Notices

Bonnet - hood - trunk light is not working - Not So Simple

 
Old 05-30-2013, 09:40 AM
  #1  
Aussie Alan 993
User
Thread Starter
 
Aussie Alan 993's Avatar
 
Join Date: Nov 2003
Location: Sydney Australia
Posts: 444
Likes: 0
Received 0 Likes on 0 Posts
Default Bonnet - hood - trunk light is not working - Not So Simple

What ever you prefer to call it, the light in the front bonnet of my 993 is not working.
Yes, I searched and only found some old threads with no solutions.
Of course, I checked the bulb and the holder, I also checked the wires have 12V until you put a bulb across them then it goes to 0V, I even put a LED festoon light and it glows very dim.
The engine lid light is good, so are the interior and glove box lights, the bonnet latch switch seems to work because the interior lights come on when you release the latch and the voltage on the wires goes from 12V to 0V when the latch is closed.
Is there some sort of module that controls this light, perhaps the one that controls the delay on the interior lights? Perhaps it is a bad ground, but where?
Thanks in advance for any ideas that help me nut this one out.

Cheers
Alan
Aussie Alan 993 is offline  
Old 05-30-2013, 11:55 AM
  #2  
hoggel
Addict
Rennlist Member
 
hoggel's Avatar
 
Join Date: Jan 2005
Location: SLC, Utah
Posts: 995
Likes: 0
Received 0 Likes on 0 Posts
Default

The 12v contact of the light should not go to 0V when the the bulb is in place, It should stay about 12V and the light should come on. You either have a bad ground that is not allowing enough current to illuminate the light or you have some high resistance between the fuse and the light that is limiting the current to the bulb.

[WRONG]Use a jumper from a 12V source (battery is right there) to one end of the bulb. Touch the other end of the bulb to the ground side bulb holder contact. Light? If yes, the problem is between the fuse and the 12V contact of the bulb holder. No light (and you know the bulb is good)? The problem is on the ground side. Pull the connector off the latch and jump the ground side pin to the opposite end of the light from the 12V. Light? If yes, the switch is not making good contact. No light? The problem is between the connector and ground.[/WRONG]

Last edited by hoggel; 06-01-2013 at 04:21 PM.
hoggel is offline  
Old 05-31-2013, 11:05 AM
  #3  
Aussie Alan 993
User
Thread Starter
 
Aussie Alan 993's Avatar
 
Join Date: Nov 2003
Location: Sydney Australia
Posts: 444
Likes: 0
Received 0 Likes on 0 Posts
Default

My best guess is a bad ground so I'll have to go looking. Any ideas where the most likely place to start?

AA993
Aussie Alan 993 is offline  
Old 06-01-2013, 04:20 PM
  #4  
hoggel
Addict
Rennlist Member
 
hoggel's Avatar
 
Join Date: Jan 2005
Location: SLC, Utah
Posts: 995
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by hoggel View Post
The 12v contact of the light should not go to 0V when the the bulb is in place, It should stay about 12V and the light should come on. You either have a bad ground that is not allowing enough current to illuminate the light or you have some high resistance between the fuse and the light that is limiting the current to the bulb.

[WRONG] Use a jumper from a 12V source (battery is right there) to one end of the bulb. Touch the other end of the bulb to the ground side bulb holder contact. Light? If yes, the problem is between the fuse and the 12V contact of the bulb holder. No light (and you know the bulb is good)? The problem is on the ground side. Pull the connector off the latch and jump the ground side pin to the opposite end of the light from the 12V. Light? If yes, the switch is not making good contact. No light? The problem is between the connector and ground.[/WRONG]
I'm sorry that I posted wrong information above.

[CORRECTION] The light in the luggage compartment is not controlled directly by the switch in the latch. The front latch switch is logic to the Alarm Control Unit. The alarm control unit turns on the "inside light" circuit by applying a ground to the luggage compartment light and the inside lights (in the 'automatic') position.

