Glow Plug Warning Light

[neil]

The blasted light is flashing again only 1 month after fitting a new brake switch and a new blue switch that is fitted underneath the black one.

The fault only occurs after a reasonable cruising time without touching the brakes, putting the brakes on 'resets' the warning light for a short period.

Cannot keep changing the switch every few months, even if they don't cost the earth.

I have read all the previous posts on the subject but can someone offer some advanced help ? How can I test the switches to find which one is at fault (apart from disconnecting one at a time), is there something else I should be looking at ?

Does anyone know exactly what the second blue brake switch is for ? Have seen various theories about ABS, cruise control etc but nothing definate.

Vehical is a 97 1.9TDI Ghia without cruise control.

 

Cheers : :(

[Topbloke]

Black switch is for the brake lights and also sends a signal to the ecu . Blue switch is for the ecu, they should both work in unison, worth checking that they both work together may be okay when car interior cool but one could be closer to heat vent possible distotion in bracket they do sufer from poor connections also . If one off the brake light bulbs fails it will also make the light flash could be poor connection at the rear lights or dodgy bulb ie fillament touching some times other times not .just another thought are you an aa member if so give them a call we have laptops which can access some ecu's, engine only but worth a try. they also have a tech department that you can call . I am assuming that the vehicle is a manual it has a switch on the clutch pedal as well worth checking this also for the afore mentioned problems :(

[neil]

:( Thanks Topbloke

 

Yes it does have a switch on the clutch pedal, would this cause the GP warning light as well as the brake switches?

 

My vehicle also has a 'light out' display on the dash, if this isn't showing a fault at the same time as the GP would this discount the faulty bulb theory ?

 

Can you test the switches ?

 

Also the 2 wire connector to the blue switch on the brake side can be fitted either way round, does it matter ?

[Topbloke]

the switch on the clutch pedal is connected to the ecu and tells the cruise to disengage not to sure if faulty switch would make light flash but you could disconect it and see what happens worst it could do would be that the cruise would not work.

 

i would expect the light out tell tale would inform you, did not know what spec you had but applying logic it must be full spec to have cruise.

 

you can test the switches,you would need two multi meters and connect them to each switch set to resistance then press pedal should both work at same time, you could do it with some wire's and bulb's and holder's and some power but would be hard work. if you did it with one meter you could see that they worked but not in unison.

 

blue switch is purely on/off and makes no difference which way .

 

why are you so sure that the flashing bulb is to do with the cruise ?

[Topbloke]

forget the last question, long day and on earlys. :(

[neil]

Topbloke, we seem to have our crossed wires here.

 

My vehicle doesn't have cruise fitted and i don't think that this is anything to do with the problem.

 

Thinking about it, the brake switches must work because the GP warning resets as soon as you touch the brakes.

 

What faults does the flashing GP symbol cover ?

[Topbloke]

as far as i am aware it covers the glow plug cicuit and acts as the engine management warning light, apologies for the crossed wires see last post I think what happens is that when you press the brake pedal it turns the lights on (der) an tells the ecu that you are braking which shuts of fuel and tells it to disregard boost presures etc . I also drive a t4 veedub and that shuts fuel of cos if i press accelerator and brake at same time it don't rev up (have large feet) same sort of idea keep me posted going bye bye's now :(

[Guest barney]

Well I am so glad I read this thread as I too had the same problem with the flashing Glowplug light. My problem appeared when the brake light foot switch was renewed, i just could not figure out what was wrong and Ive lived with it for months.

Anyway today I rechecked the blue brake switch and adjusted the switch and problem has cleared. Its really useful this site.

 

By the way My Mercedes MAF sensor is still running ok , thats 1 month since I installed it .

[neil]

Barney, what did you find wrong with the blue switch, and how did you know it was this one at fault and not the black one ?

[neil]

Still looking for advice, any other helpers ? :P

[Ivor_E_Tower]

Reset the switch- even a new one when you have fitted it. Try searching for how to do this (sorry cannot remember off hand how it is done, but it is very simple). I take it you are still having problems with the GP light?