Handbrake-on warning

[djgilson]

Here’s one even I can understand - no obscure electronics, no VCDS codes..........

The handbrake-on warning on my 5 year old A4 came on and wouldn’t go away, no matter what I did to the handbrake lever. (The audio warning is strident and hard to live with). I found I’d fallen victim to a poor piece of design on the switch mounting. The switch is operated by movement of the handbrake lever, but there’s a weakness which allows the switch to move out of engagement with the lever over time.

You can get at the switch through the rear ashtray aperture: Pull out the ashtray; remove the rear cross piece of trim by pressing retaining clips outwards; and remove the armrest if fitted (need 13mm ring spanner for the single nut). Before removing the armrest, unplug the connector for the armrest light. (No I didn’t know it had one, either).

At this stage, be sure to pack the space under the handbrake lever bracket with a cloth, to prevent small objects falling into the handbrake mechanism below...........

The switch mounting uses an expanding plastic prong (technical term) moulded into the switch housing and it’s this prong which is a bit feeble and distorts with time. I found the switch just needed a nudge to get it to work correctly.
A4HandbrakeSwitch 009.jpg

So, disconnect the wiring plug, persuade the prong out of engagement with the aid of pliers and a bit of cautious levering, and remove the switch. Cut off the plastic prong, find a suitable small nut and bolt (max thread dia 4mm), drill a 4mm hole where the prong was, and Bob’s your uncle.
A4HandbrakeSwitch 016.jpg

Here’s the switch back in place - the nut is just visible. Use Loctite on the nut to stop it unscrewing. And don’t forget to remove the cloth.
A4HandbrakeSwitch 019.jpg

Of course you could just buy a new switch, but that wouldn’t be as interesting, and you’d have to replace it again in 5 years time.

Anyone else experienced this fault, or am I just unlucky?

[djgilson]

No? It's just me then.

[gmf70]

Just encountered the same problem, and yes, the audio warning is quite annoying. Going to try to fix it myself with your post as guidance. I see that I can get a replacement switch for < $20 if the switch itself is bad.

[djgilson]

Welcome to the Forum. Be interesting to know if your problem proves to be the same one of plastic creep, and if so the mileage of your vehicle?

[gmf70]

After disconnecting the switch a couple weeks ago I finally had a chance to try your suggested fix. ~ 1 hr and $1.50 in miscellaneous hardware later my original warning switch is once again functioning properly. Much better than the $450 Audi wanted to replace the switch. I would have completed the repair quicker but I skipped the "be sure to pack the space under the handbrake lever bracket with a cloth" step so of course I dropped something in there that I had to fish out after removing additional brackets. Thanks for the helpful and detailed post. 83,000 mi.

[eti7]

I had the same problem on my 2010 Audi A3, where the red brake light would stay on with constant beeping and a message saying "Handbrake is applied" even though the handbrake was fully down... I too thought it would be the plastic switch under the handbrake but it was actually the sensor on top of the brake fluid reservoir, which moved out of place because of the car wash using their jet wash to clean the engine as part of their valet procedure!! The mechanic readjusted it back into place and the problem was gone immediately! So if you have this issue, it might be worth checking this sensor on top of the brake fluid reservoir first. Hope this helps!

[djgilson]

Thanks for your input. It reminded me to update the photos, which are no longer supported by Photobucket for free. Apologies to all.