Inspect the connector and the pins for corrosion. I have found them damaged often. If it is not at that location check for continuity from the step connector to the dash and the other side to the sender. (disconnect the sender for correct reading)

Also disconnect the warning light module, this has been updated a few times and could cause a short that would affect the gauge.

The lamp is on a different oil pressure switch and is a grey wire marked F400. This wire is at pin #7 of the other step connector and pin #21 at the dash connector.

If you need more help, please let me know.

Customer: replied 2 years ago.
fuel guage did not work jumped from ign to fuel guage disconnected jumper wire fuel guage now works but now have oil guage problem
Expert:  catmastertech replied 2 years ago.

Fuel gauge is not connected to the warning module and should not be damage by that,

All gauges and the module share the same power feed (white wire marked 123) and ground (black wire marked 200). If you shorted the gauge ground leg, that may have damage the module.

All these gauges work when the sender or switch provides ground. You should never test the gauges with power, only a ground or no ground will make the gauge needle swing.

Warning lamp is on when it has no ground and off when ground is present.

Here are the ohm reading values for the oil pressure sender to the gauge.

227 to 257 @ 0 to 21 kPa (0 to 3 psi)
192 ± 27.5 @ 48.3 kPa (7 psi)
102 ± 11 @ 276 kPa (40 psi)
21.5 to 49.5 @ 552 kPa (80 psi)

This means grounded wire will peg the gauge to high side, open circuit will peg gauge to low side.