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The component in the ring is located on a threeway joint on the breaksystem on the right side of the car in the enginebay. I recognize it as a pressure sensor of some kind but what does it actually do? (I know the electrical system look like crap. It came like that.)
The component in the ring is located on a threeway joint on the breaksystem on the right side of the car in the enginebay. I recognize it as a pressure sensor of some kind but what does it actually do? (I know the electrical system look like crap. It came like that.)
That is indeed the brake light switch. They are prone to failure, so a good upgrade it to put a relay n so the full current of the brake lights isn't being carried by that switch, only the relay coil current.
That is indeed the brake light switch. They are prone to failure, so a good upgrade it to put a relay n so the full current of the brake lights isn't being carried by that switch, only the relay coil current.
... and a microswitch on the brake pedal gives redundancy and a slightly faster action.
You certainly could do that. Easier to keep the switch and add a relay I think, as it's not easy to find the brake wires inside the car, plus you need to make a a bracket to hold a microswitch. All doable of course.
I have not had a problem with my Brake pressure switch which was replaced new during my restoration 8 years ago. I would retain the old switch and just replace it with new if it did fail. They only cost a couple of pounds so not really worth the while of doing all the alterations to put in a micro switch with new wiring when that is just as likely to fail as the original pressure switch.
Sometimes it is just not worth the bother to change the original design.
I heard the original spec ones had silver plated contacts and did have long lives. It's the replacement ones that have brass contacts and they oxidise and get pitted with the arcing from the load of the brake lights, and they don't last. You'll notice Jaguar put a capacitor across the later ones to reduce the arcing.
Mine has been in place since January 1963 and 130,000 miles. The last time it was tested was a year or so ago and it worked fine in spite of its age and more than a two decades without use. One criticism that I've read of them - it may be unsubstantiated - is that they can be slow to react and the brake lights don't illuminate as early as they could in a system operated from pedal movement. Obviously, a microswitch on the brake pedal can act before there's any pressure in the line. On the other hand, it could be more complicated to adjust.
All
I have owned 5 MK1s and 5 MK2s and have never had the original hydraulic brake switch fail.
I have also had numerous other Jags such as MK7 & MK8 using the same switch and have not had any problems.
I suspect the forum is inventing a problem which generally does not exist.
By all means upgrade your brake lights to microswitch if you do have a problem if you want to go that way.
If you do have a brake switch problem then replacing it with the correct part will enhance the value of the vehicle.
I have seen too many Jags "modified" from original and losing their "Non Restored" basic value.
Bill Mac MK1 MK2 S3XJ6 X300 Previous 14 jags. MK5 to X308 Current Ford falcon Ute Mitsubishi Colt shopping trolley Subaru Forrester (tow vehicle for my aeroplane)
The original on my S Type didn't work when I got the car and the original on my E Type failed, so I have had bad luck with them. The one on my DS420 is still working at least
Help me indentify this component, pls! DS420 -83
