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Discussion Starter #1 (Edited)
As you may or may not know in most cases when the glow plug light flashes on your dash board (when driving!) its something to do with the brake lights or related electrical system.

The ideal when the glow plug light flashes (now to be refereed to as GPLF) is to connect to a VAG COM as what is actually happening is your ECU is telling you that there is a fault, GPLF it can be indicative of many things so connection to a VAG COM will let you know what it is for sure.

However........... As I said its normally something to do with the brake lights!

LED lights / modified bulbs

These will in most cases cause GPLF as the resistance of the bulbs is lower and thus the ECU thinks the light bulbs have blown, cure this instance of GPLF problem by use of of a MIL defeat loom.

At the time of writing both Brickwerks and T4'sR US sell them

First checks

Item number one to check, is are the lights going on and off?

- If so and only one bulb is operating then change it this should fix the GPLF.

- If so and both lights are working then you either have an intermittent fault with the switch (in which case attempt overhauling switch, as below) or you have another problem (in which case connect to VAG COM)

If the brake lights are not working at all then do the following in order:

1/ check both bulbs are not blown.

2/ check fuse number 20 (for brake lights) in the internal fuse box.

3/ overhaul switch

Overhauling switch

This took me 10 mins and saved a trip to the parts supplier, it is the easiest job in the world A:.

First of all remove the switch it is on a bracket above the brake pedal (note this switch is different to the clutch one which is a two pin). The switch has a plunger and 4 pins (the key is its above the brake pedal LOL:) mine was black in colour but I understand this is not always the case.

By hand twist the switch till it is free of the bracket. Then disconnect the plug. Pictures of the top of the switch, bracket and plug below for reference.







Pop the top off the switch which is retained by three clips you will be met with the below photo once fully dismantled



You will note that the switch is purely mechanical i.e. only moving components that make or brake two sets contacts thus this switch can easily be repaired.

Clean all the contacts to bright metal with contact cleaner and wire wool and reassemble the switch there are two sets (four) contacts to clean which are detailed below.

Picture of internal contacts you will need a small screw driver to put the wool on! (the one at the top of the screen had some crud in it which was my problem)



The other side of these prongs (1st pic) get hit by the other contact seen in 2nd pic (its the thin piece at just under the larger spring). The internal contacts get hit by the contacts under the bottom plate in the 2nd picture.





You can test the switch if you like by laying a multi meter on its most sensitive setting across first the two outer pins and secondly the two inner pins. The resistance should change instantly from 1 to 0 or 0 to 1 depending on which way you are going.

Then replace switch and job done.

Note if the switch is totally fried you'll need a new one GSF and VW sell 'em however this must be rare (if one has the part numbers to hand please add them in the thread or PM me).

Think this only applies to 2.5 Tdi engines but will stand corrected and edit as required :ILU:
 

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I think the part number is:
1J0 945 511 B, 1J0 945 511 C and 1J0 945 511 D

I had a bit of a problem with the GSF one, had to bin it and get a OE one from TPS. They do only cost about £7 though.
 

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I have noticed I can't spell
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Discussion Starter #3
Cheers Jimbo I am thinking about making this one a sticky :ILU:

The question gets asked so many times 'why is my glow plug light flashing' (think you asked it on the Bricky a little while back? even)

Know the switch is cheap but with that little write up in under 10 mins its diagnosed and fixed T: and unless you live right next to TPS or GFS has got to be above anything quicker :)

Also helps pin it down to if you need a VAG COM connection for free. I do have a VAG COM and in the time it took the laptop to power up I had the switch out and tested so no need this time :D
 

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Hmm, from the pictures I think the switch you've got is

IJ0 945 511 A

as it's fairly simple internally & doesn't appear to have the ractcheting plunger (from what I can see).

the later ones, as mentioned above have a suffix of B, C or D and have the ratcheting plunger which requires a little care with fitting/removing the switch to avoid breaking it.
An earlier thread:-

http://www.vwt4forum.co.uk/showthread.php?t=95205&highlight=brake+light+switch

mentions this &, in post 40 on that thread, I posted a link to another site where the whole procedure is outlined in pictures.

The GSF equivalent switch number is 931VG040401, I think.

Will check it tomorrow as I need to go & buy one :(
 

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I have noticed I can't spell
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Discussion Starter #5 (Edited)
The one in the photos does have a ratcheting plunger and I have done this with later VW and other VAG brake light switches its simple try it :)

Its off a 2003 van!
 

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Yeah, you're right, it does have a ratcheting plunger but not the locking mechanism on the later switches. Bad wording on my part.
 

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Discussion Starter #7
On a golf I had you had to be more careful installing the switch as it had this daft locking jobby for the ratchet.

This post is in the T4 section though and I am fairly that this is the switch used on 2.5Tdi T4's so all present and correct for subject matter :ILU: The only worry is if the switch is discontinued and the replacement part is version B C or D so if I make it a sticky it I will add notes to explain this :ILU: Cheers for the pointers.
 

