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Old 12-28-2004, 02:57 AM   #1
Scooby Newbie
Member#: 33135
Join Date: Feb 2003
Default Megan Racing oil pressure gauge install

Anyone install a Megan Racing oil pressure gauge before? We just unscrewed the stock oil pressure sensor and put in the MR sending unit. Then wired up the gauge. Red to 12v ignition, black to ground, purple to ground and orange directly to the sending unit. The gauge lights up fine, but the reading is wack. It jumps around when we hit the headlights and also sits at 0 and fluctuates around. Did we wire it wrong? On the instructions it says to hook the gauge up to ground on the sending unit... but there's nothing on the unit to ground. Can anyone help? Thanks
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Old 12-28-2004, 10:55 AM   #2
Scooby Specialist
Member#: 5887
Join Date: Apr 2001
Chapter/Region: BAIC
Location: Fremont, CA USA
2002 GDAA (bugeye)
797 (blaze yellow)


Without access to the datasheet of the components (which I doubt is provided to the end user), it's hard to say what the exact cause could be. I'm a bit familiar with industrial pressure measurement equipments, and I imagine the same technology is used for automotive pressure gauges. Having said that, afaik, most pressure gauges use one of 3 types of transducer (commonly called "sender" here), and then wired into a Wheatstone bridge configuration, which requires power and ground connections.

Different types of transducers also have different levels of susceptibility to noise and power source voltage fluctuations. Within each type, there are different quality grades in terms of reading accuracy. Those with a higher susceptibility to voltage fluctuations will exhibit fluctuating readout as the voltage source varies. In the presence of other electrical components, the "+12V" source fluctuates somewhat.

There are 2 possibilities I could think of for the moment:
(1) There may be intermittent connection problem, introducing intermittent readout error. In this case, re inspecting the wiring should solve the problem.

(2) The quality (in terms of sensitivity to noise and voltage source fluctuations) and type of the transducer is such that whatever voltage fluctuation that exists in your vehicle, either due to the standard components or additional electronics, creates the fluctuations in your reading. In this case, replacement of the sender with a compatible one (in terms of the output range) and of a better quality should resolve the issue. But I wouldn't recommend trying other senders unless you know it is a compatible type.

Perhaps you could get better luck if you ask the manufacturer.
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