era dash brake warning light

wemooz · #1 (**permalink**) 01-06-2014, 09:24 AM

My ERA #290 had the old style brake warning light on the dash. The master cylinder switch died and was replaced by the new switch which does not activate the light, and I did not cut off the old switch wiring. I would like to connect the dash light to the radiator fan circuit so that when the fan is on the light is illuminated. On the wiring diagram this is a no brainer, but I am not sure about locating the shortest and easiest route for the wiring. Any suggestions or comments are welcome.

strictlypersonl · #2 (**permalink**) 01-06-2014, 01:50 PM

*Note... I'm going to have to check the logic below before you do anything. I'm worried about inadvertent feedback...

This might work, and it will save having to run a wire through the firewall:

Connect one side of the light to a switched power source. (i.e. piggy-backed on one of the green-wire connections at the fuel gauge or tachometer.

Connect (piggyback) the other side of the light to the fan override switch terminal with the blue wire.

(This will only work if the thermo-switch will absorb the extra current from the bulb. If if can't, the automatic function of the fan will no longer work, and you'll have to run a wire to the fan relay power side and ground the other side of the bulb.)

wemooz · #3 (**permalink**) 01-06-2014, 03:55 PM

My wiring diagram shows that the brake warning light was connected to the now discarded brake warning switch by a wire labeled "P", which I assume is in the bundled wires that used to connect to the old warning switch. It seems to me that if I could locate this "P" wire, I could run a wire from it to the hot lead to the fan, which is coincidentally labeled "P" also, and which is between the fan and the fan relay. Both of these points are on the engine side of the firewall and maybe not so far from each other. If this were done, the indicator bulb would be connected in parallel with the fan. If this might work, how could I locate the "P" lead from the brake warning light?

strictlypersonl · #4 (**permalink**) 01-06-2014, 04:44 PM

Bill,

Not a bad idea. You just have to strip back the bundle going to the master cylinders.

wemooz · #5 (**permalink**) 01-06-2014, 05:28 PM

OK, I strip the bundle, but please tell me how I determine the correct wire. My diagram does not indicate the color of the wires.

Ron61 · #6 (**permalink**) 01-07-2014, 03:01 AM

If your old wire was connected from the warning light to the fan lead and is not cut off at both ends, you should be able to put a toner on it at the light end and then check the wires at the end it is cut off at and see which one the tone is on. If you can see your warning light you may also be able to see the color of the lead that is attached to it. Then look for a cut off lead that color and if you have someone to watch just touch it with a voltage source and see if it lights.

Ron

strictlypersonl · #7 (**permalink**) 01-07-2014, 04:52 AM

The old violet wire from the master cylinder switch is the one to piggyback onto the fan relay wire #41.