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Old 08-20-2009, 02:59 PM   #1
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Default Oil pressure warning buzzer

So, I know I've seen a thread about this before but I couldn't find it. I'm wanting to set up a piezo buzzer that will go off when oil pressure drops. I'm thinking that I can wire up a 12v source to one side of the buzzer and the ground to the oil pressure sender. If the voltage for the oil pressure sender drops, the voltage difference will be high enough for the buzzer to go off. Does this make sense to anyone else?
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Old 08-20-2009, 03:50 PM   #2
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Makes sense to me. I've thought about doing the same. Understand that the buzzer will sound when the engine's not running and the key is on. Maybe tap the 12v off the fuel pump or some other "while engine running" source. May avoid some of the nusiance.
--Alex
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Old 08-20-2009, 03:52 PM   #3
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Makes sense to me. I've thought about doing the same. Understand that the buzzer will sound when the engine's not running and the key is on. Maybe tap the 12v off the fuel pump or some other "while engine running" source. May avoid some of the nusiance.
--Alex
Yeah, i could come off of the fuel pump relay. I dont have my fuel pump set to prime before starting so it would only buzz between the time of cranking and building sufficient oil pressure.
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Old 08-20-2009, 04:22 PM   #4
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If you're using the stock '95 oil pressure sender, then fine- it's a simple on/off switch to begin with. If you've got an analog sender, simply grounding the buzzer through it good.
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Old 08-20-2009, 04:36 PM   #5
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If you're using the stock '95 oil pressure sender, then fine- it's a simple on/off switch to begin with. If you've got an analog sender, simply grounding the buzzer through it good.
Yeah, I'm not doing using the stock sender. I have the true analog sender. If that wont work, I do have a stock sender laying around and i could rig that up with a sandwich plate or something of the sort.
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Old 08-20-2009, 05:06 PM   #6
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You could get a VDO sending unit like the one I am using. It has the variable output for the gauge, and a 7psi switch in the same unit. See my oil warning light from hell thread for more details. Replace LEDs with buzzer, done.
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Old 08-20-2009, 05:20 PM   #7
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Will that vdo drive the stock 93 gauge?
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Old 08-20-2009, 05:31 PM   #8
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I forget which year gauges were actually linear, and which ones need to be linearized (like mine). Check m.n for more details. But yeah, either way it should. That is what I am doing.

EDIT: Oh wait, snap, I think I just linearized the stock temperature gauge, not the stock oil pressure gauge. I did change the position of the oil pressure gauge needle though.

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Old 08-21-2009, 12:25 PM   #9
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I'd recommend a bright light instead of a buzzer, as depending on the situation you might not hear one. That's what I have on the Targa car along with an analog gauge. They're driven off a pair of factory senders.
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Old 08-21-2009, 12:58 PM   #10
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I'd recommend a bright light instead of a buzzer, as depending on the situation you might not hear one. That's what I have on the Targa car along with an analog gauge. They're driven off a pair of factory senders.
Maybe I will do both. I'm a belt and suspenders kind of guy. I'm afraid that on a bright day I might not see a light. I would think I would hear a 108db buzzer.
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Old 08-21-2009, 01:45 PM   #11
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Alright, so, I've been thinking. I am in the process of megasquirting a buddy's 91 TBI firebird, and I have noticed something very intriguing. The fuel pump relay is tied in with the oil pressure sender. Therefore, if the oil pressure pressure drops, the fuel pump shuts off. Now, this wouldnt instantly kill the motor as there would still be fuel in the lines. Also, this may not be good for a boosted car because you would go lean for a second until the car died. However, if you could tie it into another relay like ignition power or something like that, then you could have the car automatically die if you lose oil pressure. The problem I see is that the car wouldn't start until you had cranked long enough to get oil pressure, but maybe that's not such a bad thing.
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Old 08-21-2009, 01:57 PM   #12
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you could set up your spark or fuel cut to be actualized by the oil pressure signal. dont ask me how specificly but it should be possible.
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Old 08-21-2009, 02:32 PM   #13
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You'll need some sore of delay in there to ensure you can start the car. No oil pressure initially means the OP switch will be open leading to a no start. Unless the switch is low enough to read cranking OP maybe?
--Alex
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Old 08-21-2009, 02:37 PM   #14
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that vdo sending unit will complete the circuit at 7psi. I would think that there would be 7psi of oil pressure during cranking. If not, you could have a bypass button that you have to hold until it builds pressure.
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Old 08-21-2009, 03:49 PM   #15
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Ah, good call. Just disable the circuit under cranking. That'll do it.
--Alex
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Old 08-21-2009, 05:57 PM   #16
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Some of the circuits in the dash fuse panel are not hot during cranking, like the radio circuit. Use an add-a-circuit and get power for the buzzer from there. That will help.

I still prefer the light, or at least both. The LED array I used for mine is really bright, and in the top center of the gauge cluster. If you are looking forward, you will see it.
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