Looking for coolant temperature gauge sensor on 85 Westy

[Mystery_Machine]

After having the engine in my 85 Westy replaced, my coolant gauge which was working, no longer is. I suspect it's either the sending wire isn't connected to the temp sensor, or the new engine has a bad sensor.

I've read a number of different threads on the subject and consulted the Bentley manual, but remain puzzled as this is all new territory to me.

In the first photo, I see what I think is a blue Temp 2 sensor on the left. Immediately to the right of it, is what I thought is the coolant temperature gauge sensor. Given there's nothing connected to it, I thought "Ah! There's my problem." After looking everywhere to no avail for the red / yellow wire that I thought should be connected to it, I traced a wire (originating from the same group of wiring that includes the pair to monitor the coolant reservoir level) that leads down underneath the engine. I can barely see it, but it appears where the sheath ends, it looks like perhaps it's yellow / red. It's very difficult to see, but I've tried to capture it in the second photo

Is this possible? Is the blue sensor that has a connection the Temp 2 sensor? Is the blue sensor next to it the sensor for the coolant temp gauge? Is it possible the coolant temp gauge is near the bottom of the engine?

Thanks in advance for your assistance.

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'85 Westy

[skills@eurocarsplus]

the wire in your 2nd photo is for the oil pressure

you for sure are missing the wire for the temp sender.

if no one replies, remind me tomorrow via p/m and i can snap a pic for you.

i can't remember what part of the harness that wire exits from, but i'm willing to bet it's the same spot the the other temp sensor harness comes out of
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[Wildthings]

The yellow/red wire goes to the temperature sender and not the oil pressure sender. Looks like you may have a 2.1L block so your oil pressure switch may be in the wrong location for the correct wire to reach it. The oil pressure switch take a blue/black wire according to the schematic.

[Mystery_Machine]

Thank you Wildthings and skills for the quick response.

Is it possible that the wire for the coolant temperature gauge is incorrectly connected to the oil pressure sender? I know...it's difficult to tell from that picture exactly what color that wire is.

There's only additional wire that is emerging from the this same wiring harness that I can see that is disconnected. That's this green lead.

Skills, if you can snap a picture of exactly which wiring harness has the lead for the coolant gauge temp sender, that will be immensely helpful.

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'85 Westy

[Wildthings]

The green wire may be for a tach and thus not used.

You oil pressure and coolant wiring go through a 7 prong connector which may be in the black box with the FI and fuel pump relays.

[djkeev]

Green is often for the tachometer and hooks to the ignition coil.

Dave
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[4Gears4Tires]

The smaller temp sender next to the blue plug is where the dash reads the coolant temp. As you don't have anything connected there, the dash coolant gauge won't work.

Look for any loose spade connectors.
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'87 Syncro Ferric Oxyhydroxide Superleggera Edition
'85 Westy Sciuridae Domus Edition

[Mystery_Machine]

Thank you everyone! The first mystery of the failed coolant temp gauge is solved with your help.

I traced that lead and found the yellow / red wire routed to beneath the engine. It may have been connected to what Skills@eurocarsplus, you identified as the oil pressure sensor? As you'll see in my previous picture, it was very difficult to see. It did however look like it was connected to this. In any event, I retrieved it and connected it to the temp sensor and its working again. Thank you!

I've looked but am unable to find the blue / black wire for the oil pressure sensor. And now it has me wondering if the oil pressure light isn't lighting at ignition turn-on because now this sensor is missing its lead.

My one other question is what this green wire with a yellow connector is intended for. Wildthings and djkeev, you both suggested it could be the tachometer, but the tach is working. And I do see a green wire going to the coil. Any thoughts as to what else this might be? I don't know if this is a generic plug, in which case these may not be relevant, but the plug has 161 871 880 D printed on it.

Again...many thanks for your help!

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'85 Westy

[Wildthings]

Do you have the stock tach built into the dash or some kind of aftermarket one? The green wire would have been used with a stock unit. What wires are connected to the negative (-) side of your coil?

[Mystery_Machine]

Yes. The tachometer is stock. It's working well. As requested, here are pictures of the wiring to it.

And I'm still unable to find the blue / black lead for the oil pressure sensor.
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'85 Westy

[Wildthings]

On a 2.1L there is a two lead connector towards the left front of the engine compartment where a harness for the two oil pressure switches plugs in. I would guess that the oil pressure switch wiring (or a connector for such) for the 1.9L would likely be in the same area.

[Mystery_Machine]

Thank you, WildThings. Will do some further reconnaissance to see if I can track down the blue / black wire for the oil pressure light.

Do the photos of the coil that I posted help to identify what the disconnected green wire with the yellow connector could be?
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'85 Westy

[Wildthings]

[Mystery_Machine]

It’s difficult to tell whether it was previously connected. It certainly looks like it has been living in the engine bay for 36 years, but tough to tell what it has been doing during that time.
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'85 Westy