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03-27-2015, 10:22 AM | #21 |
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Re: How to calibrate oil pressure gauge?
Actual oil pressure is not important to me. I just want to know that I have pressure and that it does not change from what is normal for my car. A change from normal, will let me know that something is not right and I better pull over and check it out.
Calibrating the sending unit to the gauge can be done at the sending unit. Incorrect gauge readings can be caused by poor connections or poor grounding.
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03-27-2015, 11:26 AM | #22 |
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Re: How to calibrate oil pressure gauge?
Here's the diagram from the HAMB. As mentioned, poor connections could be an issue as well as tired/broken bimetallic strips or points, or heater coils in both the sender and gauge. Probably a good test is if you can detect a pulsing needle movement in the gauge when turning the ignition on without starting the engine.
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03-27-2015, 12:15 PM | #23 |
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Re: How to calibrate oil pressure gauge?
Henry,
I'd do what Pete suggested....NOS dash gauges are easy to find even at small swap meets. I'm pretty sure the fuel and oil pressure gauges are the same, just change the face. Adding a rheostat to me isn't where it is at, not that anyone asked. Charlie ny |
03-27-2015, 07:40 PM | #24 |
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Re: How to calibrate oil pressure gauge?
I'm Charlie NY on this. Adding a resistor shunt is not the solution. How much of a difference are you trying to eliminate? You might be able to "fix" it by replacing the 80# sender with A 60# unit. A Standard Motor Products PS 60 is a direct fit. It will set you back about $15.00. The electrical part of the sender/gauge system is the the same. What changes is the dial face markings and the sender diaphragm. So if you use a sender with a lighter diaphragm the gauge pointer will move higher on the scale.
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03-27-2015, 08:13 PM | #25 |
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Re: How to calibrate oil pressure gauge?
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03-27-2015, 09:58 PM | #26 |
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Re: How to calibrate oil pressure gauge?
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03-27-2015, 11:13 PM | #27 |
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Re: How to calibrate oil pressure gauge?
Old Henry, try contacting Tom Wesenburg on the model A forums, he is really good on this kind of stuff. Good luck and post back if Tom is helpful, he enjoys a challenge.
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03-27-2015, 11:33 PM | #28 | |
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Re: How to calibrate oil pressure gauge?
Quote:
Thanks for the idea.
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03-27-2015, 11:34 PM | #29 |
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Re: How to calibrate oil pressure gauge?
Yeah, that's why I have the mechanical gauge but I'd still like to get the stock gauge more accurate if I can. The 60# Standard Motor Products sender seems like it might be just the hack I'm looking for. I've ordered that and will try it and see.
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Prof. Henry (The Roaming Gnome) "It is good to have an end to journey toward; but it is the journey that matters, in the end.” *Ursula K. Le Guin in The Left Hand of Darkness Last edited by Old Henry; 03-27-2015 at 11:39 PM. |
04-02-2015, 04:01 PM | #30 | ||
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Re: How to calibrate oil pressure gauge?
Quote:
Quote:
(Yeah, I put the old sender back in. Better to read too low than too high.)
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04-02-2015, 09:24 PM | #31 |
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Re: How to calibrate oil pressure gauge?
Reading to high is easier to deal with on the OP system. If you want to experiment try a 10 ohm resistor in series between the gauge and sender. See if that gets you closer to the mech gauge.
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04-03-2015, 05:37 PM | #32 |
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Re: How to calibrate oil pressure gauge?
Good idea. Even better - I'l put the POT in series. Then I can adjust the resistance and see how much it takes to match the mechanical gauge. If I can get a match I can then just buy a resistor the correct ohms, install it, and have a permanent hack.
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04-04-2015, 02:38 PM | #33 |
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Re: How to calibrate oil pressure gauge?
So, I put the POT in series between the gauge and the 60 lb sender. Same result trying to reduce the current through the oversensitive sender as when trying to bleed current past the stock too restrictive one. No balance was possible. Up to 5.2 ohms the gauge read double just like the sender read without restriction. At or over 5.2 ohms the current shut off and the gauge read zero regardless of the pressure at the sender.
As concluded previously, because the sender is not varying the current like a rheostat or resistor but is actually switching it on and off at varying rapid intervals, varying the resistance between it and the gauge has no effect below 5.2 ohms resistance and cuts off all current above that.
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04-04-2015, 02:52 PM | #34 |
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Re: How to calibrate oil pressure gauge?
P.S. For anyone struggling to remove their oil pressure sender, Snap-on Tools makes this handy tool just for that purpose that works great. Just have to break the spring holder off of it at it gets in the way of our fatter senders. The Snap-on part number is S6156.
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04-04-2015, 04:03 PM | #35 |
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Re: How to calibrate oil pressure gauge?
This may be a little late in the discussion but what about taking both to a calibration lab and having them tested? You may find the mechanical gauge isn't all that accurate either. Your objective appears to be getting an accurate oil pressure reading and judging from the tools and effort you're going to pursue this pretty relentlessly. If you take both to a cal-lab you will have an accurate baseline and from there you can decide how to proceed. There are certified cal labs in the SLC area that work to NIST standards, maybe they can help.
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04-04-2015, 05:43 PM | #36 |
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Re: How to calibrate oil pressure gauge?
Same here. My main concern is when I'm idling at a stop light and my dash gauge says zero oil pressure. If it said anything above zero I'd be fine with it. So, I have to open my glove box and look at the mechanical gauge that never shows lower than 20 psi. That's what I'm mainly looking for - the same as TomO - just to show some pressure on the dash gauge at idle. But, not 40 lbs. that the 60 lb. gauge shows. It's not a big deal. Just a curiosity about whether the stock dash gauge and/or sender can be calibrated in any way. So far it looks like neither can. As I said before, if it continues to bug me I'll just buy a new sender and hope it makes the gauge read more accurately.
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Prof. Henry (The Roaming Gnome) "It is good to have an end to journey toward; but it is the journey that matters, in the end.” *Ursula K. Le Guin in The Left Hand of Darkness Last edited by Old Henry; 04-04-2015 at 10:08 PM. |
04-04-2015, 06:37 PM | #37 |
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Re: How to calibrate oil pressure gauge?
Prof
A 20 pound pressure switch and a small light will do what you want. Have a happy Easter. Bruce
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04-04-2015, 08:42 PM | #38 |
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Re: How to calibrate oil pressure gauge?
Old Henry,
Read post #8. The sending puts out pulses. 120/min. = mid scale on gauge. |
04-04-2015, 10:08 PM | #39 | ||
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Re: How to calibrate oil pressure gauge?
Quote:
Quote:
Yeah, I tested mine right after you posted that and that's about what my gauge does. And I could totally control the gauge with the pot. That's why I thought it might work either in parallel or series but it wouldn't with the cycling switch in the sender.
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04-04-2015, 10:38 PM | #40 |
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Re: How to calibrate oil pressure gauge?
Now you really have my curiosity up. What is are the specifics on the POT you are using? Can you provide the maker and specs on it? estout81 is absolutely correct the output of the sender is pulses. These gauge systems have a slow response. So don't look for rapid changes. The gauge is nothing more than a resistor wire wrapped around a bimetallic strip. More current though that resistor = more pointer movement. Increasing the resistance that the sensor is driving should reduce the pointer movement not kill it. It may be time for me to put together a test station.
I do know the fuel gauge works with a resistance type sender. And the battery voltage (not Ammeter) gauge reads correctly with a 60 ohm resistor in series on 12 volts.
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