Hello and thanks in advance for any info. I have a 2001 monte carlo ss with a 3.8 "k" motor. I have to replace the oil pressure sending unit because it is pouring out of the pigtail. My question is I have it unplugged and the oil pressure gauge is still working as normal. Its been a long time since I worked on one of these but I don't remember a second sending unit. Can anyone tell me what I am missing? Thanks again.
the oil pressure switch with a LIGHT duralast/ wells "PS152" Normally Closed to Ground, Opens 2.5-5.5 PSI, 1/4"-18 NPTF Dryseal Thread,
with these specifications.. the oil pressure gauge is a SWITCH.. ON or off. when there is no oil pressure it pulls the gauge needs to ZERO.. when the pressure comes up.. the switch opens and the needle rises..
i am suspect of these specs off the wellsweb page.. as the guage type sending units are usually NORMALLY Open and close at 5 or 6 pounds. i think the specs are WRONG but i don't have a part in my hand to ohm. .
the only thing you can do is STOP THE LEAK.. if your 3800 has more than 130,000 miles on it.. you might want to pull the oil filter adapter off the side of the timing cover. after cleaning all the way around the mounting flange with a wire brush and compressed air so there is no chance of contamination falling onto /into an oil passage.. pull the oil pressure relief piston out and then the spring and replace the spring.. i have not found enough of them with broken oil pressure relief valve springs to get any idea of when the springs wear out and start breaking.
some of the later buick 3800 motors use a 10MM oil pressure switch thread.. so a special adapter is needed to manually check the oil pressure.. fairly easy to make..
The info for the cluster comes from the PCM which gets a signal from the OP switch.
Chances are its displaying the last good value that it had read , as it may be able to strategize that the circuit has gone open ( unplugged)
Not a real good thing if you really want to know what is going on down there.
Change the leaky sender, recheck gauge operation.
Thank both you for the info. I wasn't thinking about the switch. It's been a few years. I was going to replace it anyway was just curious why the gauge would come up as if it were plugged in. I appreciate it. Have a good night.
with the normally closed at Zero and Open..above 5.5 Psi.. if the wire is disconnected.. you look like you have PERFECT oil pressure every time..
i wish with gauges that they would put a BULB in a RED lens behind the oil pressure gauge so you would get a clue that the oil pressure has DROPPED below 5 PSI..
i actually had an engineer on the phone from wells one day trying to figure out something.. i ask him about the market for REAL variable resistance sending units for ford and general motors cars.. but i don't have access to one.. so i could hook up an extended harness and a variable resistor.. to see the values it takes to make the gauge move.. the gauges might only really dumb units.. its just something i thought up in a second. i know that earlier models used a resistor in the circuit.. those models used a reversed oil pressure switch.. open with no pressure and closed circuit above 5 psi..
please when you get the new sending unit.. OHM it with no pressure applied.. continuity or no continuity..
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