Caterham Gauge Wiring

[TurboWood]

Hi Gents,

I'm looking for some relatively basic wiring information on the caterham. I'm trying to get the details of where the gauges get their signal. I assume the sensors provide a signal to the ECU which then outputs a calibrated signal to each gauge. Is that right??

 

If that's correct, does anyone know what the signal to each gauge looks like? Is it a simple 0-5V signal?

 

Thanks!

 

Daniel

[Klasik-69]

You need to give more info since different years provide different technologies. Oil pressure comes from the oil pressure sender which is a variable resistor on most engines. 12 CDC is applied to the sender via the gauge. Same goes for the temp gauge & fuel gauge. The tach signal originates from the coil or the flywheel sender on some cars, tach sender on others. Speedometer comes from the tranny cable hookup while many modern cars today get the signal from the ECU after a signal is provided from driveshaft, wheel rotation or transmission output shaft. The 0-5vdc signal you're referring to is likely only used for the TPS or MAF, or other electronic type of signal output. Best thing to do is look at you wiring schematic to see what is going where.

[TurboWood]

Thanks for the feedback, I was definitely too vague. That probably tells you how lost I am/was.

 

I did some digging into the wiring diagram. This is for a CSR.

 

- Oil Temp: All wiring from sensor to gauge is on vehicle wiring harness (good to go)

- Speedometer: Same as oil temp

- Fuel level: Same as oil temp

- Oil Pressure: Oddly the signal wire is coming from the Tachometer plug??

- Water Temp: From engine harness

- Tachometer: Four wires go to engine harness

 

I believe the water temperature is straight forward. I just need to find a way to get the signal from the engine to the engine plug on the vehicle harness side.

 

I'm confused about the oil pressure gauge though. Why would it get the signal from the tachometer? Is one of the four wires feeding the tach originating from the oil pressure sensor? Does anyone know the specifics of the four wires coming from the engine harness to the tachometer?

 

1) Oil pressure?

2) Engine speed

3) ??

4) ??

 

Daniel

[jlumba81]

The wire might be for the gauge light

[TurboWood]

I just noticed you were from Alaska...wow! I hadn't expected to hear of a 7 there. Cool

 

I was able to figure out the light. All the gauges have a red-white wire that is linked to the light switch.

 

I did just discover that one of them is connected to a 12V source via a 680ohm resister, but I don't understand why.

 

1) Oil Pressure?

2) Engine speed

3) Power through 680ohm resister (Brown-Yellow: NY)

4) ??

 

Unassigned wires:

White-brown

Black-blue

White-black

 

Daniel

[xcarguy]

Oil pressure; maybe picking up power for the gauge via the tach contact. Just a Stab.

[jlumba81]

There's 3 more Caterhams up here in Alaska. Alaskaossie is a forum member, but the other 2 are not. Found a link for some CSR documents including a wiring diagram.

[TurboWood]

Thanks, that's the exact link I used to find the vehicle wiring diagram.

 

What I can't find is the engine harness wiring diagram. There is a cosworth diagram, but it only shows the size of connectors and layout of the harness. It doesn't give you the details of wire color or route.

[BruceBe]

The Cosworth diagram does indicate destination wire color in the connector pin-out descriptions. Also, the distance (in mm) between branches of the loom or pigtails is also notated in the drawing.

 

-Bruce

[TurboWood]

Right you are! The format was not immediately obvious to me, but I get it now. So, let me refine my questions.

 

1) Rev signal from ECU to tach. Does anyone know what type of signal this is? 0-5V?

2) Malfunction signal. Can anyone confirm if this is on when grounded (ECU grounds the line to activate malfunction indicator light on tach)?

3) Oil pressure signal. The signal side of the pressure sensor is spliced with the tachometer and ECU. The other side is run to ground. How does this work? Why does the signal go to the tachometer?

 

Thanks,

Daniel