Indicator Light Question

[Discseven]

Have just pulled my Temp / Oil Pressure guage and found the top indicator light slot in the guage has nothing there. ('80) What's this indicator for?

[targa80]

What ever it was originally for has been deleted in the 1980 version that I have. I ended up using it for the factory alarm active indicator that I added with a keyless entry module.

[Discseven]

Thanks Pat. You seem confident in your answer. I'm still a bit spooked... there's taped off wiring just behind the Temp / Oil Pressure guage. I realize now that I should have taken the tape off and checked the wire color. Will do that tomorrow and post image.

[targa80]

[QUOTE=Discseven;8182258]Thanks Pat. You seem confident in your answer. I'm still a bit spooked... there's taped off wiring just behind the Temp / Oil Pressure guage. I realize now that I should have taken the tape off and checked the wire color. Will do that tomorrow and post image.[QUOTE]

I have been reinstalling all of the original harnesses back into the car and each circuit has been buzzed out per the schematic. I was unable to find any lamp that was correlated to that opening. If anyone knows what it was originally for I would like to know?

[catuck]

O2 sensor? Just a guess.

[porwolf]

I found this picture of an oil pressure/temperature 911 gauge on the internet and it looks like the top indicator light is intended to be connected to the brake system?

[porwolf]

Actually I got the picture from an evilbay offer. This is the back side of it, looks like 5-76 build:

[Discseven]

Thanks for input guys --- and for images Porwolf. Back of guage you posted Porwolf is exactly like my '80 temp / oil pressure guage (shown below). On Porwolf's guage, it appears there's a connection at post marked #6. I have no connection on this post.





The wrapped / disconnected wire I found behind the temp /oil press guage yesterday... here's wire unwrapped. It has a female spade-end and the wire's clearly suffered a partial meltdown.





The origin of the "toasted" green wire is from the cabled bundle where other temp / oil pressure wires exit from (at arrow). You can also see the vacant post here. It's just under the spade of the toasted wire:





With the spade on the end of the toasted green wire...and a suggestion that there is a connection at a post where my guage has a vacant post... and the toasted wire exiting a cabled bundle where other temp / oil press wires exit... the pieces of this puzzle together suggests the toasted green wire might connect to the vacant post my guage has... BUT... my guage seems to function fine with the vacant post as is.

I'm not an electrical guy so I'm not sure what to do with this. Suggestions please --- with the exception of saying "Connect the toasted wire to the vacant post and see what happens."





I've searched around under the dash for a light, brake or otherwise --- thanks Porwolf for posting the "brake" photo... but nothing was found.

My thoughts --- sometimes we mess with things like this only to make matters worse. Perhaps with a working guage (at least it seems that way), I should leave well enough alone. Again... suggestions are invited. More to the point on toast, if you know exactly where this green wire goes, that would be the holly grail here!

[porwolf]

From the backside picture (not my speedo) that I posted it looks like your empty post should be a ground connection. It has that ground symbol (three horizontal lines topped by one vertical line) on the black plastic base.

As far as the melted "green wire" is concerned from my '78-'83 Bentley SC manual's electrical diagrams I take that there are 5 wires with green color connected to the oil gauge:

1. Green/Red: Oil Pressure gauge
   2. Bllue/Green: Generator Charge Indicator Light
   3. Green/White: Oil Pressure Indicator Light
   4. Green/Black: Oil Temperature Gauge
   5. Green/White: Oil Level Indicator Gauge

I am still not positive about what the third indicator light on the top of the oil indicator gauge is for. But i do remember a discussion on the Pelican board about it in the not to distant past. I let you know when I find it.

[porwolf]

Here is the thread trying to identify all the indicator lights of the oil gauge I was thinking about. For the top indicator light it suggests being an "idiot light" having something to do with the CIS system. Maybe it does not apply to '79 or '80 SC's and is not used for those models. Maybe it's just a hold-over from earlier vintages.

simple question about gauges! need some beginner advice :)

[javadog]

ONCE UPON A TIME, the handbrake light was located at the top of that gauge. In 1976, they moved it to the dash, with the seat belt light.

So, from 1976 on, there is an extra, unused light.

JR

[Discseven]

Thanks Porwolf for looking up the wires and the link. I'm going to check my wiring against your color codes. Given what you, Pat, and others have said, I'll let sleeping dogs lie in regards to the plugged top indicator in the temp / oil press guage. Am still looking to sort out the green wire --- first a check of the existing connections per your codes. I appreciate the note on the ground symbol too --- thanks!

