I have a 2002 Ranger 2WD with a 3.0 liter in it. Bought it new and have had this problem since day one. After driving at highway speeds for 15-20 minutes when you come back down to idle speed, the oil pressure gauge chatters and the needle flickers back and forth like it is going to jump off the gauge. Ford dealer replaced the sending unit once and it worked ok for a week or two and then the problem returned. At about 75,000 miles the needle jumped so much that it jumped over the stop pin on the gauge and now comes to rest on the underside of the stop pin. So now the needle can’t chatter anymore but just rises to the underside of the stop pin and stops there when the engine is running. The gauge still makes a grumbling noise and I now have 130,000 miles so I guess everything is ok except for the strange oil pressure grumbling noise. Anyone else had this problem or care to comment on a cause.

 

I don't have the problem, but will comment anyway. FoMoCo puts a voltage regulator on the backside of the instrument cluster. Well, they did in the past. I was a little box with two connections that snapped onto the printed circuit, much like a 9-volt battery connector. This mechanism regulates the nominal '12 volts' that the system produces down to a lower voltage for the instruments (coolant temp, oil pressure and fuel) to use. This adjusted voltage is more stable than the battery voltage, so you get more stable readings on the gauges. The alternator puts our ~14 volts, the starter draws a lot of amps, lowering the voltage, so the instruments have a range of voltages that would make their readings wander.
This little box may be failing on your machine, and letting through the 'battery' voltage rather than the regulated voltage the gauge likes to see. Your dealer should have checked this when the vehicle was new. They are pretty cheap... but you have to take the cluster out. The old versions actually vibrated, and more or less 'chopped' the available voltage down by making it unavailable for bits of time, so the 'average' was some number less than battery voltage (~8volts?? .. it's been a while).
The sending unit on most vehicles with a gauge for oil pressure was just a binary on/off switch that closed at 5psi oil pressure. Ford put a resistor on the instrument cluster printed circuit that would put the oil pressure right in the middle of its travel when the switch closed(oil pressure got to 5psi minimum). Unless you have a 'domed' sending unit, in which case the gauge would be a lot closer to reality.
Anyway, I bet the regulator is not regulating. You can take the cluster apart and using a non-finger probe, move the around the stop so it can do normal movement.
tom

 

Thanks for the reply. I always felt back in 02 and 03 when the truck was new that the Ford dealer just replaced the easiest thing to replace which would have been the oil sending unit. Since it seemed like a minor annoyance I never went through the hassle of having them actually fix something correct. Someday I will probably take it apart and at least put the needle back between the banking pins where it belongs although it will probably jump back out again when it starts fluttering.

 

Where Do I getn this Instrument cluster Voltage Regulator/resistor? I checked Rockautoparts.com &Autozone on web.Dealer item?Only?

 

I saw this highlighted in another post as an "IVR"? Is this and Where?,can I get one before I take the Panel out?

 

Sorry rangerte I have no clue where to get this voltage regulator, hopefully tomw will be able to answer your question.

 

Appreciate "El Respondo Rapido!" I been lookin ALL over even typed Google 2002 Ranger Instrument cluster voltage regulator!Got 6000 hits! But No answers.Rockauto.com&Autozone,NOT!But on Google sidebar they mention it,I think? Unless they're referring to the Charging system regulator?I'min No hurry,as this has been going on for ,I don't know How long? I just noticed it was occuring more frequently! Wanna get On this,I'll NEVER get a New vehicle on Social Security!Waaaaaaaaa!!!But thanks ,I'll check back and call around too.I'm PC "burnt out!"

 

I had the exact same problem with my 2002, 3 liter when I switched to mobil 1 it stopped though I don,t think that the oil had any thing to do with it . Ifyou have gone that many miles it's just a indication problem.

 

"MYSTERY" of the IVR(Instrument cluster Voltage Regulator,apparently :SOLVED!I called my local Ford dealer where I bought my Ranger.The Parts Tech. was Very knowledgeable about the above mentioned"Oil Pressure gauge 'needle flicker";Replace IVR!According to one of our Posters who mentioned that they "Used to" have one on the instrument cluster!They now are "built in" the Gauges:Oil,Gas,&Temp.Thank you ,Jeremy,Heller Ford,Escondido,CA.!No wonder I couldn't find the IVR?Gotta buy ther gauge!Thank you folks who mentioed that I replace BOTH switch/sender&GAUGE!

 

TOMW! Knew they "used" to have an IVR on the Gauges! Thanks Tomw!Because of your knowledge,it concurred with Ford dealer Parts!"New" gauge has it "built in"!$80 for Oil gauge(black),I'll price around after changing the $10 PITA Oil sending unit!

 

Well, rangerte, us old f*rts have to hang together,... or we'll all hang separately. Heh. Give me a couple -three years for the SocSec thing. Taking apart the dash isn't so bad, but it will feel that way when you pull on something that was a snap-together install. Seems as if stuff will break. The speedometer cable was a snap fitting for installation, and a very difficult to describe 'push' to get apart when you are reaching up under all the wires and such. Not sure what you have, but you have to more or less bend the cable end to get a plastic hook out of the groove in the speedo head. Once you see it, it makes perfect sense, but sure is a tussle doing it blind. If you could remove the dash 'trim' panel, you may be able to remove the clear plastic with about 4 screws, and wiggle the pointer past the stop. Turn the key, run the engine, and see what it does. If you end up removing the instrument cluster, you may be able to see a loose connection on the gauge after you remove it. Could save a few dollars.
tom

 

Thanks to all &TOMW!I learned more about Oil pressure gauges,senders/instrument clusters,etc.,Then in My WHOLE Life!I took Auto shop in HS,64-68& have done almost ALL my own work.Here I learn even more then ALL the classes ,I could EVER take.With You guys experiences and web info plus books.I GOT it! Thank you ,I will change my Pressure switch sender(Since I got it)TEN Four!