Lost the Druck Press Gauge 12V

[magnumpi]

In trying to diagnose my druck press/oil pressure sender gauge pegged at 5 since I got my car this summer, I just pulled the gauge out and put a voltimeter to her and discovered that the red/black 12V wire which feeds the pressure druck press is missing it's juice. I know from reading posts that this wire should read when turning the key to acc, is this not correct?

So basically, somewhere this wire is cut/doesn't reach the fuse box. I checked the back of the light switch and everything is looks fine, and all my other gauges, including oil temperature, work fine (reads 12 V when key on).

Can I tap into the 12V feed for the oil temperature, splice the wire off and put two wire connectors, or will the result be TWO messed up gauges?

Thanks!

Dan

[scotricker]

Dan,
have you checked the wires at the sending unit?
My gauge was acting all wild, and it was just not connected securely at the sending unit. easy fix. hope that's it.

[magnumpi]

Hi Scot,

Thanks for your suggestion. I checked continuity on the green/red wire that leads to the sending unit, it was OK. I believe there's defintely something wrong if I can't read any power going to the gauge itself via the red/black wire. This must be causing the "pegged at 5" condition as soon as I turn the key to acc, I'm guessing.

Dan

[3.2 CAB]

I would have to believe that something other than no power reaching the gauge. If the gauge had no power to it at all, I do not think that the gauge would have ANY movement at all. With it pegging out at 5, or actually even a little bit above 5, it would indicate to me that power is reaching the gauge, and that either the green wire is not making full contact to the sending unit, or that the sending unit is bad. Good luck, Tony.

[Flat6pac]

On a Carrera, you need to deform the connector so it touches well enough to ground.
Bruce

[Formerly Steve Wilkinson]

My oil pressure gauge pegs at the top when I turn the key on and then reads absolutely normally as soon as the engine fires. Don't know what the problem is, but I don't much care...

[Walt Fricke]

The internal design of the gauge is such that if the signal wire (the one connected to the sender back at the engine) has infinite resistance (as in it is broken, or disconnected), the gauge will peg (at least assuming the gauge has 12V to it, and the gauge ground is OK also).

3.2 has it right about power - if no power is reaching the gauge from the front/battery side of things, the needle won't budge.

The gauge itself is a rheostat - there is a wire coil inside, with a sliding contact. Low pressure, little resistance, higher pressure, more resistance. I'd guess Steve's sender is going bad - something is amiss at the zero pressure end of things inside the sender - maybe guck on the windings. When there is pressure the slider moves to a competent part of the windings. He could check this theory with an ohmmeter to his gauge, or by grounding the sender wire somewhere - at gauge or at sender - and turning on the key without starting.

Bruce - what connector on the 3.2 needs to be bent?

Walt Fricke

[spuggy]

Originally Posted by 3.2 CAB

I would have to believe that something other than no power reaching the gauge. If the gauge had no power to it at all, I do not think that the gauge would have ANY movement at all. With it pegging out at 5, or actually even a little bit above 5, it would indicate to me that power is reaching the gauge, and that either the green wire is not making full contact to the sending unit, or that the sending unit is bad. Good luck, Tony.

+1 what he said.

[magnumpi]

Yes, the gauge is pegged "above the five" so it must be getting power, perhaps I need to invest in a better voltometer.

I just grounded the green/red wire at the sender and the needle drops down, so now I think it has to be the sender....new one just ordered.

Dan

[mthomas58]

Lots of info about pegged gauge here:

Ground locations for Oil Pressure Sender & Pressure Gauge?

Another Oil Pressure Sender Replacement Thread with pics

Oil pressure gauge stays stuck at the top...

[Walt Fricke]

Amidst the good info Mark gives links to is a bit of misinformation. One poster asserted that if you disconnect the sender wire at the gauge, and with the key in a certain position (not in the full off-remove key position) the gauge should read 0. This is incorrect.

A failed sender, a disconnected sender, a broken wire at the sender, a bad connection at the sender, a broken connector at the gauge, any break in the sender wire, or a sender wire disconnected at the gauge - all of these will result in a pegged gauge (pegged = max reading) as long as 12V is getting to the gauge.

If the internal gauge connection to the sender lug is broken, same result. But I would put gauge issues way way way down on the list. Bad connections and failed senders are the usual suspects. Pretty easy to differentiate between the two.

Walt