Has anyone found an alternative for the Jaguar JLM1908 which is no longer available new?
I saw a post suggesting GM p/n 2553-3700 with a question mark. Amazon offers a new 2553-0882
for just over $100 and the picture looks similar. Threaded end looks right as does the terminal/plug configuration.
Just wondered if anyone has a recommendation.
Thanks as always.
Thereās an entire thread on here somewhere. There are two distinct types of pressure switch, and their operation is reversed: One is NO while the other is NC. The original one in the XJ-S works the wrong way so thereās a relay in the circuit to reverse the operation. Supposedly that early switch is discontinued. Installing the later one ā which screws right in ā involves removing the relay and using the operation of the switch unadulterated.
Note, also, that IMHO the Teves III is too dangerous to be trusted. Rather than spending to keep it working, money would be better spent either retrofitting the earlier non-ABS vacuum boosted brakes or the later Teves IV system.
PatrickO,
When I had a failure of the JLM1908 Combined Pressure Switch in my wifeās 1990 XJ-S convertible in 2018 I sourced a used one on eBay and that fixed the problem with the red BRAKE warning light being on constantly. Now both the red and amber lights come on and go off as described in the Drivers Handbook. Be advised that in addition to the blue JLM1908 Combined Pressure Switch, there was also an earlier black one, JLM1465, which is different electrically. I believe that the XJ40s used the blue JLM1908 and so there should be plenty of used ones around as people part out those cars.
I posted all about this in 2018 when I had the issue and fixed it. You should be able to easily find those posts by searching the archives for āJLM1908ā.
Paul
Thank you, Paul. I did follow that thread; it was the source of my wondering if an alternative (GM?)
might be available. I guess not.
This is a customerās car and I really hate to install used parts. I will if that is the only option.
The system works fine, just a (false) warning light.
I just want to exhaust the possibilities of finding a new part, Jaguar or otherwise.
Weāll see what happens. If I should find a new replacement Iāll post info here.
Thanks again.
Patrick
Thanks for the information, Kirby.
Iām aware of the differences. In fact, just a couple of weeks ago I had a customer with an earlier car
('89) which should have had the earlier switch but at some point a complete pump /switch assembly had been installed. It had the later (blue) switch and therefore the red warning light worked backward. Light off at first, then on when pressurized. I just wired in a (āinversionā) relay and it worked properly.
What is your concern with the Teves III system? Iāve never seen a complete failure but now youāve got my attention.
Patrick
Patrick,
I have no idea if an alternate GM part will work. I was satisfied when a used Jaguar part from an XJ40 worked and fixed our constant red BRAKE light.
BTW, please remember to depressurize the ABS per the Repair Operations Manual (ROM) before working on the Combined Pressure Switch. ABS Pressure is something like 1,500 PSI and can be dangerous.
Paul
If a flex hose to a front brake fails, you will have no brakes.
You will still have the handbrake, although the US has not interest in testing for it working. In the UK, it has to be working and be able to stop the car in an emergency.
Technically it is only a parking brake, not very good at that job either, Calling it an emergency brake is a stretch.
Agreed. Iāve been around these cars from their introduction and I donāt think Iāve EVER seen one that would stop a car in motion.
Mine would, after I rebuilt it. I upgraded to vented rotors and then reinstalled the used handbrake pads. Rebuilt the handbrake self-adjusters, clearing out all the solidified grease and lubing them properly. Then, when rolling again, I wanted to make sure those handbrake pads were seated properly on the new thicker rotors, so I used them a bunch of times to stop the car when doing everyday driving. They actually worked pretty well. I certainly would not trust them in any situation where the brakes would get hot, though; I think those tiny pads would get incinerated in a heartbeat.
All that said, Iād hate to be having to find that handbrake handle in a panic when the brake pedal goes to the floor ā which is what would happen if a front brake hose blows. And Iāve had a front brake hose blow, although not on my Jag ā itās definitely cause for a change of underwear. Heck, when I had a rear brake caliper failure on my XJ-S ā which is what precipitated the rebuild and rotor upgrade ā that was enough of a panic for me, and I still had working front brakes!
Nice work! ā¦and with used pads!
Then thereās this: āXJS inboard-braked handbrake improvementā on this site.
