A quick learning I had today. When I got my 95 coupe last month I had posted that my red brake light was on. The car came with a service record stating it was an issue with the ABS pump and the whole thing needed replaced (for well over $1000). After researching some electrical diagrams, I stumbled on a drawing for the newer ABS system and noticed that the only thing going to the light was the reservoir level switch on it. This can be verified by simply looking at the switch, if you have only 2 wires, you are golden, if there are 4 or 5, then the light is activated by either the reservoir level or accumulator pressure. Since I only had 2 wires, I tested continuity on both sides of the connector. On the plug going to the light it was good (wiring verified good), however with the reservoir visibly full, the there was an open in the switch itself (it should be closed with a sat level). I jumpered the plug and no more red brake light! I do check all my fluids on a regular basis, so will see a lowering level (sign of a leak) well before the float would have seen it anyway). If you have a 95 or 96 and are fighting the brake light deal, might be worth trying, just make sure you check level visually on a regular basis!

 

Famous last words. A ruptured brake pipe caused by an object during a high speed run on a motorway and the first you will know about your loss of fluid is no brakes when the lorry pulls out in front of you. The light is more for this possibility than for a gradual loss of fluid.

 

Replace the faulty level switch!!

 

I plan to replace the switch, but am happy that it is not gonna cost me a grand or so. This is the first car I have ever had with a switch. Then again, can't see any of the lights (until I do the light upgrade) anyway.

 

did you try to add fluid before doing this? My light was on last year for a couple of months and finally turned of when I added an entire bottle of Jaguar brake fluid(maybe a bottle and 1/2) . the reservoir “seemed” full but it was not. It has never come on since, except upon starting the car as it should. Problem was that after the last brake service it was never filled properly.

not to pile on here or tell you what to do with your own car, but I Would urge you to rewire the car as it should be and try to add some fluid. How will you even know if you burst a hose while driving and loose fluid?

 

I changed the original to note that this should be done for troubleshooting to ensure ABS is not replaced or disturbed when it does not need to be (as the dealer has been telling the previous owner and myself for 10 years, even they missed the 1995.25 tech update on the ABS and brake system changes). I appreciate your concern and do plan to replace the reservoir (of course the switch is integral to it and can not be replaced by itself). However, the lines from master cylinder to the calipers is only pressurized upon depression of the brake pedal (hence the reason you have to pump up the pressure in order to bleed the brakes and the reason the reservoir does not empty out when a line is disconnected) so even when driving, with the switch connected, the pedal to the floor still comes as a surprise as you pump out the fluid. The older systems (the ones with the pressure accumulator) have much more normally pressurized parts of the system and that is why the brake light (the red one) is also connected to the accumulator pressure bulb/tank, a fault there in that system will cause a failure of the brakes in normal stopping as the ABS is integral to the normal braking circuit. The brake failures and inability to stop with those older systems is a big part of what drove the auto industry to revamp the systems in the 90s.

 

I’m fighting the same problem on my ‘96 XJS. It’s hard to find a good replacement reservoir so I’m keeping an eye out but trying other methods first. I replaced the fluid in the reservoir last week and that seems to help. I just replaced it again tonight. My theory is there is some junk in the fluid forward of the bulkhead that is making the switch stick. It’s hard to clear that area so I tried pushing some clean fluid through there to see if I can blast out the junk. I used a 30ml syringe with some flexible tubing. If I can’t get it resolved or find a replacement by mid-winter I might cut the reservoir open at the welded seam to gain access and have a plastic welder re-weld the tank for me.