#1  
Old 07-21-2020, 11:43 AM
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Default Next two issues 70 T/A

Home stretch on resto of 70 T/A. Next issues: Oil pressure gauge not working. Sending unit is new and wire harness is new. I installed a mechanical gauge to oil filter housing port and PSI is perfect. Is there a way to test gauge as I did not not think they really went bad. #2, Volt meter not working (Gas gauge does) Is there a way to test this gauge too? Thanks.

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Old 07-21-2020, 12:27 PM
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The oil gauge should read zero when key is on, engine is off.
If that is OK, unplug blue wire at the sending unit. The gauge should read full pressure. (I think on this one, at least way up)


The voltmeter should have 12 volts to it, if it does, the ground wire/fitting may not be grounded?



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Old 07-24-2020, 05:52 PM
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Default Up date on Oil Sending unit.

Conducted tests as follows:

Motor not running:

Key off: Gauge pegged past high.
Key on: Gauge at "0"

Wire at sending unit unplugged, key on= Pegged past high
Wire at sending unit unplugged and grounded; gauge reads "0"

Motor running= gauge pegged past high all the time.

Interpretation please?

Thanks.

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Old 07-26-2020, 07:51 AM
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Default Results direction please

Can someone interpret these results for me for my next move? Thanks.

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Old 07-26-2020, 09:04 AM
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Not for sure, but I'd say the sending unit is wrong or not working correctly.
Seems to be acting like a non-gauge unit? (either on or off with amount of pressure)

Is the sending unit an aftermarket unit?
Is it a big unit?



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Old 07-26-2020, 12:18 PM
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Got it at Oreilly Auto for about $20 and it is bigger than the original unit I had.

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Old 07-27-2020, 11:33 AM
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The oil pressure sending unit is the shape of a birdcage with a single terminal coming out of the top of the unit.

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Old 07-27-2020, 04:22 PM
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sounds like you have wrong sending unit... The gauge works off of ground. let me explain... the gauge in the dash has no voltage (+12v) till the key is on....the ground is always there coming from the sending unit but it varies depending on how much signal the sending unit is letting thru.
so the sending unit is letting no ground signal thru. thus the gauge doesn't know what to do so it pegs out.
If you could put a dial resister from ground to the wire at the sending unit then you could vary the resistance to the gauge and watch the gauge respond.. So as you varied the ground resistance to the gauge the needle would move.. make sense?
My money is on wrong or bad sending unit.

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Old 07-28-2020, 02:51 AM
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key on: When you ground the wire going to the sender the gauge should make a full deflection to high, like off the gauge. If the gauge is like this without grounding the wire then the sender wire is likely shorted to ground.

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Old 07-28-2020, 10:42 AM
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Thanks for the responses Gentlemen and I guess I will order a new Sending unit and take the other one back. Rock Auto shows 2 for a "gauge"; #1S6563 for $9.20 and a PS155 for $14.85. They dont show one from AC Delco so any opinion on either of these?

Thanks Dave

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Old 07-28-2020, 10:52 AM
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Quote:
Originally Posted by dpoltzer View Post
Thanks for the responses Gentlemen and I guess I will order a new Sending unit and take the other one back. Rock Auto shows 2 for a "gauge"; #1S6563 for $9.20 and a PS155 for $14.85. They dont show one from AC Delco so any opinion on either of these?

Thanks Dave
Dave,

The original blew out on my '73 and was spilling oil due to the high oil pressure. Could not get one locally so I called Ames and got two $28.00 a piece. Part # FM472.

Hope it helps.

Jim

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Old 07-29-2020, 07:16 PM
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Default Great news!

Replaced the P.O.S. Oreilly sending unit with one from Napa and now the oil pressure gauge works perfectly! Thanks guys!! On to the Volt gauge that always reads "0". I jiggled the connector on the back of the volt gauge and the gauge worked, indicating 15 volts for about 5 seconds before it quit. I removed the connector from the volt gauge and took a reading with my Volt meter at the orange lead and I had 12.5 volts with the key in the "on" position. Because there is 12 volts at the orange wire, I presume the gauge is bad? Can I replace just the volt meter with a newer one w/o replacing the "fuel" gauge? I do have another newer unit but I dont want to replace the fuel gauge as it is original to this 1970 and I dont want one that say "Unleaded". Thanks again.

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Old 07-30-2020, 09:44 AM
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Make sure the ground wire on that volt guage IS going to ground.

If it's not grounded good it may have stray voltage on it keeping the guage from working.

Clay

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Old 07-30-2020, 10:37 AM
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Default Ground?

Do you know where the other end of the ground/black wire terminates? Thx QS. Dave

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Old 07-31-2020, 07:46 PM
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Default Bad Volt gauge!

I plugged in my spare volt gauge and it worked properly so the original gauge is defective. Thanks everyone.

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