The ground for the switch on the luggage compartment lock is on the passenger wheel housing right.[/CORRECTION]

Last edited by hoggel; 06-12-2013 at 04:56 PM.
hoggel is offline  
Old 06-02-2013, 11:35 AM
  #5  
Aussie Alan 993
User
Thread Starter
 
Aussie Alan 993's Avatar
 
Join Date: Nov 2003
Location: Sydney Australia
Posts: 444
Likes: 0
Received 0 Likes on 0 Posts
Default

Thanks mate, that is very helpful, I will start there and hopefully get it sorted.
I'll post what I learn, hopefully get it sorted out.
Aussie Alan 993 is offline  
Old 06-02-2013, 03:30 PM
  #6  
BobbyT
Addict
Lifetime Rennlist
Member
 
BobbyT's Avatar
 
Join Date: Sep 2004
Location: CA
Posts: 1,865
Likes: 0
Received 0 Likes on 0 Posts
Default

Just a sidebar to this, but I found that if I leave the interior dome lights in the "automatic" position and lock the car with the remote (so the alarm is on), when I return two weeks later, the battery is stone dead. Apparently these settings creates a blind current draw...
BobbyT is offline  
Old 06-02-2013, 06:36 PM
  #7  
nine9six
Addict
Rennlist Member
 
nine9six's Avatar
 
Join Date: Oct 2011
Location: Socal
Posts: 5,346
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by BobbyT View Post
Just a sidebar to this, but I found that if I leave the interior dome lights in the "automatic" position and lock the car with the remote (so the alarm is on), when I return two weeks later, the battery is stone dead. Apparently these settings creates a blind current draw...
BobbyT,
Any chance your battery has seen better days? Curious as to how long its been in service?
Also, I wonder if you'd get the same results if you installed LED's in your cabin lights recepticles?
nine9six is offline  
Old 06-02-2013, 07:56 PM
  #8  
BobbyT
Addict
Lifetime Rennlist
Member
 
BobbyT's Avatar
 
Join Date: Sep 2004
Location: CA
Posts: 1,865
Likes: 0
Received 0 Likes on 0 Posts
Default

The battery is an East Penn 648MF, about a year old, so I'm confident it isn't a bad battery. The LEDs in the cabin lights might perform differently. For now, I just keep the dome lights in the off position, and turn them on as needed.
BobbyT is offline  
Old 06-03-2013, 06:09 AM
  #9  
Aussie Alan 993
User
Thread Starter
 
Aussie Alan 993's Avatar
 
Join Date: Nov 2003
Location: Sydney Australia
Posts: 444
Likes: 0
Received 0 Likes on 0 Posts
Default

Hi Fellas,
I didn't have a lot of time after work today but I now know the problem is NOT on the ground side.
I took the light out and tested it on a 12V house alarm battery - its good, so no problem with the globe or the holder.
I then took a wire from the negative post on the battery and connected it to the ground terminal on the holder and no light. I then did the same from the positive post and connected it to the positive terminal using its normal ground wire and we have light, so the problem is with the positive side and not the ground side of the circuit.
Next I'll need to start studying the wiring diagrams to find where the 12V is coming from.
I'll keep going, but not tonight.

Cheers
Alan

Last edited by Aussie Alan 993; 06-03-2013 at 11:07 AM. Reason: clarification
Aussie Alan 993 is offline  
Old 06-12-2013, 05:02 PM
  #10  
hoggel
Addict
Rennlist Member
 
hoggel's Avatar
 
Join Date: Jan 2005
Location: SLC, Utah
Posts: 995
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by Aussie Alan 993 View Post
Hi Fellas,
I didn't have a lot of time after work today but I now know the problem is NOT on the ground side.
I took the light out and tested it on a 12V house alarm battery - its good, so no problem with the globe or the holder.
I then took a wire from the negative post on the battery and connected it to the ground terminal on the holder and no light. I then did the same from the positive post and connected it to the positive terminal using its normal ground wire and we have light, so the problem is with the positive side and not the ground side of the circuit.
Next I'll need to start studying the wiring diagrams to find where the 12V is coming from.
I'll keep going, but not tonight.

