I've got a '72 so have no temp sender originally and am adding one and a gauge. My question = where's the best place for the single (GR/BK) wire to exit the loom from the tunnel (Im trying to mock up changes to my '72 harness). I'm concerned about burning up the wire if it gets too close to exhaust. What about having it exit with the Yellow wire from the relay box to the starter then having it continue and loop under the engine? .. or possibly have it exit under the bottom of the snorkle fitting, and just reach straight across the the temp sender? Thoughts?

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The factory schematic has the answers. You will see that 72 was a transition year for this circuit. 70-71 did not have the circuit at all. 72 had the circuit in the ignition harness, which connects to the main harness at the relay board. There would have been a single wire connecting to the ignition harness, connected to the oil temp sender, I am not sure of its routing. 73-76 had the circuit in the main harness from below the battery area to the center console, where it connects to the center console gauge harness, and a separate wire from the sender to the connection under the battery tray.

Maybe there is a 72 owner here, with the factory oil temp gauge and wiring in place that may shed light on this setup, it would be good to see it.

Thanks Jeff, I've spent more time on the schematics than I care to admit lately and could not find the circuit there (I'll look at the ignition area again though), and this '72 certainly did not have the wire at the engine compartment section of the harness. It does have other early '72 items tho, like early doors and roof, etc. it's MY 05/72 , so that makes since.

I do have a complete '73 Harness that has the temp sensor wire ..and looking at that harness, yes the single wire went over to the passenger's side with the 4 reds to the battery area (thanks for confirming). I questioned this because the temp sender is over on the front left of the engine (doesn't seem logical), but I'm looking at all this stretched out on the lawn. Did it just shoot back across all the heat exchangers on the R side, back over to the sender , I mean it makes no difference really - as I can choose the best path now. Hmm, but what might that be , that's the question. Ideally it would come out of the snorkle somehow. Maybe I'll drop it out of the top of the snorkle solo, down thru the rubber engine seal. I'll figure it out - thanks again.

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On the 76, the oil temp sender wire exits the loom near the battery tray gets routed along the engine hanger bar on it's way to the sender.
It doesn't go any near the exhaust

The temp sender wire on the motor is attached with wire clips to the front of the motor behind the fan shroud, and it goes over to the right side following the engine mount bar.

And if you have the in dash gauge rather than the console, there is a wire added to the harness from the console connection to the back of the instrument cluster.

I agree with Clay on both counts. The wire from the sender to the main harness is a meter long (40") as seen here:
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clip detail
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wire routing
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Then it goes through the engine tin to the connector down below the battery tray. The fuel pump wires and oil temp wires come out from the positive battery cable branch.
I have not seen it on a 1972, and there were no center console gauges then, so possibly just in the combo instrument? But none of the cars I parted out or owned ever had the temp gauge in the combo instrument.

I'm sorry I had it mixed up. 72 is indeed a transition year for this circuit. Late 1971 chassis harnesses had the green/black oil temp circuit in the main harness beginning at terminal 3 of the relay board 12 pin connector, which extends to the dash area, and it is also in the ignition harness - the oil temp sender was optional according to the 1971 schematic.

For 72, no oil temp circuit was provided, you will need to run a separate wire from the sender to the gauge.

On my 72’’ it didn’t have a temp circuit. I had to run it. I have a 74 harness around here. Think I’ll dig out the green/black wire out of it and re-run that wire. Thanks

Thanks for the info.



So I'll be running a complete single wire from sender to gauge in the dash - eliminating 2 extra wire connectors along this wire, cool that can't be a bad thing. No real reason to run it up under the battery box tho , only to swing it back across the engine bar to it's final location. I suspect that was just convenient because of where the battery and fuel pump were (but I've moved those too, so..). Am I missing the point of it getting routed under the orig. battery box area? Is the suggestion to do that again? Basically, how would you route it without battery cables and FP cable coming out where they originally did?
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Wow, thanks for the pics.. that last one really helps my understanding of the original routing

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@Shivers , some elaboration on the path you took with routing the wire thru the harnes/engine compartment would be most pertinent to this conversation. Please?

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You probably will want to have one connector in there, because it will be more difficult to drop the motor if you have to remove the wire first! The GM Weatherpak connectors used to be regarded as kind of the gold standard; good and weather-sealed and not prone to damage from vibration or heat or petrochemicals. Not sure what is the current favorite, though.

--DD

But that’s IF I were running it between the sender and battery box area - I’m trying to just come straight out of the firewall over to the sender. Just unplug it at the sender and drop the engine.

The factory assembly for the sender doesn't allow that. You have to remove the mounting screws for the taco plate to get to the sender. It is behind another plate to protect it from road debris.

So if you run the factory setup, you would have to drain the oil and drop the taco plate to disconnect the sender.

Ahh, I see what you guys are saying, thanks for clarifying that.

Hmm, would it be shear stupidity to just preassembled the plate, grommet and electrical fitting (if available) to the end of a single wire coming out of the harness? ..or am I just trying too hard with that? I know a connection point is not the end of the world, but if it’s not necessary
Thoughts?
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Nothing special, from the engine the wire runs to the clutch cable and wire tied till I got close to the stock rubber snorkel(wire chase). I used an awl to puncture a way into the chase. I soldered the wire to a piece of coat hanger, pushed it through the puncture in the rubber and as I remember (it was 40+ years ago) I cursed it through up to the top of the tunnel and inside.