Brake Warning Light

[TimS]

Guys

New here with a 1979 FHC 2 litre 7. Only 26,000 on the clock.

I'm finding the search facility on this forum keeps timing out on me and I suspect that my query has been answered before but I cannot find it!!.

I have just fitted a NOS brake master cylinder. I have also fitted a new brake pressure warning switch. Problem is that the switch is not making contact to cut the brake warning light off.

Detail - Master cylinder changed, brakes bled, good pedal. Brake warning light on. Removed warning light switch from master cylinder and operate the plunger on the switch - warning light goes off. Replace switch into master cylinder and the light stays on.

I'm puzzled.

Any ideas?

Thanks in advance

Tim

[FI Spyder]

Look in the bottom of master cylinder where the switch fits. You'll need a mirror with it installed. There is a raised surface on the secondary piston that the switch rides on. If the piston has shifted (can happen when bleeding brakes) the switch will stay activated. If the caming surface is out of position, with the switch out go for a drive and apply the brakes hard several times. It may center itself. If it doesn't the piston may be stuck neccessitating removal and disassembly or at least forcing the piston back and forth using a smaller screw driver levered on the caming surface.

Unplug the switch so it doesn't stay activated. I had mine slip off when I was on the road and I just let it stay on till I got back home and it burnt out the switch. Wouldn't make contact after that. Had to get a new switch.

The secondary piston tends to freeze as it normally doesn't move. I had to pry mine out when I overhauled the master cylinder. Because yours was NOS this may be the case even though it's "new".

TR7 Spider - 1978 Spitfire - 1976 Spitfire - 1988 Tercel 4X4 - Kali on Integra - 1991 Integra - Yellow TCT

[TimS]

Thanks very much.

Took switch out of master cylinder, started car and pumped the brakes, replaced swithch, all OK!!!.

Brilliant.

Regards

Tim