Cheers
Alan
I just made this sketch for another thread. Fuse 11 also powers the glove box light, engine compartment light, buzzer, ... .
Attached Images  
hoggel is offline  
Old 11-23-2015, 10:16 AM
  #11  
wes911 Mill
New User
 
Join Date: Nov 2015
Location: South Lyon, MI
Posts: 3
Likes: 0
Received 0 Likes on 0 Posts
Talking 2000 Porsche 911 trunk light not working-easy fix

After reading the helpful posts and testing voltage and ground with my meter I did confirm it was the micro-switch. The micro-switch wires are not visible when looking down at the latch so they must enter into the luggage compartment behind the felt panels. So facing the latch and front of the vehicle i stuck my right hand index finger into the latch and touched & forced the micro-switch located on the right-side of the latch assembly and the light illuminated. So before you tear it all apart and replace the switch try this. And don't slam or drop the hood to shut it. Carefully lower the hood on to the latch where you will hear a click, then with the plams of both hands on both sides of the emblem gently push down until you hear the hood completely latch. Then use a polishing cloth to wipe your palm prints off the hood. And be glad you own a fine piece of Temperamental German engineering.
wes911 Mill is offline  
Old 11-23-2015, 10:38 AM
  #12  
Railmaster.
User
 
Railmaster.'s Avatar
 
Join Date: Feb 2015
Posts: 998
Likes: 0
Received 1 Like on 1 Post
Default

Originally Posted by wes911 Mill View Post
After reading the helpful posts and testing voltage and ground with my meter I did confirm it was the micro-switch. The micro-switch wires are not visible when looking down at the latch so they must enter into the luggage compartment behind the felt panels. So facing the latch and front of the vehicle i stuck my right hand index finger into the latch and touched & forced the micro-switch located on the right-side of the latch assembly and the light illuminated. So before you tear it all apart and replace the switch try this. And don't slam or drop the hood to shut it. Carefully lower the hood on to the latch where you will hear a click, then with the plams of both hands on both sides of the emblem gently push down until you hear the hood completely latch. Then use a polishing cloth to wipe your palm prints off the hood. And be glad you own a fine piece of Temperamental German engineering.
Watch the old 993 Porsche promo films on Youtube, there they advice You to press gently on the emblem when You close the hood!
Railmaster. is offline  
Old 11-25-2015, 04:17 PM
  #13  
pp000830
Shade Tree Fixer
Rennlist Member
 
pp000830's Avatar
 
Join Date: Jul 2004
Location: Richmond, VA
Posts: 5,430
Likes: 0
Received 1 Like on 1 Post
Default

Originally Posted by BobbyT View Post
Just a sidebar to this, but I found that if I leave the interior dome lights in the "automatic" position and lock the car with the remote (so the alarm is on), when I return two weeks later, the battery is stone dead. Apparently these settings creates a blind current draw...
This is not normal. When you lock the doors do both dome lights extinguish immediately? If they slowly go dark or remain illuminated your electrical system is not going into the sleep like mode. If things are working properly several draw items are shut down.

Could your problem be a sticking relay or an aftermarket item such as a audio poweramp tapped into an inappropriate hot wire?
pp000830 is offline  
Old 01-02-2016, 03:12 AM
  #14  
oldman40
Addict
Rennlist Member
 
oldman40's Avatar
 
Join Date: Nov 2012
Location: Seattle, WA
Posts: 544
Likes: 0
Received 0 Likes on 0 Posts
Default riddle me this

ok i will pile on this revived thread...

i haven't purchased a volt-ohm meter yet but for the engineering gurus in the rl crowd perhaps you can put me in the right direction or have dealt with this problem:

interior lights do not come on at all with door opening. but when i switch the light to 'always on' it works (both sides work this way). the door switches both trigger the annoying door open alarm when, yes, the door is opened, suggesting that the microswitches and door switches are working.

glove box light doesn't work, but the cig lighter and coin tray lights both work normally.

engine hood light not working.

frunk light not working.

all bulbs appear perfectly intact. battery well charged, no issues. no other electrical gremlins. no battery drains or dead battery issues even after weeks of non-usage.

so yes i know i need to check contacts with voltimeter, but any a priori ideas about what might be going on?

thanks!
oldman40 is offline  
Old 01-05-2016, 04:36 AM
  #15  
oldman40
Addict
Rennlist Member
 
oldman40's Avatar
 
Join Date: Nov 2012
Location: Seattle, WA
Posts: 544
Likes: 0
Received 0 Likes on 0 Posts
Default

Update for any merciful e. engineers out there:

Glove box light fixed with loose connection. Multimeter shows very weak voltage at the hood light housing, 0.7 with resistance of 23ohms. Hood micro switch working, but not sure how to test current, it seems like a closed system, no exposed contacts.

Any thoughts on where the resistance is coming from?
oldman40 is offline  

Thread Tools
Search this Thread
Quick Reply: Bonnet - hood - trunk light is not working - Not So Simple


Contact Us - About Us - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: