A friend has a '93 Bonneville 3.8L.
His Oil Pressure Gauge needle is pinned all the way on high.
Should we be thinking, bad Gauge, or faulty Oil Pressure Sending Unit(OPSU)?
If faulty OPSU, where is it located?

Yes, it could be either. The easiest way to access the sending unit is by taking off the wheel and mudguard. It'* near the oil filter. Do you have access to a service manual?

my sending unit isnt that hard to get. I want to say that just reach hand on the passenger side of the engine near the firewall and follow a wire to the sender unit. it is black and tubular. make sure you have the new one when you pull this one because it has to be a quick switch! good luck and they are only like $20 or so!

mine is doing that too when I first start it up but...after about 50 hwy miles it backs up to a seemingly correct reading.


However, I noticed yesterday that hitting a bump joggled the reading. I started banging on the dash area near the gauge and it fluctuated with each smash. Appears to be a loose wire or connection at the gauge.

I would guess that there are probably no such wires bac there although I havent checked so I am really not sure what I should do...any suggestions?

DA

Yes, since you can thump on the gauge cluster and see the gauge react, you've got a loose connection in there. There'* a TechInfo article on how to remove and reassemble the gauge cluster.

Note that I did say just to _reassemble_; I doubt that anything needs to be replaced, but the pin connectors get oxidized over the years, and a reassembly scrapes them clean again. In the case of your gauge, it'* a 4-pin assembly that plugs into the circuit board, and probably needs to be removed and plugged in again, that'* all.

As for the original poster with the pegged gauge, it might be that the wire to the sender is disconnected (at least intermittently). I can't remember, though, whether the gauge pegs on the Low or the High side when the signal is lost. Trial and error might turn something up there. (If the sending unit is wet with oil on the outside, it'* toast anyway.)