Oil pressure sensor wiring on 3800 SC (Page 3/3) Trinten AUG 23, 10:58 PM quote Originally posted by Jncomutt: C8020 appears to be a switch, not a sending unit for a guage. That one closes at 9 PSI. Near zero ohms (which is same as shorted like he has) pegs the guage, makes sense he sees that. High resistance (90-100ohm) would put the guage around zero and cause light to come on. Thank you! And yes. It's frustrating how "switch" and "sender" are interchangeably used for this part across various retailers. Also my apologies to everyone, I keep forgetting PFF doesn't auto-sign you up for reply notifications when you post (or, if it's an option for it to always do that, I don't have it turned on). We did get the '88 sender after some more Searching here on PFF. For those who may need it, the GM Part number is GM1808A, alternative: SMP PS262 (This is the one we got for his car a month or so ago, and put into my car today). and SMP PS245 These are the 3 pin "skinnier" ones. Source for part numbers: our good friends at Rock Auto.