Oil Pressure Gauge - Full Sweep Electrical Power Up - Team Camaro Tech
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post #1 of 18 (permalink) Old Dec 13th, 14, 09:51 PM Thread Starter
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Oil Pressure Gauge - Full Sweep Electrical Power Up

I've been getting ready to fire up and break in my new motor for my 69.

After going thru a system check for my electrical I wanted to ask about the power up sequence of my Auto Meter full sweep electrical oil pressure gauge; it's GS series.

Previous to tearing down the car the gauges were working fine. I just don't recall what the sequence of that particular gauge was.

What is happening now is this:

- turn ignition on
- oil pressure gauge- if needle is at zero, it slowly moves to the maximum pressure and stays there. turn key off. turn key , gauge needle is at maximum and then drops to zero and then gradually moves to maximum and stays there, it never rests at zero.

Is this normal? I can't recall if this was the normal sequence. I've checked the grounds and wiring looks good. the sending unit and harness are all in place.

I also have a full sweep electrical water temp gauge ; on power up it doesn't move, which makes me think there's somethjng wrong with the oil pressure gauge.


I'm gojng to prime the oil pump tomorrow and see if I can build oil pressure; maybe the gauge will behave differently with actual pressure?

Can you guys tell me what power up procedure is normal for this oil pressure gauge?
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post #2 of 18 (permalink) Old Dec 14th, 14, 03:32 AM Thread Starter
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Re: Oil Pressure Gauge - Full Sweep Electrical Power Up

Found this :
https://www.camaros.net/forums/showth...l+sending+unit
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post #3 of 18 (permalink) Old Dec 14th, 14, 05:13 AM
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Re: Oil Pressure Gauge - Full Sweep Electrical Power Up

Full sweep gauges will not full sweep on power up! Why?

This is a question/concern that we hear more often these days as many OEM, and some after market gauges perform a full sweep on power up. Auto Meter full sweep (digital stepper motor) gauges will not perform a full sweep. Instead what they are intended to do is a “calibration sweep” which is a little different. Instead of sweeping to full scale and back, the Auto Meter gauge(s) will simply sweep backwards from its last reading to just below the minimum reading, touch the stop pin, then go back up to whatever current reading is. If the gauge is already at minimum reading, you will then see little to no pointer movement, however you may hear a momentary buzz, or grind noise as the stepper motor tries to push the pointer against the stop pin. This is completely normal.

Here are a couple examples: If you shut your engine off and your oil pressure gauge stops at 40 psi, the next time you power it up, the pointer will move down (backwards) to the stop pin just below zero, then back up to current reading when the engine is started. There is no full sweep on power up. If your gauge (lets say a temp gauge in this case) is already on 100 (minimum reading) because the last time the car was run, it was not warmed up. When you power the gauge on, the pointer will simply push back against the stop pin, make a momentary noise and stay there until the sender/engine is warmed up. Again there is no full sweep.

The only exception to all of this, is the (now discontinued) Auto Meter Nexus series. This was a series all by itself that had the a full sweep programmed into it as part of its “opening ceremony”. This opening ceremony, or full sweep can not be programmed into any of the other Auto Meter gauges

http://www.autometer.com/tech_faq_an...x?sid=1&qid=74

Power-Up
The pointer will move backward to the stop pin and then move to the zero box. This procedure is an auto-calibration
function and is performed on every power-up. While this test is being performed, the gauge may make a clicking
sound. This is normal.

http://www.autometer.com/productPDF/2650-1134-00rB.pdf

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post #4 of 18 (permalink) Old Dec 14th, 14, 06:43 AM
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Re: Oil Pressure Gauge - Full Sweep Electrical Power Up

For an electric oil pressure gauge, it will read 0 pressure unless the car is running. I replaced my Stewart Warner mech water temp gauge after the capillary tube broke after 33 yrs and went with a AutoMeter GS Led gauge. The gauge will not move when the car is turned on and the coolant is cold. If you came from a drive and shut the car off and went back out and turned the key but not started it you would get a reading but of a lower temp of course.

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post #5 of 18 (permalink) Old Dec 14th, 14, 06:36 PM Thread Starter
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Re: Oil Pressure Gauge - Full Sweep Electrical Power Up

I did some testing today:

1. Used Multimeter to test that sending unit is grounded. Check

2. Primed the motor and checked for oil pressure. With ignition on, the gauge makes a humming noise and the needle moves full sweep to 100 mark. During priming the needle doesn't move at all.

3. After priming, I let oil return to pan and pulled the sending unit. It was filled with oil. I even tried sucking out the oil and testing it in hand attached to the harness, power up and I get the same reading on gauge.

here's a video of it. Ignition On - full sweep to 100. ignition. Off - returns to zero.

The harness is a pigtail into sending unit and a pigtail at back of gauge. The ground is daisy-chained with the other gauges and grounded to body. The other gauges appear to be working on ignition on.

Any other ideas? thanks in advance.

