IknowHuhA6

Wanted to share my latest DIY fix in case it helps anybody from an expensive trip to Dealer. I thought it was a bad sensor, but apparently not.

I've been having open hood warning light for past couple days. I opened hood and closed it and all was fine on first few days.
Few days later I'd open and close hood and now problem wasn't going away anymore. So I started researching. Seems the C7 A6 has three hood latches. Center/driver side/passenger side. The latches at each end have sensors. So here are the adjustments possible

1. There is a rubber bumper stop at top of hood on each side that can be rotated to lengthen or shorten bumper height (but leave this alone if you're inexperienced as you could end up with hood rattle). I removed mine completely and used play-doh to measure gap size when hood closed and reinstalled these to correct height.
2. There is also adjustment to hood catch bar at each end of hood using a star socket. (Pic 2 & 3)
3. Pic 3 shows the hood latch (yellow arrow) on each side of car and has two 10mm bolts on inside (red circles) which hold it in place, but this unit can slide up and down for adjustments if you loosen the bolts. The hood latch has a sensor (green circle/ellipse/whatever) to tell if the hood is latched or unlatched (hence the hood open warning).

Since I work on my car alot and frequently open and close hood, I guess the slamming down of hood kept pushing the hood latch down by minuscule amounts until it was finally too low to latch the catch bar, hence causing my problem.

Since this was my first time with this problem, I went to mistakenly adjust hood bumpers first. I ended up with hood rattle, hood no longer aligned with fender and no fix.
I then went to adjust hood catch bar and seemed to get closer to fix.
Last I loosened hood latch and pushed it back up. This with combination of readjusting hood catch bar and bumpers finally got the problem fixed.

So if you get this malfunction, try the hood latch FIRST before screwing up the height of bumper and hood catch bar as these are less likely to be the culprit.

Lesson learned, STOP slamming the hood! And push it down to close.

Warning, if you try this yourself and don't succeed in getting hood to latch, you will see hood bounce up and down at corner where the problem is as it is not latched correctly at highway speeds above 50mph. So test, redo, test, redo. I'ts a process but worth it for safety and bit of savings. There are still two other latches holding, but I prefer to be safe. If you don't have patience just take it to dealer.

schalliol

Nice write up! It sure seems your work could save others here a lot of time and maybe even safety risk

IknowHuhA6

Thank You! It's positive comments like yours that inspire me to keep posting helpful threads to try and help others. I remember a time when not having a clue and needing help so just trying to pay it forward.

Thank you for your appreciation.

Bartenderfloyd

Excellent write up. I love to hear from other DIYers. Thank you.

clay.snyder

I'll be trying this tonight! Thank you!

IknowHuhA6

To identify the offending latch, i disconnected pigtail on sensor one at a time. Mine was driver side. The open hood warning went away when disconnected it.

Make sure you tighten well. I had to redo and retighten since apparently bolt gets alot of downward force exherted on it.

Hope it helps.

ronrevere

I have the same light on for a few days now. I'm gonna try later today. After I figure out why my wipers aren't working all of a sudden.

IknowHuhA6

Probably easier than strike latch itself, is to use star socket to slightly lower the hood latch bar above. If lower strike latch krept down, make sure bolts are nice and tight so doesnt keep shifting down.
There is also possibility sensor wire went bad.

go9093

I have similar problem with hood sensors - A6 C7. After cca. 30min of driving I start to see this "hood opened" notification on dash board. And it is just flashing - not constant - and my windscreen wiper work normally. I've tried to disconnect the left sensor. I should try to remove the right one as well but having trouble since it is not easily reachable. YouTube video or manual how to remove / disconnect right sensor would be nice.

Video of notification that I see while driving:
https://goo.gl/photos/FEqSSvUsu2zsKTVa6

IknowHuhA6

Sensor disconnects easily with a pick tool. Can't remember if you push down or pull up on the securing tab but both left and right are removed same way.
When hood open indicator turns on, pull up on the closed hood at each latch location to see if hood pulls up slightly (meaning not latched). That's the side that will need to be adjusted.
If the hood does not pull up slightly and is locked firmly into place at each corner, they it may be a failed sensor.

When I had this problem, I would press down over latch and it would lock with the added pressure. Once I had the time, I used the star socket to adjust the upper strike distance at underside of hood.