‘83 K5 350/4wd: aftermarket oil psi switch/sender/choke heater wiring question w/pics and schematic

[BlazerBill]

‘83 K5/350/4wd question: Please confirm my wiring/splicing is correct per the Haynes manual schematic. Tan wire from dash oil/choke indicator through firewall to new factory style oil psi sender (at distributor) spliced into dark blue wire to the oil psi switch and spliced with Lt blue wire to one wire from switch. The other wire from switch (pink/wh stripe) through firewall to fuse block. Basically, I need to know if the Tan (from idiot light to sender) spliced to DK Blue (from switch) and LT Blue (from choke) to DK Blue splices are correct. My understanding: the choke, oil sender and switch are tied together. If the sender doesn’t see oil press, the switch won’t close and won’t allow the choke heater to operate preventing engine start. Is this correct? Thanks, everyone!

 

[EvilGenius]

I think your understanding of that circuit is a little backwards. The reason the choke is wired with the oil pressure sensor is to prevent the choke from opening when the key is left on.

The way it operates is the sensor closes and passes current at a predetermined oil pressure. Something like 5 psi. This allows the choke heater coil to start heating up and gradually opening the choke plate. If your truck gauge cluster is optioned the right way there is an choke alert light that comes on with no oil pressure. When that alert light is off that means the choke is opening and you have oil pressure.

The oil pressure gauge is a completely different circuit and shouldn't have anything to do with the choke wiring. The gauge is wired up to the oil pressure sender.

 

[BlazerBill]

Okay, I understand your explanation and is the way I understood it in my head, thanks. The Haynes manual (see photo) shows the DK Blue wire (from switch) connected to the LT Blue wire (from choke) at the switch and from the switch, the DK Blue wire connected to the Tan wire that goes to the sender and to the oil/choke indicator and press gauge. Isn’t this the same as I wired/spliced as show in my drawing schematic (see photo)? Is this not correct? Or, how should I have done it? Thanks, and sorry for my confusion!

 

[EvilGenius]

Here is a snip of the 1984 wiring diagram from the GM service manual. I can't say what changes there may be from 83 to 84. There seem to be some differences with your Haynes diagram.

It's been a while since I wired this up myself, but my understanding of the pink/white wire (circuit 350) is that is is 12v hot with key on. This feeds one side of the oil pressure switch. The other side has 2 outputs, one to the choke heater and one to the dash indicator light. The tan (circuit 31) wire should run right to the oil pressure gauge. It shouldn't interact with the oil pressure switch circuit at all.

You must be registered for see images attach

 

[BlazerBill]

Okay, along with my other post, I think I understand what you and @EvilGenius are saying. I must have misinterpreted the colored ClassicCarWiring.com diagram that says “Oil PSI SW (6 cyl w/o gauges-see pic) as meaning it was only specific to 6 cylinders (thus this separate post asking what to do with the 931 DK Blue wire). With y’all’s explanation, I now understand that my loose 931 DK Blue wire goes to the switch and is not spliced to the Tan wire that shows in the black and white Haynes manual that indicates that the DK Blue (931) wire is connected to the Tan wire (see pic) which is very misleading. So, all I need to do at this point is to UN-splice my DK Blue 931 wire from the Tan wire (to sender) and connect the DK Blue wire end from the switch to the other loose wire that I thought was specific to 6 cylinder engines. Make total sense now. Thank y’all, so much!

Attachments​

• You must be registered for see images attach
  
  IMG_1546.jpeg
  163 KB · Views: 0
• You must be registered for see images attach
  
  IMG_1545.jpeg
  102.9 KB · Views: 0
• You must be registered for see images attach
  
  IMG_1529.jpeg
  157.6 KB · Views: 0

 

[BlazerBill]

Thank you so much Evil Genius!

 

[EvilGenius]

Thank you so much Evil Genius!

Hey no problem. For whatever reason I find the wiring on these trucks to be pretty straight forward. Glad I could help.