Random hazards solved - probably

Crikeymikey

A2OC Donor
SHORT VERSION

Faulty hazard relay. 8Z0 941 509 B. Fixed for £20 (used).

LONG VERSION

Hazards were going off intermittently earlier this year, without any obvious pattern of behaviour. Never whilst driving. Ambient temperatures did not seem to be a factor but I suspected a dry joint on a pcb somewhere to be villain of the peace, one way or another.
The problem would always cancel from the hazard button on the dash.
Diagnostics (I use an OBDelevenPro) suggested that there wasn't an external source (petrol cap, interior monitoring, boot lid, etc) causing the trigger. Additionally no fault codes were being logged.
Searching here on the forum I discovered this is a common problem, often leading to suggestions that the CCCU was the likely culprit but rarely was such speculation confirmed with a successful replacement and fix.
Fearing the worst, I decided to go down the easiest path and first replace the hazard switch (thanks @ICowie ). This made no difference and the hazards continued to go off randomly every few days. I did take the opportunity to clean a sticky cup holder so not a complete waste of time.
Next easiest to replace, I figured the hazard relay could be the cause. Thanks to @A2Steve for that item. I took this opportunity to do the Comfort Blinker mod.
It has been 4 weeks now and despite varying temperatures and conditions the hazards are behaving themselves.
So not a John Grisham worthy outcome, but a result none the less.
Thanks again to Iain and Steve, and thanks to you for reading this nonesense. :)
 
Last edited:
SHORT VERSION

Faulty hazard relay. Fixed for £20

LONG VERSION

Hazards were going off intermittently earlier this year, without any obvious pattern of behaviour. Never whilst driving. Ambient temperatures did not seem to be a factor but I suspected a dry joint on a pcb somewhere to be villain of the peace, one way or another.
The problem would always cancel from the hazard button on the dash.
Diagnostics (I use an OBDelevenPro) suggested that there wasn't an external source (petrol cap, interior monitoring, boot lid, etc) causing the trigger. Additionally no fault codes were being logged.
Searching here on the forum I discovered this is a common problem, often leading to suggestions that the CCCU was the likely culprit but rarely was such speculation confirmed with a successful replacement and fix.
Fearing the worst, I decided to go down the easiest path and first replace the hazard switch (thanks @ICowie ). This made no difference and the hazards continued to go off randomly every few days. I did take the opportunity to clean a sticky cup holder so not a complete waste of time.
Next easiest to replace, I figured the hazard relay could be the cause. Thanks to @A2Steve for that item. I took this opportunity to do the Comfort Blinker mod.
It has been 4 weeks now and despite varying temperatures and conditions the hazards are behaving themselves.
So not a John Grisham worthy outcome, but a result none the less.
Thanks again to Iain and Steve, and thanks to you for reading this nonesense. :)

Hi Crikeymikey, is this the relay you're talking about ... I've had the same outcome as yourself with the hazards now behaving as they should after soldering in a new one 👍

 
Last edited:
Hi Crikeymikey, is this the relay you're talking about ... I've had the same outcome as yourself with the hazards now behaving as they should after soldering in a new one 👍

That's it. 8Z0 941 509 B
I replaced the whole thing rather than fiddle about desoldering the sub-relay, etc.
I went on holiday a while ago and had to disconnect the battery while the car was at the airport. What a faff that was!
 
That's it. 8Z0 941 509 B
I replaced the whole thing rather than fiddle about desoldering the sub-relay, etc.
I went on holiday a while ago and had to disconnect the battery while the car was at the airport. What a faff that was!
Mines been behaving since the fix, a couple of months now ... last time left at the airport I just pulled the fuse, I think it's number 34 from memory ... if it starts doing it again I'll bite the bullet and buy a new one from the dealers as the last one was fine for a good seventeen years or so 😆
 
At least it's not the alarm going off as well, like some poor souls! Predictably, it's electrical gremlins more than any other that provide the challenges of owning a "modern classic".
I've had my TT for 15 years (it's a 2002 though) and the only non-wear and tear issue I've had was the alarm siren packing up after a few years. A simple fix for the practical of mind and one that I applied to the A2 as soon as I got it a year ago.
Fuse 34, eh? I'll make a note of that. :)
 
Back
Top