Won’t start because the brake lights don’t work

[Bobton125]

I have a PGO 250 road legal buggy
My brake lights won’t turn on when I push the pedal and because of that, it doesn’t start (as it needs the brakes to be pressed for it to turn on like some some bikes/scooters)
I‘ve replaced the switch circled below on the master cylinder, But still does the same thing.
If I put a screwdriver across both terminals of this brake light switch then the lights do work and it does start.

Any ideas what the first things to look at here would be? As I’m very lost
Thanks

[GreenV8S]

That looks like a pressure switch. If you're applying the brakes and the switch isn't closing, you need a new switch.

[smokey mow]

Did you bleed the brakes again after replacing the pressure switch? It could have an airlock.

Edited by smokey mow on Friday 26th June 22:13

[Bobton125]

I replaced the switch with a new one

I didn’t think there was a need to bleed the brakes? I syringed Out what was in the reservoir, replaced the switch and then topped it up again

[paintman]

Bleed the system then try again.

How did you get on with the cable?

[Bobton125]

paintman said:

Bleed the system then try again.

How did you get on with the cable?

I gave speedycables a call and have sent it over to them to replace the inner one

Should all be good hopefully

[normalbloke]

Some of these switches operate at too high a pressure for a lighter vehicle. Ie you’re hard on the pedal before the brake lights operate. Check you have replaced your original switch( assuming that worked properly) for exactly the same. Also check with a meter if the switch works with a hard application of the pedal.

[LimSlip]

A colleague at work has the same buggy and the exact same problem! He also replaced the brake light switch with a part he ordered from PGO and it made no difference just like yours.

I'm wondering if the port in the master cylinder that routes pressure to the switch has become blocked. Easy enough to test, with the switch unscrewed a couple of turns does fluid come out of the threads when you put your foot on the brake?

[Bobton125]

Fluid does come out when the switch is unscrewed

As it’s not working with the new switch and with the system being bled, I am now considering fitting a mechanical brake light switch instead of a pressure switch

[normalbloke]

Bobton125 said:

Fluid does come out when the switch is unscrewed

As it’s not working with the new switch and with the system being bled, I am now considering fitting a mechanical brake light switch instead of a pressure switch

This is what I did on a 56F100 I built. I added a mechanical brake light switch from the rear of a motorbike.basically, any pedal movement equalled the brake lights coming on. Handily, I used the hydraulic switch( which needed a fair bit of pressure to close circuit) as the safety start inhibitor.

[Ritchie230]

The first thing I would do is put the ignition on then put a screw driver across the to terminal on the back of the switch effectively bypassing the switch if your brake lights light and you can start it you know it's going to be a issue with the switch. If nothing changes when you do this then it's going to be a blown fuse of wiring issue. Good luck

[LimSlip]

Ritchie230 said:

The first thing I would do is put the ignition on then put a screw driver across the to terminal on the back of the switch effectively bypassing the switch if your brake lights light and you can start it you know it's going to be a issue with the switch. If nothing changes when you do this then it's going to be a blown fuse of wiring issue. Good luck

If only the OP had thought of this first...

Bobton125 said:

If I put a screwdriver across both terminals of this brake light switch then the lights do work and it does start.

[Ritchie230]

LimSlip said:

If you are 100% sure the brake system is fully bled then it will be either a faulty new switch or the new switch is set to only activate at a higher pressure than the original so there isnt enough pressure being applied.
But a mechanic switch would fix your problem if you think that would be an easier rought to take.

[normalbloke]

Ritchie230 said:

LimSlip said:

If you are 100% sure the brake system is fully bled then it will be either a faulty new switch or the new switch is set to only activate at a higher pressure than the original so there isnt enough pressure being applied.
But a mechanic switch would fix your problem if you think that would be an easier rought to take.

If only these things had been mentioned in the thread already..

[imagineifyeswill]

The fact the lights work and the vehicle starts when you short acroos the terminals tell you the wiring connectivity is fine so the problem has to be somewhere in the switch operation whether a second faulty switch or lack of fluid pressure

[LimSlip]

Now I've found a picture of the PGO brake master cylinder it's actually two independent cylinders (for a split circuit) but with two pushrods coming from the brake pedal. There is no mechanical balancing linkage so if there is air in the circuit that has the switch then it would produce a lower pressure (and less braking). Therefore I suspect it just needs bleeding properly.

Edited by LimSlip on Saturday 27th June 19:49