ABS issues with Accumulator or pressure switch

Can anyone explain why my ABS light goes out after pressure builds up but brake warning light doesn’t? Fluid reservoir is full, brake warning relay has been removed and bench tested. Accumulator or combined pressure switch are my prime suspects. How can I determine which is at fault? The pressure switch looks to be cross threaded into pump body. Is this normal?

David,
I had the same problem a couple of years ago with the red BRAKE light staying on when the amber ANTI-LOCK went out after starting in my wife’s 1990 XJ-S convertible. It was due to a failure of one of the three pressure switches in the Combined Pressure Switch.

I got a good used replacement on eBay and that fixed the problem.

It sounds like your car must have been worked on before in this area and whoever did that work damaged the Combined Pressure Switch.

I posted a lot about this problem and how I fixed it on this list as it happened. Search the archives for “Combined Pressure Switch” and you will get all the info that you need.

BTW, there are two different designs of the Combined Pressure Switch and they work differently and are not electrically interchangeable. This info is covered in my posts from 2017 and 2018.

Paul

Thanks Paul! Big time help appreciated.

David,
Well that is what worked for me. I considered two possible faults at the time, the Combined Pressure Switch and they brake fluid level sensor in the reservoir. It seemed from my testing that the Combined Pressure Switch was the most likely suspect and I lucked out when the replacement one fixed it. I needed to purchase a new large wrench on eBay to remove the Combined Pressure Switch because I did not have anything that fit and I did not want to mess it up.

Paul

Did you have to bleed the brakes after? I am afraid that if I remove the CPS that I will not be able to install a new one with threads possibly damaged. Shouldn’t be at an angle should it? Dave.

David,
I bled the brakes afterwards. Bleeding ABS brakes is different than regular brakes. I followed the procedure in the XJ-S Repair Operations Manual (ROM).
Attached are two pictures that I took of the Combined Pressure Switch in my wife’s 1990 XJ-S convertible before I removed and replaced it. It is also tilted as the one in your picture. I don’t believe that you Combined Pressure Switch is bent based on your picture alone but that the bore in the housing is a little tilted as our’s was.

Paul


David,
Please read up on the ABS system and make sure you depressurize it before trying to remove any components like the Combined Pressure Switch or Accumulator. The ABS system pressure (1,200 PSI?) is dangerous unless depressurized before work. The procedure is in the XJ-S Repair Operations Manual, mentioned in Kirby’s book and discussed numerous times on this list. Make sure that you know what you are doing before working on ABS components and do wear protective eyewear.

Paul

Paul, Thanks for the pictures and the information. The angle of the CPS in your wife’s car is identical to the way mine is mounted. Very encouraging to know that this is normal. I will proceed with caution when replacing. I have a complete set of shop manuals that my mechanic gave me when he retired. I guess he felt a little guilty about all the money he made from me over the years. Looks like your wife’s car looks like mine. Thanks again, Dave.

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David,
I believe in keeping that balance of pictures in the universe constant. So in response to your two pictures here are two pictures of my wife’s Signal Red Classic Collection 1990 XJ-S convertible.
:wink:

Paul

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Very nice! I have 5 wire wheels on my car and no intention of ever going back to original. I have one original that was a spare until I bought another wire wheel. Is this something that you might be interested in? Just sitting in storage.

David,
Thank you for thinking about me with your spare original wheel, but I don’t need any additional wheels. I have several spare good original painted alloy lattice wheels that I picked up along the way as well as a couple of sets of the chromed alloy lattice wheels that the dealerships had chromed including the ones currently on my wife’s car in the pictures. I also recently sold a beautiful set of five chromed lattice wheels to someone whose XJ-SC Cabriolet was in a bad accident and most of the wheels were damaged. It is time for me to downsize the large assortment of extra parts that I accumulated over the past 20 years of Jaguar ownership.

Paul

That’s understood! Any spare CPS in your inventory?

David,
No, I don’t have any spare Crankshaft Position Sensors (CPS), Jaguar Part numbers DAC4606 or DBC12507 to sell. However I have seen used ones show up on eBay for $50 or so and new ones about $80-100 US, so they are available and not that expensive.

Paul

switch

Paul_M_Novak

      [Paul M. Novak](https://forums.jag-lovers.com/u/paul_m_novak)

      Patron

    September 1

David,

Please read up on the ABS system and make sure you depressurize it before trying to remove any components like the Combined Pressure Switch or Accumulator. The ABS system pressure (1,200 PSI?) is dangerous unless depressurized before work. The procedure is in the XJ-S Repair Operations Manual, mentioned in Kirby’s book and discussed numerous times on this list. Make sure that you know what you are doing before working on ABS components and do wear protective eyewear.

Paul