[porwolf]

Discseven, thanks for bringing up the issue of the mystery 3rd indicator light on the oil gauge. Now I am thinking of hooking it up as an indicator light for either the fuel pump and/or the air flow switch.

[Discseven]

Originally Posted by porwolf

Discseven, thanks for bringing up the issue of the mystery 3rd indicator light on the oil gauge. Now I am thinking of hooking it up as an indicator light for either the fuel pump and/or the air flow switch.

Interesting idea Porwolf --- we might as well use that slot for something. Please elaborate on your thinking... as in what the light would indicate? Low pressure? Broken circut? And what "air flow switch" are you referring to?

[Discseven]

Originally Posted by javadog

ONCE UPON A TIME, the handbrake light was located at the top of that gauge. In 1976, they moved it to the dash, with the seat belt light.

So, from 1976 on, there is an extra, unused light.

JR

Very definitive note JR --- thank you.

[spuggy]

Originally Posted by javadog

ONCE UPON A TIME, the handbrake light was located at the top of that gauge. In 1976, they moved it to the dash, with the seat belt light.

So, from 1976 on, there is an extra, unused light.

JR

Seem to recall the Owners Manual for my '77 says it's for the Sportomatic over-temperature warning light (sporto's shared the engine oil), where fitted.

[E Sully]

It would definitely seem a previous owner had hooked that wire up incorrectly.
Do you have the owners manuel for your car? I would think it would explain what the gage indicator lamps are for in the instruments.
I don't have a diagram for your car, but the only green wires used that I know of are for the fuel sender, wiper motor, sportmatic oil temperature, electronic speedometer, and a/c.

[Discseven]

Originally Posted by E Sully

It would definitely seem a previous owner had hooked that wire up incorrectly.
Do you have the owners manuel for your car? I would think it would explain what the gage indicator lamps are for in the instruments.
I don't have a diagram for your car, but the only green wires used that I know of are for the fuel sender, wiper motor, sportmatic oil temperature, electronic speedometer, and a/c.

I do have the manual Ed... good idea to look at it! I haven't looked at it for years --- our forum being the defacto place to go You guys are GREAT!

[targa80]

These two pics are from the part 2 of the 1973 schematic with my note on the green wire that goes to the large combination gauge (Temp /Oil Pressure). You can save these pics to your computer and enlarge them for clarity in a viewer program. The schematic and legend is on the host web site.







Attached are the photos of my 80SC gauges prior to dismantling the car in 2002 for a restoration.

This pic is of the Large combination gauge (Oil Temp/Pressure gauge) in question and you can clearly see the open light socket and the green wire is in the lower left side of the pic and the female terminal is not connected to anything, it just lays in the back of the harness. There is a green wire that is connected to the small combination gage (Fuel/Oil Level Indicators) This green wire is for the fuel indicator from the fuel sending unit. As I stated earlier in this thread, "I was unable to find any schematic showing this unconnected green wire is used on the 80SC".



This pic is the Clock and the Odometer wiring for reference.



This is the Tachometer wiring for reference.

[Discseven]

Originally Posted by targa80

Attached are the photos of my 80SC gauges prior to dismantling the car in 2002 for a restoration.

This pic is of the Large combination gauge (Oil Temp/Pressure gauge) in question and you can clearly see the open light socket and the green wire is in the lower left side of the pic and the female terminal is not connected to anything, it just lays in the back of the harness. There is a green wire that is connected to the small combination gage (Fuel/Oil Level Indicators) This green wire is for the fuel indicator from the fuel sending unit. As I stated earlier in this thread, "I was unable to find any schematic showing this unconnected green wire is used on the 80SC".

Great diagram and pics Pat. Focusing on the green wire in the diagram, it appears that wire does terminate (small orange arrow below) off the guage as I read it. (Thanks for posting other guage pics. I was wondering about back of tach related to another project I'm working on: Clearing Fuel Guage Fog Without Removing Glass ...actually it was that project that led to this thread.)



And the photo (taken in 2002!) with your '80 green wire coming out of the temp / oil pressure cable and it not being connected (I see it)... and your empty "post #6" (according to Porwolf's reference)... we're at the holy grail here. Great stuff! I suggest this being good confirmation between our '80's (and for similar years) that the "hanging green wire" coming from the temp / oil pressure harness is mute. More, your top indicator light is --- like mine --- vacant. Porwolf's suggestion to use that vacant space is an excellent idea. We should think about that.

Guys... read the "CAUTION" note in the diagram's legend that Pat posted (just above this post.)