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95 Oil pressure gauge Inoperative

26K views 10 replies 8 participants last post by  broncofocused 
#1 ·
The only problem I have with my truck is the oil pressure gauge... Anyone ever make an attempt at fixing theirs? If so any details would be greatly appreciated. Thanks.
 
#2 ·
whats the problem exactly? not showin pressure at all? or just low?

new pressure switch fromthe parts store is $8-10 and it is located above and forward of the oil filter. single wire connected.
 
#5 ·
yo,
Some background on this so-called "Gauge"; da Sender is just a switch and the gauge indicated whether there is OIL PSI or not.

From the 1996 F-150, F-250, F-350, Bronco, F-Super Duty Motorhome Chassis Workshop Manual:
Oil Pressure Gauge
The oil pressure gauge is a magnetic movement design consisting of a bobbin/coil assembly, a return to zero magnet and a primary magnet. The shaft and pointer are connected to the primary magnet. The bobbin/coil assembly is pressed into a metal housing which has two holes for dial mounting.
The gauge operates through a pressure activated switch. When the engine is started engine oil pressure closes the switch, providing a ground circuit for the gauge coil. Current flow through the gauge coil to ground causes the primary magnet and pointer to rotate, providing an oil pressure reading on the dial face.
The oil pressure gauge does not require adjustment, calibration or maintenance. Also, never remove the pointer indicator from its shaft.
Oil Pressure Switch
The oil pressure switch controls the magnetic oil pressure gauge's pointer position. The oil pressure switch closes under normal engine operating conditions (oil pressure above 42 kPa [6 lb/sq in]). The oil pressure switch opens with the engine (6007) off and no oil pressure.

Oil Pressure Sender
Check gauge operation as follows:
With the key in RUN and the engine off, disconnect wiring connector at the switch. The gauge should indicate on the LOW graduation or below.
Connect the wiring connector to the engine block ground. The gauge should indicate just slightly above mid-scale.
If the oil pressure gauge tests within calibration, replace oil pressure switch.
If the gauge still tests out of calibration, replace oil pressure gauge.

===============


Oil Pressure Mod to Actual PSI "...short R in PCB..." info & NAPA Sender, etc.
Source: by Steve83 (Steve, That dirty old truck) at http://www.supermotors.net/vehicles/registry/media/281470

Oil Pressure Mod to Actual PSI "...short R in PCB..."; "...So someone told me that my 92-96 F-series Oil Pressure gauge really isn't a gauge, it's more of and idiot indicator, this bothered me...:mad: So I decided to test the theory and of course they were right, wether it has 20#'s of pressure or 60#'s of pressure it stays in the exact same spot on the gauge. I tested the sending unit and it is a ON/OFF to ground switch. So I remembered that my old Fox body Mustang had a real working gauge so I found one of those big bulky sending units and the extension and installed it instead. Then it read really low on the gauge while idling.:headscratch: I looked at the EVTM and saw that there is a 20 Ohm resistor inline on the circuit. I pulled the cluster and sure enough there is a resistor smack dab on the cluster paper behind the oil psi gauge. I removed it and the gauge went dead. I soldered a jumper piece inline and POOF. See the pictures and video below..."
Source: by drvovru at http://fullsizebronco.com/forum/showthread.php?t=183293


Installation, Oil Pressure, Water Temp & Transmission Temp., Auto Meter Night Vision in a 95
Source: by Ian L (stangmata, stangmata50l, Bronco) at http://www.fullsizebronco.com/forum/showthread.php?t=100540


MORE INFO LINKs in my site @ http://www.broncolinks.com/index.php?index=949
other gauge info incl Instrument Cluster Removal @ http://www.broncolinks.com/index.php?index=429
 
#7 ·
I've done the switch swap and it's VERY easy. You will need a small peice of plumbing to use as an extension to move the switch away from the block. The new switch is bigger around and longer, so it wont fit where the old one is. All you need is just a small peice of threaded pipe to move it away from the block a few inches or so, lemme see if I can find a pic.

Steve83's link above has more in depth information. here's a pic from his site:
 
#8 ·
Yep, its likely just the switch.

Little tip...there is a special "sensor socket" that makes replacing that sensor a lot easier. Its not too bad, but just in an akward place.
 
#9 ·
Just to clear up the "oil pressure switch" wording that I often see tossed about on this forum;
Vehicles with an idiot light do indeed use an off-on "switch". The OP sender for vehicles equiped with a guage however, use a variable resistor which causes a variance in current flow, which in turn, is reflected at the OP guage (which is actualy just a current meter that reads as "oil pressure"). Both types are often refered to as "sending units" and both types often look alike from the outside. The large, bell shaped sending unit which is pictured in an above post is fully interchangabe with the smaller type that is most often seen on FSBs and Ford cars/trucks which have a guage. One is just as accurate as the other and I've often replaced the "bell type" with the much smaller version.
Just as a point of referance, the factory guage with it's small sender on my 351W equiped '89 model reads between the "M" and "A" upon start up and drops to the "R" position after being driven a few miles. On a very hot day, it will drop to the "O" postion....all clear indications that the guage is indeed reading pressure. I've also found that on most aplications, simply removing the oil filter gives plenty of access for replacing the small-type sending unit but that may not be case with all models or with all engines.

Some things to be aware before modifying a stock Ford sender system;
The bell-type sender is much larger/heavier than the newer-type guage sender. On SB Fords, it was nessesary that the bell sender be mounted by using various lengths of pipe so's it could extend from whatever confines the engine ass'y package had at the time. Without exception, Ford used a hex-shapped aluminum "pipe" for this. I've seen home made extensions made of brass or cast pipe break clean off of engines due to the weight of the assembly causing failure at the threads on the engine-end. What I'm getting at here is that if such an extension is nessesary, me thinks that a high grade of pipe should be used. Some hardware stores carry "high pressure" pipe and fittings which being made from steel, are much stronger than cast iron or brass. If your's don't, your local plumber may have them in the 1/4-NPT size that you'll need.
Modern electrical gauges are far more accurate than most folks think. Most of the problems that one experiences with them are most usualy a defective sender, a bad (or dirty) connection at the sender, gauge or instrument cluster, a broken wire, broken strands within a wire, a frayed wire which becomes grounded, or a break inside the molded connector at the sender. In all my years of wrenching on vehicles, I've only seen one bad guage. All that said, none of these potential problems are hard to trouble shoot. About all you need is a long jumper lead and a test light......sure beats guessing and throwing parts at it.

Hope something here helps.

DGW
 
#10 ·
The smaller version is indeed a switch, once the engine hits roughly 6 psi, the switch opens completely, This is why there is a resistor that needs to be removed when you swap out the sending units. The smaller one is literally an on\off scenario, no variable resistance at ALL. The resistor on the back of the gauge cluster keeps the gauge from going all the way to the other side of the gauge when the switch is turned on. The links in the post above explain it fully.

It is very definate that they are NOT the same, the small one is nothing but an idiot light. Ford just put it on a gauge so it would look functional.
 
#11 ·
Just fixed my oil pressure gauge thanks to this thread!

My oil pressure gauge had been working but intermittently would drop to below normal. Finally it became stuck down low.

Ended up being a corroded connection at the sending unit. Used a wire brush to clean up the inside of the connector boot and the threaded post on the sending unit. Gauge is reading back in the mid "normal" range so all is well again!

Thanks to all prior posters for helping me figure this out!
 
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