I guess I'm an idiot

DanS911 · DanS911's Garage

My oil pressure warning light isn't working.........I really don't know why.
I tested and there is power to BOTH leads! Is that right??

DUK · 04-05-2010, 04:24 PM

Not certain but I believe the sensor is a grounding point, shouldn't have any current.

Are you sure your checking it right? I've been known to have the voltmeter on ohms instead of volts. lol

DanS911 · DanS911's Garage

That's funny! I actually went back out to the garage to check the meter!

No, I am checking for current at the wire ends that attach to the light bulb in the gauge.
Both have current, when I take the bulb out and put current to one terminal and ground the other the bulb lights up.

Flat6pac · 04-05-2010, 04:46 PM

I recently built a 3.2 that got a new idiot light switch and it does stay on on start up until it trips at 1500 to 2000rpm.
I had a few last year or two that leaked until I just threw all away, theyre a pain to change once the engine is in the car especially on a 3.0.
Bruce

DUK · 04-05-2010, 04:50 PM

Sounds like we have a wire crossed or shorted. Just my .02

ossiblue · 04-05-2010, 06:07 PM

What are the colors of the two separate wires connected to the light?

James Brown · James Brown's Garage

With the engine off and the ignition on the light should be on meaning it a complete circuit. so you could see power at both ends (current flow). Better to check if the switch works. Attach a meter to both posts on the switch, with the engine not running, it should read 0 ohms, when you start the engine it should read infinity. Then you know that the switch works. now check the wires from ground to the light in the dash to power.

dshepp806 · dshepp806's Garage

Quote:

Originally Posted by James Brown

With the engine off and the ignition on the light should be on meaning it a complete circuit. so you could see power at both ends (current flow). Better to check if the switch works. Attach a meter to both posts on the switch, with the engine not running, it should read 0 ohms, when you start the engine it should read infinity. Then you know that the switch works. now check the wires from ground to the light in the dash to power.

+1.

I would say that 12 volts on both sides of the bulb contacts makes for non-glowing bulb, no?

Current is measured in series.

Hooking up VOMs to voltage potentials, while positioned on the OHMs scale will eventually take it's toll on the meter,...ALWAYS verify your scale selections BEFORE making the connections..

Best,

Doyle

DanS911 · DanS911's Garage

[QUOTE=dshepp806;5280063]+1.

"I would say that 12 volts on both sides of the bulb contacts makes for non-glowing bulb, no? "

Correct, that is exactly the case. My question is how does the light go on when the key is turned? Does that ground one of the sides or is something else screwed up?
Anybody else have their speedo out so you can check for current at the oil pressure light?

gshase · 04-07-2010, 06:58 PM

No you are not. An idiot would not worry about fixing it.

steely · 04-07-2010, 07:21 PM

To your question, yes, the switch provides a ground path to complete the circuit.

Does your light in fact turn on when the key is turned? (but without starting the engine?).

If so, it sounds like your circuit is working - since as James Brown pointed out, the switch is closed (meaning no oil pressure).

On engine start, pressure should be ok, switch opens, (no current) light -> OFF (and you can still have +12V at either side of the bulb).

Unless you're saying you have a known oil pressure issue and no light.

T77911S · 04-08-2010, 04:51 AM

dont think in terms of current. the only way, well not really the only way, to measure current is to put an amp meter in series with the circuit. the other way is to measure a voltage drop across a known resistance then its E/R=I.
you want to look for voltage. the reason you see or measure votlage on both sides of the light is becuase the one side is not grounded. voltage looks for the least resistance to ground, if say the P switch is bad, or open, then the meter becomes the path to ground and it measures the full 12v. if the P switch were good and closed and providing a path to ground, the meter would read 0v. most people like to say you have something shorted, but in this case you have an open. it may be the P switch is not closing or a broken wire or a ground wire came off. when something is shorted, you are generally blowing fuses or you will have a constant drain on the battery, depending on if the short is before or after the load, IE- light bulb, radio, etc.

if you have a test light, it is easier to use