Brake Warning Light

[fjmuurling]

Hi Owen,

 

maybe it's an idea to hook up a pressure gauge?

[dodge1979]

Check the wiring to the low pressure switch. If the switch isnt wired right the light will show up even if everything is working correctly.

As for going through the mot with the abs disabled...just remove all four wheel sensors tidy the wiring up out of sight remove the two 10amp fuses next to the ecu. Remove the abs warning light bulb. No need to rem9ve ecu etc. If you have a friendly mot man just say the handbrake warning switch is playing up hence the brake warning light...theyll be fine. There is no physical indication that an abs system is fitted once tge above is removed...99% of testers wont have any experience with an esprit and its "quirky" master cylinder. .

Whilst this may not be to everyones preference it is true and works..

[andydclements]

Well, hoping it's still as it was, and that being everything working as it should with Owen's car now.

 

It appears the warning light pressure switch (aka low pressure switch) was out of calibration.

 

Having tried a few tests we checked to ascertain when it became a closed circuit/ open circuit and to my surprise, it closed at pretty much the moment the pump cut out. This indicates the pressure required to close it was the same as the pressure required to open the high pressure switch (aka pump switch). That's nowhere near correct as the low pressure should be operating at circa 1800 pis and the high pressure at circa 2700 psi. A quick adjustment of the screw that sets the switch was done, based on it operating at circa 20 pedal operations (40-50 to empty accumulator form 2700 psi) was then confirmed by pressuringsing the system from a depressurised system. The switch opened at approx 18 seconds, with the pump running for approx 40 seconds.

 

A quick trial on the road and all seems well.

 

The calibration issue may have been a mistake (set to the high pressure setting) or something may have altered in transit, either way, it was working when I left it the other night, so hopefully it works now and keeps working.

[Vanya]

Wait there's a screw on the stock ABS pressure switch for adjustment? This is news to me.

 

I've been having a weird brake warning light since I bought my car - used to have ABS blinking but that went away with the accumulator change, however the other light is still an issue. Certain days when I start the car, it'll disengage with the handbrake, but most of the time it just dims slightly and stays on.

 

I checked the handbrake microswitch and cleaned out with electronics fluid etc but to no avail. Next stop, pressure switch.....

[andydclements]

I should say, this is the after-market replacement for the switch, the OEM part is unavailable.

[Vanya]

Ok, figured as much, but now I'm confused: I'm aware there's an Australian made solution but to my knowledge that replacement lacks an output to the brake warning light - unless Owen has a seperate switch for the brake light in series with the pressure switch?

[andydclements]

It is the Australian kit. It comprises:

low pressure switch

High pressure switch

Banjo type take-off point (that slots around the next bit) with a take-off point for one of the switches.

Adapter/ extension that screws into original switch position and has an orifice for one of the new switches in the other end.

[Vanya]

Ok I think I may have my brake warning light narrowed down by now:

 

Espritmon/Freescan detect no errors in the brake circuit - ABS is ok, pressures are ok.

Handbrake switch also works fine.

 

I realized that a reformulation of my intermittent problem might be in order:

The brake warning light doesn't come on - it simply doesn't turn OFF once the engine is cranked. A relay in the front compartment ensures that the CEL/Oil light/brake light etc engage when the ignition is turned on to let the driver know the lamps work.

 

I've noticed that basically, all the lamps go off when the engine is started, except quite often the brake light simply stays on.

 

There is one contact on the Tell-Tale relay that governs the brake light, leading to a black and white wire attached to a spade connector on the car - I've tried checking the cable for loose contact by jiggling it about with the car on as well as spraying contact fluid, but no luck.

 

Is it possible that the relay has been damaged internally so that it no longer turns off the brake switch at all times? Could dirt have ended up on a pole inside the relay, or am I totally off the mark?

Edited July 21, 2013 by Vanya