HAZARD SWITCH FLASHER UNIT FIX - HOW TO

My indicators stopped working coming home tonight and I had to flash the indicators manually... then it started working again! Fortunately I'd seen an excellent post recently. Feeling inspired by XTR's excellent pictures of his switch internals http://www.tt-forum.co.uk/ttforumbbs/vi ... 943#809943, I decided to take the unit apart to clean the relay contacts.

Radio and switch removal

First you need to take out the radio and then the switch. Follow this guide to remove and replace the flasher switch module: Flasher Removal

I found that my radio was difficult to remove with the Audi OEM keys. (Wak has a picture with the part number: Radio Keys)

Inserting the keys sounded like they were scratching around without doing much. I have two sets and I did find that inserting two sets at once helped as it fills up the slots and is more solid. I found that the metal in the radio clip supports was bent. I straightened them with pliars and now the radio comes out easily with one set of keys.
Repair procedure:

Once you have the switch out you need to mark the top of each part with a felt pen or similar in order to get it together correctly. Carefully prise off the red cap and push out the locking bar:



Then prise up the sides of the case just under the locking bar and pull the connector. The PCB should slide out but don't force it as the LED stem will catch on things! You can see and guide it having removed the button.



There are two springs to catch so be careful not to loose them



There are two contacts for the hazard lights and one set of contacts for the indicators. The indicator contacts are shown here:



They were burnt and pitted and had welded themselves together at some stage. What happens is that the sparking causes oxides and carbon to build up and raise the contact resistance. The increased resistance causes heat and more arcing which eventually welds the contacts together. It needs to be prised apart if welded and cleaned.

A little piece of fine glass paper (not wet+dry as that's conductive) slipped between the contacts and rubbed backwards and forwards, whilst applying a little manual closing pressure, usually cleans up such contact nicely. Unfortunately there's not much room to do that. What I did manage was to poke a fine Jewlers screwdriver in between the contacts in order to scrape them clean and get back to shiney metal.

Make sure you don't bend the contacts. If you press the magnetic actuator down, the contact should close slightly before the actuator reaches its stop - that way you ensure some contact force when it closes. Make sure the contact opens with sufficient gap however. If the contacts were eaten away or you bent them too far open, the force will have lessened and you'll get poor resistance. Too small a gap and they may arc and not break contact properly. You probably won't need to clean the hazard contacts as they won't have been used much. In fact, they can be used as a guide to assess the correct contact gap and closing pressure of the cleaned and refurbished contacts

Give all three contact sets a spray of contact cleaner such as this Servisol Super 10. This will lubricate and keep the contact resistance low - it's remarkable stuff. You can get it from Maplins etc.



The cleaned contacts will hopefully last for a long time but it depends how badly eaten way they are. The best option would be to replace the relay. Here's a possibility but I have not checked the size - it may be too big as the Audi ones are small. It's a changeover relay but the second pole is unused in this application. (Unfortunately it's now no longer stocked at Farnell)


http://uk.farnell.com/jsp/endecaSearch/ ... SKU=176587

Note: Audi's supplier has revised the switch design. It's fit and function identical but just slightly different internals. It'll be the relays becoming obsolete that's driven this change.

Still, same principals apply but the contacts are difficult to get to as the relays are shrouded. Here are the data sheets for those two relays:

http://omronauto.com/PDF/G8N-1d_data.pdf
http://omronauto.com/PDF/G8NW-2e_data.pdf

The first one is for the single pole changeover - the smaller one of the two and the one that flashes the indicators.

With these, and as you've got nothing to loose, you can try cutting away the plastic case of the relay - it's only a thin protective cover. If you cut around the top (file off the edges) you should be able to pull the lid off as it where and see inside. Don't cut too deep for fear of damaging the coil. Then do the side edges (bending the sides down and breaking away) and you'll expose the insides, which should look similar in principal to the original open frame design. If you have a soldering iron you will find it easier with the relay removed from the PCB.

Clean up the contacts in the same way as with the original.

Alternatively you could buy a new relay from Omron or a distributor. I tried Farnell and RS components and they don't stock them but there are other suppliers. Omron may provide a free sample to an enquiry if you're lucky http://omronauto.com/.

Unfortunately the PCB has also been revised to accomodate the new relays, so you can't easily simply replace old relays with the later types without modifying the PCB - and I'm not sure if there's overall room.

Reassembly:

Getting it back together is a little tricky. You need to take the sliding button apart further. Some careful prising is needed. Make sure you mark orientation of the parts. Then assemble the springs in their holes and locate them onto the pegs of the slide and click it together with the PCB assembly.



Next carefully slide the PCB assembly into the body making sure the PCB slots into the guides inside the body. It should lock into place. You can slide the locking bar back in at this stage.

You can now replace the round piece of the button slide. Make sure the single tag for the red cap is on the label side of the switch body (highlighted).



Now you can snap the red button back on and replace the unit in the car. I'm pleased to report mine works fine now

N.B. Apparently there have been some cases of the indicator stalk being faulty and causing a similar problem. Differences between left and right indication with one being faulty and the other not would tend to indicate ( ) the stalk was at fault.

If your flasher unit is beyond repair the Audi part number is P/N 8N0 941 509

nice write up..... John.

I always wondered if it was contacts wearing or the relays being close that one magnetised the other.

Problem solved....

Nice one again John, didn't have to get to cold and dirty on this one .

Gtear write up John get it added to the FAQ at the top of page one m8

you're unbeleiveably good at this ..

nice write up ..

Great write-up John. Re-assuring to know this sort of detail is available if I ever have this problem with my TT. This is such a fantastic forum!

Excellent write up. However it has not worked for me, my indicators dont work at all but my hazards do, what does anyone suggest this could be??

What are the symptoms? Can you hear the relay clicking with the indicators? Do the lights come on with the indiicator stalk?

If the lights come on but they don't flash (no clicking) I'd suggest your contacts may be welded together or don't separate far enough when the relay is not energised.

If the relay goes click but the lights don't flash, I think you may have bent the contacts too far apart, so they don't actually meet when the relay is energised.

Other faults may be something else like fuses, blown bulbs, bad connections, or even the flasher circuit board or relay failed etc.

Thanks for the reply it flashes once but I cant hear a click after that if i flash them manually they work? Will i need to buy a replacedment unit? I have been told they cost £27 is this the correct symtom in your opinion??

With just the ignition on, push the indicator stalk up but not so much that the lever clunks into the fully on position - but enough to turn on the indicators (this is just to achieve quietness )

Listen to the indicator flasher. If it makes one click so the lights lit up briefly then go out (in the normal period) but then they don't light up again anymore, so you have to manually flash them by hand - then I'd think the oscillator has stopped oscillating. Possibly a component was damaged. You could check any dodgey looking solder joints but you might just have to get a replacement if you can't see what's wrong or dont have the repair equipment. Sorry

I'm not sure about the price. I'll check later.

I have just done this fix and it works

Saved me buying a new unit

Took about 30 mins to take the unit out and then clean the conectors and replace.

BE WARNED

You need special key to remove the Head Unit, so a quick pop to the dealership and ask the nice Service Man to remove it.


Good luck

OK job done but how the feck do you get the radio removal keys to release from the radio. I have put a bit of force in trying to remove/pull them out but dont want to be too heavy handed. Do I just give em a hard Yank I dont want to break anything

Wak wrote:

Thanks again Wak. That is the bit missing from John Hs write up. I will insist he amends it

Well i fixed mine to save myself £35 from the stealers!

about 3 weeks later it broke...... so ended up buying a new one!

Anyway

Hope yours works for longeer!