Help with alt and brake warning lights

[Angie]

hey all, on my dash console that is custom made I have added 2 red lights that are for the alt and brake warning systems. need to know how to wire in these 2 lights. the wiring diagrams show notta in haynes and other books. anyone able to help? 1983 truck. Need to know how to wire up the alt/ignition warning light and the 2 lead brake warning wires from the sending unit on the brake equalizer valve thing.

cheers

 

[RonD]

I assume its not the original charging system?
Alternator with Internal volatge regulator?

And master cylinder?


The alternator will have a Light Green wire for the Voltage regulator
That wire comes from the ignition switch, it has 12volts with key on, this wire would PASS THRU a 12volt light bulb in the dash, you would also have a 550 ohms resistor between both terminals on the bulb, this is a backup in case bulb should burn out
When you turn on the key the alternator is a Ground, 0volts, so "Battery Light" has 12v on one terminal and 0 Volts on the other, so it LIGHTS UP.
When you start the engine, and if alternator is working, lol, the Battery Light now has 12volts on BOTH terminals, so it goes OFF
It actually should have 14volts on both, but you get the idea.

This setup is the ON/OFF for the alternator, if voltage regulator is given 12volts all the time it will run down the battery.
So the Green wire should only have Key on 12volts, this is also the Start Up voltage the alternator needs to start "making" its own voltage, so if the light bulb should burn out then no alternator, which is why you need the resistor, but up to you
Resistor is no "required" for the circuit to work, its a safety back up so alternator can always charge battery


The Brake warning light gets 12volts with key on
Then it has 2 possible grounds, the Fluid level in master, or the Parking Brake pedal switch

So on the master one terminal goes to a ground, the other to the Bulb, when fluid is low switch closes and bulb lights up


These 12volt key on sources need to be Fused, they could share the same fuse, 10amp would be more than enough, 7.5amp would do

 

[Angie]

Ron, you need to write a ranger help guide book!! thanks kindly, excellent step by step for what i need to do to get these last couple wires sewed up!!

The master cylinder is just fluid only, the brake proportioning valve has the 2 wire plug on it. I am guessing it is pressure that sends out the ground? didn't know it was for a ground signal, (good to know)! have it wired for positive now, will switch to ground loop closed.

one other question, could the alt light be also wired into the (from) the volt meter wires? (separate gauge) this giving the key on signal.

thanks

 

[RonD]

Yes, any Key on circuit can be used for Battery Light


What year is the vehicle?
Proportioning valve wiring is for the ABS not a Brake warning light, so not a ground setup, in most years
Is there 1, 2 or 4 wires?

Parking brake and fluid level were all the brake warning light was used for

ABS light is different

 

[Angie]

hi ron, the valve looks like this, 2 wires. the truck is 83, this used to be on the frame, had to move it for the build. the light i want to wire this to is grounded currently and the + wire is waiting for the power signal to it. i was lost as to how to connect this valve.

will print off your "how to" for the alt light!! thanks

 

[RonD]

It does look like its the same setup as the Low Fluid Level switch, so one wire is a ground the other goes to light bulb that has 12v with key on.
Or you could run the 12volts thru the switch, if you have already grounded the bulb

Most car makers try to use the Ground as the trigger because its cheaper and can be safer, cheaper because you only need 1 long wire at a relay or switch and a short ground wire
Instead of 2 long 12volt wires, in and out, at the relay or switch

With less 12volt wires around there is less chance of a short and melted wires

So anytime you are adding electrics think "Ground" as the trigger, we tend to think in terms of 12volts as triggers
But much simpler to run one 12v wire to a bank of light bulbs, then one ground wire from each to activated it

 

[Angie]

thanks!

yes its too late to redo the ground triggers on the build, learnt that too far into the systems to rebuild now. will be doing that way next build for keeping it easier.

cheers and thanks for the help again!