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Old 04-04-2011
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Oil Gauge/Pressure Switch Questions

Started up my truck and my oil gauge started having a seizure and spinning around then finally hung behind the peg and is stuck there. I know that this gauge is in fact a dummy gauge. But ever since that happened my truck will not keep oil in it. I got up under it and looked and it seems to be leaking oil right around where the filter is. So if your laying on the ground facing up it would be the left side of the motor. Ive been told it could be a bad sending unit? But when I look for the part the only ones they have are for the light and not the gauge. ButI've seen some that say light/gauge like they work for both. Any info would be appreciated. Thanks.
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Old 04-05-2011
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The sender is only a switch that triggers at about 7 psi , so they are the same.
Remove the oil filter and check the filter mount for an old gasket that got stuck on there from a previous oil change.
Also sounds like you need a new oil gauge.
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Old 04-05-2011
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Quote:
Originally Posted by OTRtech View Post
The sender is only a switch that triggers at about 7 psi , so they are the same.
Remove the oil filter and check the filter mount for an old gasket that got stuck on there from a previous oil change.
Also sounds like you need a new oil gauge.
The sending unit "switch" for a light, and the gauge are not the same. The sending unit for the light is a "normally closed" switch that OPENS with about 7 PSI of oil pressure, the sending unit for the gauge is a "normally open" switch that CLOSES with about 7 PSI of oil pressure.
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Old 04-05-2011
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Thanks Bob . I'll keep that in mind next time.
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Old 04-05-2011
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Over the years, there have been several iterations in how the gauge and/or light have been controlled.


2004~2011: Light only
  • Normally closed oil pressure switch
  • Switch closes with oil pressure below trigger value.
  • Low oil pressure indicator LED only. No oil pressure gauge
  • Oil pressure sending switch provides ground directly to the low oil pressure LED in the cluster when pressure falls below the trigger point.
2001~2003: Gauge and light
  • Normally open oil pressure switch
  • Switch closes with oil pressure above trigger value.
  • "Dummy" oil pressure gauge reads either zero or ~40% full scale at battery voltage
  • Oil pressure switch grounds gauge winding for 40% indication and also sends ground signal to Anti-Slosh Module which in turn controls ground for "Check Gage" Light in cluster.
  • Check Gage Light illuminates for low oil pressure but also for low fuel level or high coolant temp.
1996~2000: Gauge and light (optional)
  • Normally open oil pressure switch
  • Switch closes with oil pressure above trigger value.
  • "Dummy" oil pressure gauge reads either zero or ~40% full scale at battery voltage.
  • Oil pressure switch grounds gauge winding for 40% indication and also sends ground signal to Anti-Slosh Module which in turn controls ground for "Check Gage" Light in cluster.
  • If equipped, Check Gage Light illuminates for low oil pressure but also for low fuel level or high coolant temperature. Base clusters WITHOUT tachometer used in 96~2000 Rangers may not have the Check Gage Light feature.
198?~1995: Gauge Only
  • Normally open oil pressure switch
  • Switch closes with oil pressure above trigger value.
  • Real oil pressure gauge.
  • Oil pressure switch grounds a 20-ohm resistor in series with the gauge winding creating a 40~50% indication. Effectively converts real gauge into a 2-position dummy gauge in operation.
  • These years can be modded to give analog indication by jumping the resistor and substituting a variable resistance sending unit from prior years.
.
Mid eighties: Gauge Only
  • Conventional oil pressure sending unit provides variable resistance to ground.
  • Real gauge gives analog indication of oil pressure.
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Old 04-05-2011
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Quote:
Originally Posted by rwenzing View Post
Over the years, there have been several iterations in how the gauge and/or light have been controlled.


2004~2011: Light only
  • Normally closed oil pressure switch
  • Switch closes with oil pressure below trigger value.
  • Low oil pressure indicator LED only. No oil pressure gauge
  • Oil pressure sending switch provides ground directly to the low oil pressure LED in the cluster when pressure falls below the trigger point.
2001~2003: Gauge and light
  • Normally open oil pressure switch
  • Switch closes with oil pressure above trigger value.
  • "Dummy" oil pressure gauge reads either zero or ~40% full scale at battery voltage
  • Oil pressure switch grounds gauge winding for 40% indication and also sends ground signal to Anti-Slosh Module which in turn controls ground for "Check Gage" Light in cluster.
  • Check Gage Light illuminates for low oil pressure but also for low fuel level or high coolant temp.
1996~2000: Gauge and light (optional)
  • Normally open oil pressure switch
  • Switch closes with oil pressure above trigger value.
  • "Dummy" oil pressure gauge reads either zero or ~40% full scale at battery voltage.
  • Oil pressure switch grounds gauge winding for 40% indication and also sends ground signal to Anti-Slosh Module which in turn controls ground for "Check Gage" Light in cluster.
  • If equipped, Check Gage Light illuminates for low oil pressure but also for low fuel level or high coolant temperature. Base clusters WITHOUT tachometer used in 96~2000 Rangers may not have the Check Gage Light feature.
198?~1995: Gauge Only
  • Normally open oil pressure switch
  • Switch closes with oil pressure above trigger value.
  • Real oil pressure gauge.
  • Oil pressure switch grounds a 20-ohm resistor in series with the gauge winding creating a 40~50% indication. Effectively converts real gauge into a 2-position dummy gauge in operation.
  • These years can be modded to give analog indication by jumping the resistor and substituting a variable resistance sending unit from prior years.
.
Mid eighties: Gauge Only
  • Conventional oil pressure sending unit provides variable resistance to ground.
  • Real gauge gives analog indication of oil pressure.
Nice job Bob, thanks!!
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Old 04-05-2011
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So I guess not being rude I really appreciate all your answers but that still doesnt answer my question? Is it the sending unit or not? Or could it be that an old oil gasket was left behind? Thanks.
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Old 04-05-2011
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Assuming that you have a 2003, there is a sending switch, not a sending unit.

The sending switch cannot make the gauge go any higher than about 40% of fullscale with normal battery voltage. The sending switch also cannot cause the oil leak at/near the filter.

A double gasket could cause the oil leak but could not cause the gauge problem.
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Old 04-06-2011
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Turns out after last night the one time I didn't change my oil myself because I didn't have time the jiffy lube people didn't screw my oil filter on tight. What the ****. I got up under it and took it off by barely applying any pressure. I was livid but I guess that's what I get. But my gauge is still messed up. I'm starting tothink it may be something electrical screwed up in the cluster.
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Old 04-06-2011
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Dummy gauge huh? Now I know why it just shoots up to a point and stays there. Good to know its not a full range meter.
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