Oil Pressure Sending Unit Conversion

[A robs 23]

1986 Chevrolet K20 - 350sbc - TH400


I am rebuilding my gauge cluster. Switching from the dummy lights to the electrical gauges.

I have the proper oil pressure sending unit. It takes a spade clip. The old sending unit had a clip with three wires. One of those wires connects the oil sending unit to the coolant temp sensor.

How do I rewire this to work?


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[A robs 23]

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[VileZambonie]

You have pictured an oil pressure switch, for the choke heater and dash light. For the gauges you need the oil pressure sending unit and signal wire. Refer to the diagrams and pinouts.

http://forum.73-87chevytrucks.com/smforum/index.php?topic=31456.0

http://forum.73-87chevytrucks.com/smforum/index.php?topic=30115.0

[A robs 23]

My new sending unit




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[A robs 23]

I used my multimeter and found out that the orange-white wire on my old plug is the wire that traces back to my wiring harness under my dash. The green wire runs to the coolant temp sensor. What would the middle blue wire be for?

Am I correct to terminate a spade end onto my orange white wire and connect to my new sending unit?


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[bd]

Did you pay any attention to VileZambonie's post?  That three-wire connector in the image you posted is part of the factory electric choke circuit.  What you presently perceive as an "orange-white" wire was pink-white before age, heat and oil intervened.  The "green" wire began life as light blue.  The dark blue has faired a little better and at least hints at its original color.  The pink/white wire represents ignition power from the CHOKE fuse.  The dark blue wire connects to the instrument cluster CHOKE light.  The light blue wire should connect to the electric choke heater on the passenger side of the carburetor (assuming it remains intact), not the coolant temperature sender.  You can verify all of this using a test light.

The factory wire color for the oil pressure sender/switch is (or was) tan and connected as a solitary wire to the oil pressure switch.  Look for it dangling in the general area surrounding the engine oil filter.

The answer to your original question, "How do I rewire this to work?" is actually illustrated on page 10 in the 1986 Factory Wiring Manual.  If you need assistance interpreting the wiring diagrams, let us know.

[A robs 23]

Bd.

I am converting to gauges. I have my oil pressure sending unit as well, but did not think you all needed to see a picture of it in my hand.

Thank you for the detailed information after the fact.

I purchased the tach conversion kit and am trying to find the gauge feeder wire that will work with my wiring harness/printed circuit.



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[A robs 23]

I have gotten my new oil pressure sending unit installed with the appropriate plug attached.

I compared my “dummy light” printed circuit wiring harness to the pinout diagram that was graciously provided.

The pictures posted is my current pinout. I have not changed anything.

Question:

My current pinout does not seem to match the pinout diagram provided. Why would this be? Aftermarket harness?

IE. In position 16, I have a yellow wire. The pinout shows I should have pink/white.


“Page 10” of that manual definitely confuses me. Is that the manual that I need to use instead?


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[A robs 23]

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[bd]

The 1986 non-guage IP harness connector is boxed in red (image).  The connector is illustrated from the pin side (business end that engages the cluster).  Look closely.  The existing connector that you imaged matches exactly the schematic.  Assuming the new PCB configuration you have matches the factory "with gauges" cluster for 1986, repin according to the alternate (with gauges) IP harness connector illustrated on the schematic.  Otherwise, you will have to map out the new PCB and repin accordingly.  Take your time and be patient.

[A robs 23]

Thank you very much!

I will take my first attempt at a repin and make sure to label every wire prior to disassembly.

This forum is EXTREMELY helpful.


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[bd]

Use a terminal tool like this to depress the locking tab on the back of the terminals and remove them from the connector without damage...

[A robs 23]

Thanks!

I found some success with a tiny little flat head screwdriver. Small small.

Now I need to study and learn how to read those circuit diagrams.

Ill report back when the wiring is done!


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[A robs 23]

I have spent time going over the wiring diagram.

1. Circuit 39 (pink/black) and circuit 150(black) need to be “spliced”.
Does this mean I need the terminal ends and crimp tool?

Circuit 39 leads to a carb fuel solenoid. Do I need to splice this now that I have a manual choke?
I recently converted to a manual choke on my fresh 350sbc rebuild. Switched from electric edelbrock to a manual 600cfm holley.

I have included pictures of how I plan on changing my pin configuration.



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[bd]

I have spent time going over the wiring diagram.

Circuit 39 (pink/black) and circuit 150 (black) need to be “spliced”.
Does this mean I need the terminal ends and crimp tool?

Circuit 39 leads to a carb fuel solenoid. Do I need to splice this now that I have a manual choke?
I recently converted to a manual choke on my fresh 350sbc rebuild. Switched from electric edelbrock to a manual 600cfm holley.

"Splice" means to permanently connect two or more conductors together at a common point.  There are various methods of splicing wires.  Generally, I use suitably sized, non-insulated, brazed barrel, butt or parallel splices that are firmly crimped using an appropriate dimple broach tool, soldered with 60/40 rosin core, and then weather-sealed with marine grade heat shrink. 

There are many crimpers available for purchase at a broad range of prices, some limited to specific applications.  Don't skimp on the crimp!  A good pair of wire crimpers are a pleasure to use.  With the exception of production-grade crimpers that are grossly overpriced, you get what you pay for as far as the precision of broach and durability of the tool are concerned.  High rigidity of the crimper frame is important to achieve predictable, high-quality repeatability over the life of the tool.

Open barrel terminals are best crimped using "D" broach dies.  Non-insulated, brazed barrel terminals fare better with dimple broach dies.  Insulated terminals are best crimped using flat broach dies.

To be clear, ckt 39 (pnk/blk) is ignition feed; ckt 150 (blk) is ground.  The two should never be spliced together!  Any circuits that won't be used, now or in the future, can be deleted.