0-120 Oil Gauge Installation

I recently purchased a new 0-120 oil pressure gauge and sender unit. I am replacing 0-60 and there are two rubber connectors on the real housing; the one on the left is smooth and the one on the right has ribs. Problem is the new gauge has the riibs on the left and is smooth on the right. Do I just connect the wire connected to the ribbed connector to the ribbed on the new gauge or flip them?

Ribbed connector

The ribs on either the connector or the gauge according to the Military Specification for these items denotes the the positive voltage connection for both items.

Be sure you get it right, if you hook it up wrong your oil pressure will be negative. ....bearings sucked full of air and your oil pump blowing bubbles in the pan...

Oh my, what do I do!!!!!

why would you want a 120 lb gauge for 60 lb oil pressure?

tom

m-35tom said:

why would you want a 120 lb gauge for 60 lb oil pressure?

tom

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My deuce came straight from surplus with a 120# gauge. Cold start it is around 70~75#, as near as you can tell from the markings on the gauge, and after some driving it will drop to 40~45 at idle and back up to 55~60 running down the road. Haven't installed a mechanical gauge to verify. Reading didn't change much between running 15W-40 or straight 30W. Just my experience.

My M220 came straight from surplus with a 120# gauge as well. Trouble is the old gasser runs 30 psi under way and it idles at 5 psi as the specifications indicate. It is hard to read 5 psi on a 120# gauge. I am looking to swap gauges the other direction. I heard from a retired MV maintance guy that the senders were different.

Oldfart said:

I heard from a retired MV maintance guy that the senders were different.

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Yes it is a different sender depending which gauge you have. If you switch to a 60# gauge you need to have a 60# sender.

On both the 0-60 PSI and the 0-120 PSI gauges, the ribbed connector MS33800 Style 2 should be connected to the SENDER (Oil Pressure Transmitter). The smooth connector MS33800 Style 1 should be connected to the IGNITION (24 Volts DC when the ignition is on). If you hook the gauge up wrong you would just drive the needle on the gauge in the wrong direction (possibly hurting the gauge), but you would not affect the actual engine oil pressure in any way whatsoever.

Interestingly, the parts technical manual TM9-2320-361-20P lists the following for the Oil Pressure transmitter and indicator.

Figure 54, Item No 12, Transmitter, Pressure - 24 Volt DC 120 PSI.
Part No MS24539-1 (see Mil-Spec MS24539), 0-120 PSI when connected to indicator MS24540.

Figure 46, Item No 32, Indicator, Pressure, 24 Volt DC, range 0-60 PSI.
Part No MS24541-2 (MS24541-1 cancelled; see Mil-Spec MS24541).

So the parts manual lists a 0-120 PSI Transmitter with a 0-60 Indicator.?.?.?

The Transmitter Mil-Spec MS24539 says 0-120 PSI when used with Indicator MS24540.
Part No MS24540-2 (MS24540-1 cancelled) is an Indicator, Pressure, 24 Volt DC, Range 0-120 PSI.
Calibration data for all 3 items is attached as a Word file.

From the attached calibration data an MS24541-2 indicator 0-60 PSI would function but it would indicate half the actual oil pressure PSI if used with the MS24539-1 transmitter 0-120 PSI. The gauge wouldn't be hurt but the reading would be off. The correct combination for a 0-120 PSI Oil Pressure reading is an MS24539-1 transmitter 0-120 PSI with an MS24540-2 indicator 0-120 PSI.

PS the two cancelled indicator part numbers MS24540-1 and MS24541-1 had luminuous dials (possibly radioactive).

Also attached are the transmitter and indicator MIL-SPEC's.

1-60 PSI Tramsitter

The 0-60 PSI Transmitter is MS24538-1 (MIL-SPEC MS2453 Transmitter, Pressure, 24 Volt DC 60 PSI.
MS24538 attached.

pjvargas said:

So the parts manual lists a 0-120 PSI Transmitter with a 0-60 Indicator.?.?.?

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I've owned two deuce and a half's in my life, they were both set up this way. (I was aware of this going in, so no big deal...) Oil pressure for these trucks is all over the map, and "typical" is way more than double the "minimum". Parts are available for both, BUT... If you just always replace the sender's with the 120 pound version, That means most trucks will be an inaccurate reading, but all will still be "in spec" and not a cause for corrective action, and any error is on the side of caution. Sounds fine from a bean counter's chair....

At least that's my guess on it anyhow....

Oil Pressure range

TM 9-2320-209-10-1 lists the startup oil pressure is 30 to 40 PSI.
TM 9-2320-361-10 Section 2-4 says the normal oil pressure range is 10 to 75 PSI.
Looks like the safe play is to have the 0-120 PSI transmitter and gauge rather than the 0-60 PSI setup.