Oil Pressure Gauge Not Working On 3800 Swap (Page 2/2) Crazy_ones24 FEB 23, 12:57 AM quote Originally posted by olejoedad: Where are the wires from the two wire sender terminated? The gage supplies 12VDC to the sending unit, the sending unit puts a variable resistance on the gage lead on its way to ground. The resistance is what makes the gage needle deflect. Black wire, no clue. Read 44 ohms of resistance. As does one of the grounds (need to fix) in the engine bay (not the main ground). Tan goes to E C203 like it's supposed to. My car isn't at my house and I can only work on it on the weekends for the most part so I can't answer some specific questions quickly. I've ordered an 88 sender and plug which should be here tomorrow so hopefully I can get that all wired up over the weekend. Crazy_ones24 FEB 23, 12:58 AM quote Originally posted by theogre: [QUOTE]Originally posted by Crazy_ones24: I verified that the gauge is good by applying power to the wire that runs into E C203, the gauge moved to 0. The sender being good evidently doesn't matter because it's the wrong OPS for the job. Means gauge sees 0 ok & is very easy... Check gauge w/ resisters tell you wiring etc reads right. Resistor & Sender max Ω moves gauge 80psi. higher then other wiring or sender has problems. OE 85 dash had a Light & Switch for oil pressure w/ Solid Tan wire at switch/sender & ground thru threads to the block. 87 Dash expect same wiring w/ 0-90Ω sender. OP switch/sender Also have 2 others running power to F-pump. All thru C203. Old and 88 OPS socket only have 3 wires. Some aftermarket 88 plugs has 4 wires, 4th goes nowhere. See cave sender page. OE OP F-pump switch is Parallel w/ F-pump Relay. You have to find out what mess the swap did to run F-pump before finding out what is wrong w/ wiring the OP sender for that.[/QUOTE] Got it. Thanks. I'll try to get it all wired up over the weekend and let you guys know if I have any more issues. olejoedad FEB 23, 06:28 AM The black wire can be cut and capped and left in place. The tan wire can be used to run the gage with the 88 sender, it should be on 'A' on the sender plug. 'B' and 'C' are not required to be hooked up for the car to run or the gage to work, they are simply a backup power circuit to the fuel pump in case the fuel pump relay fails. The two wire OPS isn't set up to run the gage, or provide a back up power circuit.