Well, with the thicker rotors it would have been difficult to assemble with new pads. In fact, I might have had to grind them down to look like used pads to get them in.
If I had it to do over, Iād do what someone else suggested and toss those OEM pads over the hedge and buy some pads to fit some tiny Japanese car and cut them down to fit.
Hello Paul! Iāve been very appreciative of the posts youāve made on the brake light issue and I believe I have the same issue in my wifeās 1990 XJS. But, before I go buy a new switch, I was hoping to test my current switch and I thought I recalled you running continuity tests on the pins. Where can I find the continuity test pattern for the blue combined pressure switch?
Thank you!
Trevor
@Trevormdavis Use the spy glass and search for ācombined pressure switch continuity testā and the first response might have what you are looking for.
Trevor,
Thanks. I have been on Jag-Lovers for 23 years and try to share with others what I have learned while working on the several Jaguars that I have owned and worked on. I am thankful that I found Jag-Lovers because I wouldnāt have been able to keep my Jaguars running or looking their best without it. I enjoy giving back to a group that has helped me so much.
I found the information on the three switches inside the Anti Lock Brake System (ABS) Combined Pressure Switch in Figure 28.1 āANTI-LOCK BRAKINGā of the Jaguar XJ-S S57/90 Electrical Guide. The attached photos plus the information below should help you sort things out. The S57 shows that the ABS Combined Pressure Switch connector has a Black (B) wire going to pin 1, a Black-Light Green (BLG) wire going to pin 2, a Purple-Green (PG) wire going to pin 3, a White-Purple (WP) wire going to pin 4, and a White-Blue (WU) wire going to pin 5.
With no pressure in the ABS, there should be continuity between pins 1 and 4, no continuity between pins 1 and 2, and no continuity between pins 3 and 5. Once the ABS is pressurized properly all three switches should change state and there should be no continuity between pins 1 and 4, and continuity between pins 1 and 2, and continuity between pins 3 and 5.
When I had this problem, one of the three switches inside the Combined Pressure Switch was not behaving this way. I canāt remember which one right now, or whether it was while pressurized or unpressurized but I probably posted this finding and it is likely in the archives.
Please remember that the ABS has 1500 PSI (or more?) pressure in it and should be properly depressurized following the procedures in the XJ-S Repair Operations Manual (ROM) before removing any components, like the Combined Pressure Switch.
Paul
Trevor,
I looked back through my records and confirmed that my original ABS Combined Pressure Switch failed the continuity test between pins 1 and 2 which caused the red BRAKE light to illuminate. Unpressurized there was no continuity between pin 1 and pin 2 which was correct, but with the ABS pressurized there was also no continuity between pins 1 and pin 2 which was incorrect. I remember this now because I wasnāt sure that the replacement Combined Pressure Switch from an XJ40 was going to work properly until after I installed it and pressurized the system. I was quite pleased when the red BRAKE light went out when the ABS was pressurized confirming that not only had I diagnosed the failure correctly but also that the replacement Combined Pressure Switch actually fixed the failure.
Paul
Paul, this update is INCREDIBLE! Thank you for the detail and time spent putting it together to help! Iām getting in the garage today/this weekend and will report back on our XJS.Thanks so much!
Trevor
Paul, u mention the problem about the BRAKE light being on constantly, but otherwise did the defective JLM1908 not cause your brake system to operate properly?
Paul - I promised to get back to the thread on progress. Well, I was able to use your description above to work slowly through diagnosing the Combined Pressure Switch, and to my surprise everything worked exactly as it was suppose to on the male side of the switch! All the continuity worked according to your direction. So, I did two things: 1) I thoroughly cleaned all the connection points in the male and female side of the connector (used 2000 grit sandpaper and q-tips to remove contaminants) and use a small screwdriver to tighten the female connection points to ensure a proper connection to the male side. and 2) I did a brake fluid flush and refill to see if there were simply issues in fluid pressure. Well, one of those two things worked and the light is off! Unfortunately, I ran an imprecise experiment as I did both fixes at the same time, so I am not sure which one actually fixed the issue:)! But, the wife drove it all Sunday with no issues.
Thanks again for your continuity test clarification or else I would never have been able to rule out the switch as the culprit! Happy motoring!
Trevor
1 Like