Dash electrical gremins

[Wes]

I'm having some trouble getting my gauges to work correctly in my 72 CSL.I've never seen them work as car was a barn find so this may the the issue. However, I'm seeing the following issues.

1. Oil pressure light comes on before engine is switched to crank - is this normal?
2. Taco not reading revs when motor is running;
3. Temp gauge not working nor fuel gauge;

Do seem to have the indicator arrows light up when I push the hazard light button as well as the red light on the speedometer but that wont go off.
I also have headlights.
I'm thinking it may be a simple as poor grounding or a short somewhere as I keep blowing fuses, number 4 in particular.
Was hoping somebody here has had similar issues? If not I'll just keep plugging away to figure it out.

 

[adawil2002]

1.) Both yellow-orange Oil Pressure & red E Charging System lights should illuminate when key is in position 1 & start. Both should go out within 2 seconds of engine running.

2.) There should be a black spade connector behind the Tachometer which is part of the wiring harness.

3.) Either the sensor wires are not connected to the gauges or wires are not connected to the temp sensor or fuel level sender. When locating the temp & level sender wires, when grounded should peg the fuel & temp needles to full fuel & full hot.

Red light on the speedometer is the emergency brake ON telltale.

Clean all grounds to clean metal. Replace all fuses Keep us posted.

 

[Wes]

1.) Both yellow-orange Oil Pressure & red E Charging System lights should illuminate when key is in position 1 & start. Both should go out within 2 seconds of engine running.

2.) There should be a black spade connector behind the Tachometer which is part of the wiring harness.

3.) Either the sensor wires are not connected to the gauges or wires are not connected to the temp sensor or fuel level sender. When locating the temp & level sender wires, when grounded should peg the fuel & temp needles to full fuel & full hot.

Red light on the speedometer is the emergency brake ON telltale.

Clean all grounds to clean metal. Replace all fuses Keep us posted.

This is really helpful.

Thought that was the case with the oil and charging light but wasn't in front of the CS so couldn't go and check.
Not quite sure what you mean in the second sentence under 3.?

 

[Wes]

Couldn't get to the car today so hit the books instead to try and get my head into the game.

Looks to me like I'm missing some relays from next to the battery. I only have two of the round ones, looks like there should be 3 and the rectangular one with the white band.
From memory these are for lights/horns? My blue book hasn't been very helpful.

I don't recall having the two missing relays in the car when I bought it but it was missing stuff.

 

[day66]

The rectangular one is the alternator control box.

 

[Wes]

The rectangular one is the alternator control box.

So I'm assuming without that the alternator wont charge the battery?

 

[day66]

Yes, that‘s right. Not sure though whether that means the charge warning light would not go out or whether it doesn’t light up at all.

 

[Wes]

Yes, that‘s right. Not sure though whether that means the charge warning light would not go out or whether it doesn’t light up at all.

I think mine is staying on all the time.

 

[eriknetherlands]

My car also does not have #3 and it ran fine. (3.0cs auto, carbed). Others may know which purpose it had. Could be an optional one, perhaps foglights or headlight cleaning system?

For sure you need the rectangular one. As it is the alternator control, it would make sense that it causes your check light to stay on.

The reason that all lights go on for 2 seconds when cranking the car is that it offers the possibility to check if any light is blown. It's still the same in modern cars.

 

[Stevehose]

The 3rd relay was for adding fog lights. The other 2 are horn and high beams. The rectangular one is the voltage regulator so you need one of these if your alternator is not internally regulated.

 

[adawil2002]

This is really helpful.

Thought that was the case with the oil and charging light but wasn't in front of the CS so couldn't go and check.
Not quite sure what you mean in the second sentence under 3.?

When the wire to the fuel gauge is grounded it will show a full tank, when the temperature gauge is grounded it will peg the gage needle to hot.It’s a simple test to see if the two gauge wires are connected to the cluster.

 

[sfdon]

#1 relay is horn relay
easy to figure, it has two green/yellow wires, brown/yellow, green/white and red

#2 relay is high beam
easy to figure, it has two white/violet wires, brown, white and red

 

[sfdon]

Fuse 4
red/white
boot light
interior light
hazard switch

 

[sfdon]

If your alt light is staying lit- that means the blue wire has found a ground somewhere. One side of the bulb is battery positive and other side is ground - you have a circuit and bulb lights up.