Technical Brake light switch sensitivity

[fiat500]

It looks like later types of Fiat had microswitches to activate the brakelights rather than the pressure sensor of the 500. Was that to correct the fact that on my car at least, it takes a fairly hefty application of the pedal to make the light come on.
There's nothing wrong with the braking so I'm wondering, is this common or do I have a less sensitive (replacement) switch on mine?

 

[Vitesse]

It looks like later types of Fiat had microswitches to activate the brakelights rather than the pressure sensor of the 500. Was that to correct the fact that on my car at least, it takes a fairly hefty application of the pedal to make the light come on.
There's nothing wrong with the braking so I'm wondering, is this common or do I have a less sensitive (replacement) switch on mine?

I will tell you tomorrow Peter, as the weather looks good for the 500 to come out of winter hibernation. I am getting withdrawal symptoms. I won't put the 126 lump in straightaway as I want to get reacquainted first and I haven't actual driven the car with the 123 dizzy fitted yet.

I must admit I don't think I have to apply hardly any pressure to get the brake lights to come on.

 

[Vitesse]

Ok I had a look Peter there is a bit of travel on the pedal on the spring before the pedal actually engages on the master cylinder. Then once you press the pedal further so that it is actually starts to push the cylinder in within the master cylinder I would say it is about 2-3cm before the lights come on and there is quite a bit of pressure applied and not much further for the pedal to travel.

So what you describe sounds quite normal. I think.

I didn't get a chance to go for a drive but started the 500 up and it is running sweetly after its hibernation.

Someone has dumped a 650 engine in gearbox in front of the car so I need to move that first before I can go for a drive.

Tony

 

[fiat500]

I'll bring round my trailer and help you load that old engine on on and take it to the dump on the way home if you like. Always willing tio help.

 

[DimitriL]

I am having the same issue. The brake lights will only come on if I am at the very end of pedal travel (super hard breaking). My brakes are new and work well. I went under the car to check the brake light switch, and it looks like new. There was still some 4mm thread left to screw in, and my thinking was, okay, I will screw the switch that more in, maybe it will engage faster. That didn't work. It actually looks like I have to press even harder on the pedal. Would the opposite be true? (if I un tighten the brake switch, would it engage sooner)? Anyone has any experience with this? I would like the brake switch to engage as soon as my foot hit the brake pedal. Thanks.

 

[fiat500]

Anyone has any experience with this? I would like the brake switch to engage as soon as my foot hit the brake pedal.

I fitted a new switch because they are not expensive; that made the brake light very sensitive.

 

[DimitriL]

Or would it mean that this switch isn't that sensitive anymore, and better to replace it with a new one? I wouldn't want to put a new one and have the same issue, because I believe the one in the car is actually a new one.

 

[fiat500]

Or would it mean that this switch isn't that sensitive anymore, and better to replace it with a new one? I wouldn't want to put a new one and have the same issue, because I believe the one in the car is actually a new one.

My original one was new but not sensitive. I bought one from eBay...not made for the 500 but the same switch....it worked better. I know what you mean though...new one might not fix it.:bang:

 

[DimitriL]

My original one was new but not sensitive. I bought one from eBay...not made for the 500 but the same switch....it worked better. I know what you mean though...new one might not fix it.:bang:

Thank you. I think I will give it a try as well to buy another one. Did it leak brake fluid when you took the old one out? I saw some hydraulic brake light switches, and they all look the same, would you think that the thread is universal (it looks so)

 

[portland_bill]

I am having the same issue. The brake lights will only come on if I am at the very end of pedal travel (super hard breaking). My brakes are new and work well. I went under the car to check the brake light switch, and it looks like new. There was still some 4mm thread left to screw in, and my thinking was, okay, I will screw the switch that more in, maybe it will engage faster. That didn't work. It actually looks like I have to press even harder on the pedal. Would the opposite be true? (if I un tighten the brake switch, would it engage sooner)? Anyone has any experience with this? I would like the brake switch to engage as soon as my foot hit the brake pedal. Thanks.

Hydraulic switches have always been variable in their operation, even when still being fitted to vehicles new. So many years later, I guess the manufacturing quality is unlikely to have improved. Inside it is simple, a diaphragm with a spring behind it and two contacts. The fluid pressure moves the diaphragm to close the contacts. Its position in the circuit, or in the housing will make no difference to how much pressure is needed to move the diaphragm, or how far it needs to travel to close the contacts.

It is possible that they all have the same thread, or there could be a choice between a British/American thread or metric. Be careful.

The switch is fitted directly into the brake fluid circuit, so some fluid loss will occur. If allowed to drip, it is unusual for air to get in, so should not need bleeding afterwards. Don't delay though.

These switches are mostly sealed by a tapered thread, so tighten only gently enough to seal. Screwing it in further will try to expand the housing, which may prevent proper sealing, or may split it. Some have a straight thread and sealing washer, but you do not have a choice, you have to replace like with like.

 

[DimitriL]

Hi everyone, update: problem solved. I changed the brake light switch with another one, and now the brake lights go on as needed. I have to tell you though that when I removed the switch, enough brake fluid ran out to give me a soft brake pedal. I bought new brake fluid before I started the job. Read the manual, and did the brake system bleeding procedure. Started from the rear right wheel, no air came out, left rear, again no air, only from the front wheels I got air. My brake fluid also looked disgusting, it was good to do this job. Now braking is good and the brake light goes on when stepped on the pedal. Thanks all for your help.