Riddle me this????

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coldtaco

coldtaco

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Ok, here is another issue that has been perplexing me for a long time and finally am getting around to trying to find an answer.
Anyway: How come my aux oil pressure needle reading, at say 60psi, jumps up about 10psi when I turn the lights on? These gauges are lighted, but I'm pretty sure that the lights are totally independent of the gauge mechanisms.
 
coldtaco said:
Ok, here is another issue that has been perplexing me for a long time and finally am getting around to trying to find an answer.
Anyway: How come my aux oil pressure needle reading, at say 60psi, jumps up about 10psi when I turn the lights on? These gauges are lighted, but I'm pretty sure that the lights are totally independent of the gauge mechanisms.
Click to expand...

It has someting to do with the headlights drawing the power. I had a temp gauge once that would jump 10 degrees with the lights on even though nightime was cooler.

Oil pressure gauges have a very thin sliver of metal that deflects when ....

aw Stone where are ya when we need ya??:D
 
Hi Stephan:

On most gauges, the light bulbs are independent as you have noted, having their own (+) and (-) wires to connect to power.

I'm assuming that your gauge is an electronic gauge though and is not a purely mechanical one. In which case, where did you tap your (+) power to power the signal amplifier box for your gauge? If you look at that, and if it's somehow connected or interfered with by the light system, then you'll have your answer. As the part name suggests, "signal amplifier" will exaggerate any interference or fluctuations that is fed to it.

If you want a clean power source, have a good ground, and connect directly to 12 or 24V that has no other circuits attached to it. Direct to battery would be best, depending on how your system is set up. Maybe a relay with keyed ignition to turn it on and off if you need that.
 
Come on you guys everyone knows that there is a direct hydraulic connection between the oil pressure and the alternator via the vacuum pump. When you flick on your lights it loads up the alternator and slows it down which in turn lowers the oil pressure. Its simple physics.

Just kidding and I just had to take the opportunity to poke fun.

Karl
 
First, it happens wether you at idle or driving.

Stone, without taring my dash apart, which I probably will have to do, I am trying to remember where I took the + power for the oil pressure, but I don't think it was off of a light wire, I could be wrong though. Will bear some investigation.
Would having the ground wire for the pressure gauge hooked to the same place as the ground wire for the gauge lights cause the same effect?
 
coldtaco said:
Would having the ground wire for the pressure gauge hooked to the same place as the ground wire for the gauge lights cause the same effect?
Click to expand...

Sharing a ground for some reason can sometimes cause interference problems. Drill a hole on a well grounded piece of metal and ground only your gauges to that and see if that does something. Or else do what GB did.
 
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