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Swinging oil preasure guage

steelynirvana

Member
Joined
March 16, 2014
Messages
27
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City, State
North Carolina
Year, Model & Trim Level
1993 Explorer
So this morning after driving 15 or so miles between 70-85 [in my 93 XLT 5 speed] on the interstate I get off the exit and im waiting on the light to change. I hear a tapping noise that Ive never heard before, look down and see my oil preasure guage is rapidly swinging back and fourth from L to H. I mean like 3 complete swings a second. I didnt hear any death ticking or rattling so i continued the last 2 miles to work and couldn't get it to duplicate this afternoon. Im thinking the sensor is shot but something is telling me the pump could have been sucking air too but it wasn't low on oil

Anyone else had this problem before?
 



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From what I've read, that gauge is a dumb gauge. It's either on or off, meaning that it either shows pressure or it doesn't. It won't show low or high pressure, it will just show pressure.

Based on that, I'm not sure why the gauge would swing. I've noticed mine moves occasionally and has a different level every other time the engine runs. I think it's just a crappy gauge.

If I were you, I would get a true mechanical gauge on it, run it into the cab and keep an eye on it. Read what the actual PSI is and see if it drops into a dangerously low amount. If not then maybe go for the sending unit? Or just buy a permanent and more accurate gauge?
 






That gauge is a dampened gauge which means it is not supposed to move quickly no matter what the input is. It sounds like your gauge cluster is either damaged or has been modified previously (see the oil pressure gauge mod)
 






Like natenkiki2004 said.. It isn't really a gauge.

The stock sending unit is really a switch. At 5 psi it closes..

That means once you hit 5psi it grounds the wire and the 20 ohm resister behind the cluster makes it read 'around' the middle of the gauge. Once it is in the middle, any movement is just voltage/grounding issues. That is assuming you don't really have oil pressure dropping below 5psi or have some kind of wiring/sending unit/switch issue.

There is a thread in the Useful Thread forum, interior section on how to make the oil pressure gauge read like a real gauge. It is just changing the sending unit to a real sending unit (not a switch) and jumping over the 20 ohm resister on the back of the cluster.. Once you do that the gauge will move with pressure.

If the mean time, you can just put on a mechanical gauge. I have a cheap one that I keep for this. When I need to know what is going on with a vehicle without a true gauge connect the oil pressure gauge line to the engine and zip tie the gauge to the windshield wiper. It looks like crap, but I'm just testing..

~Mark
 






My 2003 ranger tremor 3.0 did this, and it just needed a sensor. Apparently, very common.
 






Revisiting this thread because I replaced the sensor back in August and its been doing fine until this week when it started wildly swinging again. I can give it a little throttle, to around 800-1000rpm and it will stop and stay in the middle. Ive got a feeling this might be some kind of grounding issue, could be coincidence though because of a few other things. 4wd doesn't work but when i press either buttons, stereo speakers pop and crackle (Aftermarket unit but I respliced everything thing they did with butt splices as thry twisted wires and used scotch tape to insulate them, (crazy but headlight switch was done same way:eek:)) , sometimes when the radio is off, random static will be coming from the speakers. I was trying to get rear wiper to come on a few months ago, other day it finally came on from where I left the switch on.

Anything sound familiar to anyway, any suggestions to where I should start? Im suspecting some has been in the instrument panel before as trim was hanging off on one corner when I bought it. Anything back there that could have gotten pinched or even worse, spliced or tapped?
 






Wow, yea, it sounds like someone was just cutting and splicing wires like crazy. That would be tough to figure out without visually inspecting all the harnesses. For the speakers to pop and have static, they're getting power from somewhere and over time that could just burn up the voice coils in them.

I wouldn't worry about your oil sensor now, you definitely have some electrical gremlins running around and I don't envy you. I will say though that since I posted in this thread, I've replaced my oil pressure sender and the dash gauge is rock-solid right in the middle. I don't know if it was a poor contact or if the OEM sensor was just gummed up. I also T'd off the sender port and hooked up a mechanical gauge and when warm, I'm seeing 20-50 PSI (idling in gear to 2500+ RPM).
 






I don't know which part of NC you're in, but I would swing by a pull-a-part and grab another cluster (the whole thing) and swap it in. I bought my cluster when I last lived there (2011) and it has worked great, but I was also looking for a 6 digit odometer from a 94 and I had mileage confirmation via history report.

Enough rambling....

So other than the headlight switch and radio wires, have you noticed any other splices or cuts on the wiring harness itself?

My suggestion and it is a huge pain in the *** but I would swap out body harnesses. It is very in depth because the entire interior needs to come out including the dash. It took me 3 days of steadily working on it to do this. I would go this route if you had issues with power door features.

I see you mentioned 5 speed, 4wd, rear wiper, and I would guess that you have the rear defogger as well. The 4wd electric transfer case is on a separate harness. What other options do you have?

However, you might be able to just replace the dash harness if that is the only place you are having issues, the downside is the heater/ air conditioner cables and vacuum hoses are very delicate and brittle and theses really need to be disconnected in order to get the dash out all the way.

I have broken two a/c heater cables (really the clips that secure the cables to the a/c heater unit itself) and vacuum lines by accident due to the delicacy of these parts.

There's a thread on here of how to remove your dash. I would read on it and try a salvage vehicle before destroying yours first.
 






This is slowly becoming a nightmare fir me, had some free time this afternoon so I started pulling here and there. Popping noise I believe might be coming from some wires on the factory harness that were stripped and left bare. Cig lighter/ashtray harness is spliced, no big deal but I ve got a real pain the the butt im working on now. For some reason they spliced the purple orange that controls the blower, turn signals, rear def, and backup lamps. It got so hot it melted the insulation a good ways. Ive got it cut at the block, trying to trace back, looks like three taps from fuse block. Got a jumper and touched it to one where insulation is showing, makes everything work and unfortunately it appears to run behind the instrument cluster. I can see the bundle but getting to it is gonna be a real pain


I don't know which part of NC you're in, but I would swing by a pull-a-part and grab another cluster (the whole thing) and swap it in. I bought my cluster when I last lived there (2011) and it has worked great, but I was also looking for a 6 digit odometer from a 94 and I had mileage confirmation via history report.

Enough rambling....

So other than the headlight switch and radio wires, have you noticed any other splices or cuts on the wiring harness itself?

My suggestion and it is a huge pain in the *** but I would swap out body harnesses. It is very in depth because the entire interior needs to come out including the dash. It took me 3 days of steadily working on it to do this. I would go this route if you had issues with power door features.

I see you mentioned 5 speed, 4wd, rear wiper, and I would guess that you have the rear defogger as well. The 4wd electric transfer case is on a separate harness. What other options do you have?

However, you might be able to just replace the dash harness if that is the only place you are having issues, the downside is the heater/ air conditioner cables and vacuum hoses are very delicate and brittle and theses really need to be disconnected in order to get the dash out all the way.

I have broken two a/c heater cables (really the clips that secure the cables to the a/c heater unit itself) and vacuum lines by accident due to the delicacy of these parts.

There's a thread on here of how to remove your dash. I would read on it and try a salvage vehicle before destroying yours first.
 






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