Oil Light ON

[flash75]

Good to hear it was easy and not expensive. I was going by the wiring diagram when
I responded to the light being on/off, I don't see how it would be on with the sender disconnected. Perhaps there is some feedback that isn't shown in the wiring diagrams.
I plan to check mine the next time I go under the car.

Clifton

 

[Maxx Mazda]

Good to hear it was easy and not expensive. I was going by the wiring diagram when
I responded to the light being on/off, I don't see how it would be on with the sender disconnected. Perhaps there is some feedback that isn't shown in the wiring diagrams.
I plan to check mine the next time I go under the car.

Clifton

When there's pressure, the circuit closes to ground and the light goes off. Hence when you unplug it, the circuit is open = light stays on.

 

[slavrenz]

Good to hear it was easy and not expensive. I was going by the wiring diagram when
I responded to the light being on/off, I don't see how it would be on with the sender disconnected. Perhaps there is some feedback that isn't shown in the wiring diagrams.
I plan to check mine the next time I go under the car.

Clifton

Without looking at the wiring diagrams, it would be pretty dumb for the oil light not to come on if the sender is disconnected. Just think of it as a safety feature that alerts you that something is amiss. Like if your ABS isn't working, the light comes on to tell you that something's up.

 

[flash75]

"When there's pressure, the circuit closes to ground and the light goes off. Hence when you unplug it, the circuit is open = light stays on."

According to the Protege wiring diagram it's the opposite of what you say. It's on page 46of the wiring diagram. The diagram shows the switch must be closed for the light to be on. It's on the ground side of the bulb. On page 47 of the wiring diagram there is a note "Oil pressure switch, Closes when the oil pressure is low."

The Protege shop manual shows the shows the instrument cluster wiring diagram on page 09-22-2 and the circuit is the same as in the wiring diagram manual.

On page 09-22-13 of the shop manual is the oil pressure switch inspection (Quote)
"1. Verify the oil pressure warning light iluminates when the ignition switch is turned to the ON position.
2. Verify the oil pressure warning light goes off when the engine is started.
If the oil pressure warning light does not iluminate or remains iluminated, inspect the
oil pressure warning light bulb and related wiring harness.
If the oil pressure warning light bulb and related wiring harness are normal, inspect
the oil pressure. (See 01-11-2 OIL PRESSURE INSPECTION.)
If the oil pressure is normal, replace the oil pressure switch."

"Without looking at the wiring diagrams, it would be pretty dumb for the oil light not to come on if the sender is disconnected. Just think of it as a safety feature that alerts you that something is amiss. Like if your ABS isn't working, the light comes on to tell you that something's up."

Your comment make sense but most all the lights will run through a self check when the ignition switch is turned on. I'm just going by the wiring diagrams and what they show.

Clifton

 

[slavrenz]

"When there's pressure, the circuit closes to ground and the light goes off. Hence when you unplug it, the circuit is open = light stays on."

According to the Protege wiring diagram it's the opposite of what you say. It's on page 46of the wiring diagram. The diagram shows the switch must be closed for the light to be on. It's on the ground side of the bulb. On page 47 of the wiring diagram there is a note "Oil pressure switch, Closes when the oil pressure is low."

The Protege shop manual shows the shows the instrument cluster wiring diagram on page 09-22-2 and the circuit is the same as in the wiring diagram manual.

On page 09-22-13 of the shop manual is the oil pressure switch inspection (Quote)
"1. Verify the oil pressure warning light iluminates when the ignition switch is turned to the ON position.
2. Verify the oil pressure warning light goes off when the engine is started.
If the oil pressure warning light does not iluminate or remains iluminated, inspect the
oil pressure warning light bulb and related wiring harness.
If the oil pressure warning light bulb and related wiring harness are normal, inspect
the oil pressure. (See 01-11-2 OIL PRESSURE INSPECTION.)
If the oil pressure is normal, replace the oil pressure switch."

"Without looking at the wiring diagrams, it would be pretty dumb for the oil light not to come on if the sender is disconnected. Just think of it as a safety feature that alerts you that something is amiss. Like if your ABS isn't working, the light comes on to tell you that something's up."

Your comment make sense but most all the lights will run through a self check when the ignition switch is turned on. I'm just going by the wiring diagrams and what they show.

Clifton

Doesn't this support the notion that the oil light may be illuminated if there is a problem with the sender?

I realize that you're just reading the wiring diagrams, but I don't feel like downloading them right now (yay for lazy )

 

[Maxx Mazda]

Doesn't this support the notion that the oil light may be illuminated if there is a problem with the sender?

I realize that you're just reading the wiring diagrams, but I don't feel like downloading them right now (yay for lazy )

Honestly man, I'm not gonna go that far into it. I dont even have my oil light anymore, I use a seperate gauge altogether. The light comes on if it's unplugged. Leave it at at that.

 

[flash75]

"Doesn't this support the notion that the oil light may be illuminated if there is a problem with the sender?"

Yes, it does support that the light may be iluminated if there is a problem. It depends on what the problem is. If the switch has a short to ground the oil pressure light will iluminate. If the contacts are open and will close the oil pressure light will NOT iluminate.

If you go back and read my comments, I said the light will not iluminate under any condition if the sender wire is disconnected, never said anything about trouble indications. About an hour ago I disconnected the sender wire on my 2002 P5, turned on the ignition switch and there was no oil pressure light. I checked the resistance between the oil pressure sender terminal and ground. It showed about 1 ohm indicating the sender contacts are closed with no oil pressure.

"The light comes on if it's unplugged. Leave it at at that."

That may be true for your car. On my car the light is out when the wire is unplugged. I purchased my car new and it's totally stock. I have to assume what I see is is correct since it agrees with the wiring diagrams in two different Mazda Protege manuals.

Clifton

 

[Wagonbacker9]

(bang)

open circuit (be it physically open, or the switch open) = no sensed oil pressure = oil light on... end of discussion. lol

somewhat counterintuitive.. but closing the oil pressure circuit opens the indicator light's circuit.