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post #6 of 18 (permalink) Old Dec 14th, 14, 07:30 PM
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Re: Oil Pressure Gauge - Full Sweep Electrical Power Up

Autometer told me you can't use the same common GND that the other gauges are on. Try a separate GND. I have 2 and asked them about why 2, it needs 2, ok. So I have one to a GND under the dash and #3 in the instructions says a GND close to the sender, so I asked if I can use the back of the drivers side cyl head. Yup. So that's where the 2nd GND is.

http://www.autometer.com/download_instruction/1079A.pdf

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post #7 of 18 (permalink) Old Dec 14th, 14, 08:24 PM Thread Starter
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Re: Oil Pressure Gauge - Full Sweep Electrical Power Up

Thanks Mark. I'll try it before I call them. The gauge setup,and wiring worked fine before I tore down the car, 1.5 years ago. The sending unit has been sitting on a shelf since, not sure if it went bad on that shelf. A replacement unit for it is $108-

Quote:
Originally Posted by COPO View Post
Autometer told me you can't use the same common GND that the other gauges are on. Try a separate GND. I have 2 and asked them about why 2, it needs 2, ok. So I have one to a GND under the dash and #3 in the instructions says a GND close to the sender, so I asked if I can use the back of the drivers side cyl head. Yup. So that's where the 2nd GND is.

http://www.autometer.com/download_instruction/1079A.pdf
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post #8 of 18 (permalink) Old Dec 14th, 14, 08:44 PM
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Re: Oil Pressure Gauge - Full Sweep Electrical Power Up

Don't use teflon tape on the sender threads or it will affect the GND on the sender, only use liquid teflon or if you trust just clean threads which I don't you can do that also.

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post #9 of 18 (permalink) Old Dec 15th, 14, 03:20 AM
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Re: Oil Pressure Gauge - Full Sweep Electrical Power Up

You can test the sending unit with shop air and a regulator.
Hook up ait to the inlet, ohmmeter on terminal and body, slowly apply air, resistance should change.

When installation time comes, fill sender with oil, then screw in.
This action makes for a faster reading gauge as air is compressible.

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post #10 of 18 (permalink) Old Dec 15th, 14, 05:27 AM
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Re: Oil Pressure Gauge - Full Sweep Electrical Power Up

Quote:
Originally Posted by COPO View Post
Don't use teflon tape on the sender threads or it will affect the GND on the sender, only use liquid teflon or if you trust just clean threads which I don't you can do that also.
The Teflon tape affecting the ground on sending units is a myth. The sharp threads easily cut through the tape. The Teflon whether tape or liquid fills any voids and seals.

My guess is a bad sender.

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post #11 of 18 (permalink) Old Dec 15th, 14, 08:51 AM
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Re: Oil Pressure Gauge - Full Sweep Electrical Power Up

Technically, Teflon® tape is a lubricant, not a sealer.
Pipe threads are tapered for a reason - self-sealing.

But yes, I admit, I'm one of the group who uses tape as a sealer...peace of mind.

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post #12 of 18 (permalink) Old Dec 16th, 14, 09:19 AM Thread Starter
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Re: Oil Pressure Gauge - Full Sweep Electrical Power Up

I spoke to Autometer, fwiw it's okay to daisy-chain grounds.

I used a multimeter to test the harness by back probing the purple wire at the sensor. For 0 psi there should be a 0.5 v reading, for 100 psi it will read 4.5v. If there is 0 v, then I should test the gray wire and ensure I'm getting. 5v. This is all from Autometer

So I test the purple wire and get 4v which explains the high reading. I have analog meter so I don't know exactly. Waiting on Digital from amazon.

I also test (back probing) the gray wire at the sending unit and at the gauge, both readings are 5v, check.

However, I get a 0v reading at the gauge end which means there is no continuity in the purple wire from sending unit to gauge.

That is as far as I got before I had to head to work. I will have to check for continuity from gauge to firewall fuse box then firewall to sending unit. I'm guessing maybe the purple wire got pinched between the new firewall insulation and the fuse box when I reassembled? Or the tugging on the harness when installed the gauge pod and console.

I will try and fix the circuit then take readings again before shelling out $100 for a new unit.

thanks for all the input.
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post #13 of 18 (permalink) Old Dec 16th, 14, 09:23 AM Thread Starter
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Re: Oil Pressure Gauge - Full Sweep Electrical Power Up

I dislike this iphone app -- no edit feature -- I want to correct this "So I test the purple wire and get 4v which explains the high reading..."

to

"So I test the purple wire and get 4v which WOULD explain the high reading IF I back probe test the purple wire at the gauge end and ALSO get a 4v reading."
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post #14 of 18 (permalink) Old Dec 16th, 14, 07:54 PM Thread Starter
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Re: Oil Pressure Gauge - Full Sweep Electrical Power Up

Well after verifying continuity between fuse block and ending unit -- and continuity between fuse block and gauge; I pulled apart fuse block and made sure all the terminals were as far in the fuse block as they could go. bolted it back together and my gauge stopped pegging. I then back probed gauge and get a .5v reading. It looks like it was a loose terminal at the block. I fell kinda stupid about it but at least it saved me from ordering another $100 sending unit.
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post #15 of 18 (permalink) Old Dec 17th, 14, 03:19 AM
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Re: Oil Pressure Gauge - Full Sweep Electrical Power Up

Good to read you fixed it.
No reason to feel stupid - experience is the best teacher.
Don't ever stop learning, but, think the path out before executing.
Common sense prevails.

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