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Hello to all
This is my first post on any Lotus Forum. I have owned my beloved 1994 Esprit S4 for 22 years - longer than I have been married to my wife, and yes the car did feature in the wedding photos!
So far I have managed to keep her on the road with the aid of Google (for parts), the Lotus service manual and the excellent Freescan application. Now however the ABS system is threatening to upset all of that - my fear being the unobtainable pressure switch.

The problem: flashing ABS after a few braking events. Brakes seem normal in feel.
Took it to main dealer for Tech 1 read - the only recurrent code is A062 "Low accumulator pre-charge".
The Lotus dealer has a literal interpretation of this - it needs a new accumulator bulb. My independent garage (PNM engineering) say these problems are always the pressure switch.

I did the test suggested on this forum:
1. Brake pump runs every second brake press. It runs for about 1.5 seconds each time. The service manual says that code A062 is set when the controller detects short run times of < 1.4 seconds.
2. Following depressing brake pedal hard 40 times with engine off the pumps runs for between 25-28 seconds after ignition on - the forum suggests this should be 30-60 seconds.

My interpretation (for others to correct) is that the accumulator is weak but not toast yet. The pump is however running for a shorter time than suggested meaning a possible early switch off from the pressure switch. I don't have access to the inline pressure gauge needed to check the switch off pressure. The service manual indicates that this could be a discharged accumulator or a poor switch point condition of the pressure switch.

I have seen a listing for a new accumulator (will find out on Monday if actually in stock) - however it is about £250. I have a nagging doubt that it will not solve the problem.

Would people advise that I try to clean the pressure switch first? Can that procedure damage the switch further? Is there any further news on a re-manufacturer of the pressure switch (I don't think I would go to the extent of removing the ABS system and replacing)?

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Upgrade today to remove Google ads and support TLF.

I’m pretty certain other folks have used a different accumulator off something else with no problems. Have a search on here - I know I’ve seen it posted. And they are cheap as chips

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I suggest you do some serious legwork on here, there’s a lot of information on the Delco system. The Range Rover Wabco accumulator is available for around £100 on e.bay, but be prepared to do some thread mods.

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I have a cross reference of JLM1907 for the Jag, or 25528382 and 88927271 in the GM parts catalogues (for the accumulator).

I don't know why the cross-ref list by Alan Swindon doesn't appear in my searches, :( but another one to bookmark is

http://www.drhess.net/crystal_princess.htm#Parts Substitutions

 

Also, I have attached documents regards repair/cleaning of the pressure switch.  The one marked Mod has info on the use of other switches that can make the system usable if cleaning doesn't succeed. Let me know if the pictures work....seem to have lost them when converting to Word 2016. :cry:

       
     

abs pressure switch repair.doc

ABS_Brake Switch Mod.doc

Edited by CarBuff
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Welcome to TLF Saqib. :welcome:

I bought a replacement accumulator for my brakes. As the other guys have said. Not expensive. Have a look in here and you will find a lot of information.

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Many thanks for all the suggestions.

CarBuff - the pictures were all blank any chance you could send me the unconverted Word files?

Looking around it seems the Jag JLM1907 is available but at the same price as the one advertised by SJ Sports Cars i.e around £230. The GM part numbers seem hard to find availability for even on the US sites. The Range rover P38 accumulator is cheaper at around £115 but it seems some connection modification is needed as there is no recess for the O-ring to sit in. Other than this there don't seem to be any other recent posts pointing to cheaper alternatives I can find  - please correct me if I am wrong or someone knows of a more reasonable source.

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This is what I used. https://www.ebay.com.au/itm/RANGE-ROVER-P38-WABCO-ABS-BRAKE-PRESSURE-ACCUMULATOR-STC2784/292375052989?hash=item4412e942bd:g:IMgAAOSwK6RZNnao

I recently did a post about my overhaul and decided to keep the Delco system as it's working properly now.

I recommend you go by the diagnostic result first and replace the bulb. All I did was to replace the "o" ring with one of thicker section. It screws straight on. Leave the ABS switch alone especially if road tests demonstrate it to be working. 

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Ahh, the ol' S4 Abs flashing light issue.

My ABS light would start to flash on every tenth run or so.  Very intermittent to start with.  After a year or so became more prevalent, to a point that is was on every run after a few initial pumps.

I changed the cheapest and easiest part to obtain first - pressure switch. Still had the issue. 

Sourced a new Lotus accumulator from SJ's late last year and replaced. Problem solved.

Reading more into it the accumulator is only designed to last for a set period of time (around 10 years).  I've now gone through two accumulators in just over 15 years.

Ease of changing (numpty rating): Pressure switch 6.5/10  Accumulator 8.5/10

I'd change the accumulator first.

 

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Thanks all

I will change accumulator first, clean pressure switch if that does not work and then panic after that.

Do I need to bleed the brakes after changing the accumulator (I know I need to depressurise first)?

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They're on different systems on the S4.  Brakes are on a separate line. The Switch and Accumulator are self bleeding I thought I read somewhere in the manual.  Anyway no issues when I replaced mine.

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No, they're not on different systems, they're connected.

Check section JF page 63 in the Service Notes.

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This is how it starts I’m afraid. Many of us (across several posts) have lost our battles with the dreaded Delco Moraine III system. It starts with the odd flash. Then the flash becomes all the time. Then the flash goes steady. Then yes I replace what you can: accumulator- I spent £200 on an Australian switch setup. It all works for a while and the problem shifts. It ends up as mine did with unreliable braking. Sometimes nothing sometimes everything. It’s scary. My Lotus is in storage because of this. I am hoping to acquire the replacement bracket system and get an independent specialist to fit it. I’ve rarely seen a happy ending with these awful braking systems unless they’re replaced with an alternative. 

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What happened in the end Saqib?

Everyone likes an end to a post - pressure switch cleaned/replaced?.

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It’s currently in storage as it’s unusable. There is however a solution in the offing. 

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