Brake fail light inoperative

[farkamhall]

Just taken my VH for a blue slip and got knocked back on two items, one of which was "brake fail light inoperative". he said this was the warning light on the dash that should light up when you start the car.He checked the switch on the brake cylinder and said that was workink o.k. and suggested it was possibly a bulb or the wiring from the switch under the bonnet that goes to ignition barrel, either way, the dash has to be removed, i believe, to check them out. Can anyone tell me the correct way to remove the dash or an alternative method of fixing the problem, Thanks heaps guys. by the way, the other thing he knocked me back on was steering rack tie rod ends.

[DANNY8]

If it's suppose to come on when u start it....maybe just get the signal from the battery light....so it still comes on when ya start it, and goes off straight away.

Or fix it properly.

[commsirac]

Danny, that wont fool someone who knows the correct operation as it will glow when the igntion is switched on and the motor isnt running, it should only be seen when in the start position.

Havent examined this on the VH, but would anticipate it works like all other holdens from the mid 70s on. If so there will be actually two wires that go to the master cylinder making a bridged connection. One wire comes from the warning light on the dash, the other goes to the ignition switch.

There are a few reasons as to why it may not be working, the globe being out of order would be the least likely....it doesnt really get much of a work out.

Anyway, before you go pulling out the dash to get at the globe(Im sure it cant be that hard) suggest you do the following test:

Turn the ignition to on and find the wires that leads to the master cylinder, remove the wire and earth the end of the wire. If the globe is working it should light up. Im suprised the person doing the rwc didnt do this if they went to the trouble of finding that the switch works.....or perhaps they have no idea, which is quite common with the workings of this part of the car.

If the globe doesnt ligth, problem is in wiring back to dash, globe itself or a failing in the soldered connector that connects the wiring loom to the dash(very common)

If the globe is working, then the problem is on the ignition switch side of things. The second wire that goes to the switch actually goes to the ignition switch and is earthed when the switch is turned to the start position. It is possible this connection has become worn or someone has dislodged it thinking it has no purpose.

Hope the ^ is of some help.

[farkamhall]

thanks guys. commsirac, the guy doing the rwc did take the plug off the switch at the master cylinder end and bridged the connection with a piece of wire and he did do the earth test at that end also sorry, should have said that before, but that is why he seems to think it is either the bulb or the wiring going back to the dash. he said the main cost to repair is the time taken to remove the dash as that is the only way tyo get to the bulb. is that correct do you think? thanks

[commsirac]

thanks guys. commsirac, the guy doing the rwc did take the plug off the switch at the master cylinder end and bridged the connection with a piece of wire and he did do the earth test at that end also sorry, should have said that before, but that is why he seems to think it is either the bulb or the wiring going back to the dash. he said the main cost to repair is the time taken to remove the dash as that is the only way tyo get to the bulb. is that correct do you think? thanks

Going on your description, Im not sure if he has tested it properly or not.

When the plug is removed from the switch, there are two connectors there. Common misunderstanding is bridging these two connections will make the lamp work. No, the two connectors become bridged when they are attached to the switch. The switch operates by making a connection between these two terminals and earth, not by making a connection between the two terminals(they are permanently bridged), so disconnecting them and joining them will make no difference. The whole connector needs to be earthed to the body of the car to test for the operation of the lamp.

suggest you repeat the test for yourself as I outlined in my previous post before proceeding further.

The only way the actual switch itself can be tested is to drain out some brake fluid and see if it activates, to reset the switch it has to be unbolted from the master cylinder, I take it he didnt actually do this.

[farkamhall]

thank you commsirac,you are correct,he did not do that test. i will follow all your instructions and see what happens. will let you know result as soon as completed.many thanks for your assistance.