Bonnet latch sensor - Alfa Romeo Forum
You are currently unregistered, register for more features.    
Thread Tools Search this Thread
Status: - Update
Posts: n/a
Bonnet latch sensor

Have a funny one...

Had the bonnet open last week while changing front pipes - now when I close the bonnet the indicator light on the dsh comes on to say the bonnet is open. When I open the bonnet the light goes out.

Nothing has changed and wiring is all correct.

Anyone any clues?? Cant use the remote locking as it turns the alarm on - which then goes off every two minutes because it thinks the bonnet is open.

Cheers all
Sponsored Links
Status: Occasionally driving my Gtv
Club Member
Membro Medio
alexGS's Avatar
Club Member Number: 1265
Join Date: Jul 2007
Location: New Zealand
County: Waikato
Posts: 2,361
Images: 36

Member car:

Gtv V6

It's a strange one, but I reckon what you really have is a faulty microswitch. I replaced mine recently - it's a standard (mini) size. Microswitches come in three sizes - full size (two diagonally-opposed mounting holes, two terminals on the back, one underneath), the miniature size which is the one you need (two side-by-side mounting holes, three terminals sticking out the bottom), and subminiature (similar but very small). Here's a link to the type you need (one with a lever) Miniature Microswitch : Micro Switches : Maplin

The bracket is attached by three bolts accessible once the left headlight is removed. The microswitch is held into the plastic bracket by two aluminium rivets - drill off the heads, they are still a tight push fit and can be reused. You'll need to solder the wires to the new switch - don't worry if it looks a little different - be sure to use the NO (normally-open) and C (common) terminals - the lever in the bracket opens the switch when the bonnet is shut, reversing the logic.

The original microswitch is some exotic high-quality sealed version that is probably designed to give false landing gear warnings on aircraft but is just as capable of giving false bonnet-open warnings in cars.


'00 GTV V6, '08 FIAT 500, shell and parts for a '71 FIAT 850 Coupe
alexGS is offline  
Status: - Update
Posts: n/a
Cheers for that. Worth changing as its driving me nuts. Although it will be a pain in the bum getting the headlight off as the fixings are all seized solid.
Status: And on the eighth day God made Alfas..!
AO Gold Member
pendragonfalls's Avatar
Join Date: Feb 2010
Location: Ireland
County: Carlow
Posts: 6,590
Images: 20
The boot warning in my 166 does it sometimes. Comes on for a few days and goes off again. Its got a mind of its own. I've stopped worrying about it now.. :mygrin1:
pendragonfalls is offline  
Status: Constantly Nagging Lincolnshire Members !
Regional Support
For Lincolnshire - AOL
Nige005's Avatar
Join Date: Jan 2008
Location: Boston, Lincs
Posts: 16,082
Images: 22
Originally Posted by pendragonfalls View Post
The boot warning in my 166 does it sometimes. Comes on for a few days and goes off again. Its got a mind of its own. I've stopped worrying about it now..:mygrin1:
Usually happens in Winter during damp conditions. Had this on my TS GTV last Winter but as the Switch is built into the Lock I left it alone, we'll see what Winter brings.......

As for the Bonnet Switch - what Alex said.
Nige005 is offline  
Status: - Update
Posts: n/a
I might try and surprise it and swap the wires round!

If i sneak up on it then its bound to work
Status: -
AO Member
alfa pint's Avatar
Join Date: Feb 2007
Location: United Kingdom
County: Argyll and Bute
Posts: 71
I had this problem last year when it was wet, but then it went away of its own accord (not the first time in my Alfa!).

However, this time it looked pretty terminal - no amount of drying the car out turned the light off and I had the same problem viz the alarm going off. Guidance from this forum, although another post, suggested that just removing the switch altogether would solve the problem. Took me about half an hour tops, most of which was trying to clean the switch and the contact to get it to work properly, but the fault was with the connector slightly further back. Removed switch altogether, insulated the end of the connection and now the remote central locking and alarm work perfectly fine! I can tell visually if the bonnet's open.

Drink makes you think. Food makes you fatk.
alfa pint is offline  
Status: - Update
Posts: n/a
I cant do anything with it at the minute as I cant get the headlight off to gain access.
I currently just lock the car with the key rather than the fob - so no alarm
Status: Forever MG sorry Alfa you were fun though
AO Member
JimmyCoupe's Avatar
Join Date: Oct 2011
Location: United Kingdom
County: Kent
Posts: 236
I totally know how you feel mine also does it. Thank god for the locking with the key work around otherwise the neighbourhood would totally hate me.
JimmyCoupe is offline  

Go Back   Alfa Romeo Forum > Supported Alfa Romeo Models > Technical & Vehicle Assistance > Alfa GTV & 916 Spider

bonnet , latch , sensor

Thread Tools Search this Thread
Show Printable Version Show Printable Version
Email this Page Email this Page
Search this Thread:

Advanced Search

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

For the best viewing experience please update your browser to Google Chrome