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The GSF equivalent switch number is 931VG040401, I think.

Will check it tomorrow as I need to go & buy one :(

The number on their computer said 931VG0400 "Brake light switch 4 pin". The other number is probably just their online/ebay part number

The switch "the green one" also has some kind of locking collar that is locked when you fit & turn the switch in the bracket.

The only problem is that the plunger was too short to work in my T4. ( unless there's some way of adjusting the pedal, but then it'd be higher :-( ).

Ah well, it's booked in for a diagnostic on monday. Fingers crossed.
 

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I've got two 2-pin switches on my brake pedal (and one on the clutch)

All my glowplug light problms were solved with a bit of 'resetting' and 'putting the chuffing switches where they should have been in the first place'. Thanks to Trev (windwelder) back in the spring for sorting out that mess when he did my pedal box.T:

Will try to remember what goes where and post it up for any 99 'velle owners out there!

Great how-to thoughT:T:T:
 

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The number on their computer said 931VG0400 "Brake light switch 4 pin". The other number is probably just their online/ebay part number

The switch "the green one" also has some kind of locking collar that is locked when you fit & turn the switch in the bracket.

The only problem is that the plunger was too short to work in my T4. ( unless there's some way of adjusting the pedal, but then it'd be higher :-( ).

Ah well, it's booked in for a diagnostic on monday. Fingers crossed.
Would you believe it, after all I tried - cleaning switch, changing bulbs etc ,- it was STILL the brake light switch/circuit!!!!!

Two other common faults were recorded but weren't causing the ECU any real anxiety.

17656 Start of injection timing regulation: control deviation: P1238 -35-10 - intermittent.

17653 Needle lift sensor (G80): short to ground:p1245 -35-10 - intermittent.

What do the P numbers mean exactly? How recently would the fault have had to occur? Any "Cage mod" type procedures worth doing for these last two faults?

I'll have to get clued up on these things, once my vagcom cable arrives.

BTW: Anyone want a GSF Green brake light switch?
 

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Could be old codes. Best to Wipe em then see if they re-occur.

If they come back--

With those codes it could just be your 5th injector or wiring.

Could be injector and pump timing out.
 

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Thanks Everybody, particularly Edbluejuice for that excellent information. Even a luddite like myself should be able to have a reasonable stab at that now. I do appreciate the time and effort taken in answering what has been asked before.

And yes, in future I shall do a search first. Only just beginning to realise how amazing this site is.

Thanks again.

Steve
 

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Oh Bum!!!!

Yesterday, on the way home from our first dive trip in the van, the blooming light came back on!

Mackenzies have said to bring it back in for another diagnostic run.
 

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..and this time it was the needle lift sensor fault.

Mackenzies cleaned everything up, put it back together & ran it and everything is OK..........for now.

It might be the usual glitch, or it might be time for new injectors.

We'll just keep our fingers crossed & see if it comes on again.

Bearing in mind that if CmC don't come up wih the requested service history soon, we'll also be looking at a service & cambelt/water pump replacement as well.

These things really are money pits, aren't they?
 

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Blimey, I've just folowed this to the picture and my brake lights are working and the glow plug light has gone out :DA::DA:

This has literally taken me 10 minutes and I can't believe it.

Just a point of note, my brake sensor had 2 pins rather than 4. The front of the black housing unit came off easily along with a spring, it wasn't possible to get the connectors free to give them a clean. I had to do a bit of jiggling and run a thin scredriver down the length of the connectors and scrape off what crud I could. Worked though T:
 

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Having problems with my brake lights not working, i took the switch out as described (brilliant write up by the OP T: ) but unfortunately found the little square raised contact patch that you can see in the picture has 'worn/burned' away on one of the contacts so just ordered a new one

2 Min's later VW ring me back, the part ordered has been modified, so it looks like i will be getting one of the newer type switches :( that aren't as robust. will let you know how i go on ;)
 

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well i collected the switch this morning. it is a modified part now, and apparently the only choice for ordering at the stealer's ? i got it out and took a pic for you.

[/IMG]


the green one is the new part and after reading beforehand they were to short i couldn't see how it would work myself. you can clearly see the plunger is 10mm shorter than the one i took off the van :* (the pen line running through is where they sit in the bracket.

well i fitted it, and it didn't reach the pedal :confused: also the plunger was stiff once the switch was turned/locked into the bracket :confused: i took it out/refitted it a few times then got it working A: tbh i don't know how exactly apart from it seemed to start working when i turned it back slightly :* but the main thing is it is working T:

hope this might help somebody.

also this link is helpful, look halfway down the page.
http://forums.vwvortex.com/showthread.php?1158315-DIY-Installing-a-new-brake-light-switch-(without-breaking-it!)/page9
 

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Did this how to......and found 1 of my contacts all black,cleaned it put back together and bingo brake lights on once more.T:T:T:
 
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