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Whaledriver

New oil pressure gauge install issue

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(edited)

I just installed a new VDO oil pressure gauge #350-104 80 psi & VDO  # 360- 006 10-180 ohm 80psi pressure sensor. I hooked up the "+" side of the gauge to the same power supply that illuminates the gauge pod lights. I wired up the gauge "S" labeled side to the "G" on the sensor. I ensured that the sensor threads were clean during install on the engine, hopefully to ensure a good sensor ground. My problem is that as soon as I turn  my ignition to "on", the needle on the pressure gauge goes off scale on the high side. With the engine running, and showing a false high off scale, If I remove the ground from the gauge, the needle drops down below the zero side. I have checked that all the leads contacts are tight. The only thing I haven't done is run an ohms continuity check on the G wire.   Any suggestions on solving my issue?

Edited by Whaledriver
spelling

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Sounds like you have a short.

 

What happens when you disconnect the wire at the sender?

 

Check you don’t have any stray strands of copper wire sticking out of a crimp and contacting ground or the sender body. 

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The lights should be on a different power supply than the gauge power for the sender. The sender power “+” is powered when key is turned to run. Not to the pod lights


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(edited)
20 hours ago, Preyupy said:

There is a ground wire to the gauge also

 

20 hours ago, Schnellvintage said:

The lights should be on a different power supply than the gauge power for the sender. The sender power “+” is powered when key is turned to run. Not to the pod lights


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I apparently assumed wrong that, since the pod lights only illuminate when the key is turned on,   just tapping the hot power source to the pod lights was OK.  Are you recommending  running a separate wire from the ignition to the "+" side of the gage will solve my pegging out issue? Additionally, anyone know what the normal psi range is on this 73 engine? The puzzling thing is, that the needle pegs out when I turn the ignition on without the engine running! How does that relate to gage pressure range capability?

Edited by Whaledriver
added needle peg out

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It should.. as the lights go to ground through the bulb... you can use the ground for for both,the other side of the gauge’s bulb and the sender side ground..


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You got the wrong gauge range.  Need 0-150psig.  Oil pressure when cold hits 90 psig or so.

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8 hours ago, jimk said:

You got the wrong gauge range.  Need 0-150psig.  Oil pressure when cold hits 90 psig or so.

That makes sense. I didn't realize the oil pressure went that high.  In other words, my installed wiring is ok and  that when it goes off scale on the high side, it is probably accurately trying to display a psi beyond the design of the gage that I have installed. Hopefully a replacement solves my issue and I can get on with other improvements to my Roundie.

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What does the gauge read at idle or when the key is on and engine not moving.?
It should be pegged.


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1 hour ago, Schnellvintage said:

Oops shouldn’t be pegged..
Correction


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The gage is pegged, engine off with ignition on  or engine running.

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Its not the gauge... check the wiring again.  3 wires...(+) ign on....(-) chassis ground and same as engine. …(sender wire from ...oil pressure sender)  

Does your sender have 2 connections? light and gauge?

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I think I recall having this same problem when I first tried to install a VDO gauge too.  Bad news is that if memory serves, turned out I somehow incorrectly wired it and sent +12V to the SENDER and fried it.  Not saying you necessarily goofed like I did, but rather consider that the fault might be with the sender and not the gauge.  If you power up the gauge but leave the G wire disconnected, what happens?

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Might have the wires swapped on the sender.  With zero pressure the switch side to the dash lamp makes contact.

Correct gauge is VDO 350-041 for 0-150 psig not 104

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3 hours ago, AustrianVespaGuy said:

I think I recall having this same problem when I first tried to install a VDO gauge too.  Bad news is that if memory serves, turned out I somehow incorrectly wired it and sent +12V to the SENDER and fried it.  Not saying you necessarily goofed like I did, but rather consider that the fault might be with the sender and not the gauge.  If you power up the gauge but leave the G wire disconnected, what happens?

With all three wires connected correctly at the gauge, I disconnected the G wire from the sender and when I turned the key on, the gauge  pegged out on the high side again? 

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