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New Engine Compartment Light not working and wiring is HOT

Hi everyone,

In the 11 years I've owned my '87 Carrera, the engine compartment light has never worked. I tried replacing the bulb, and it still didn't work. I've now replaced the entire light assembly (the old one was not looking good). When I turn on the parking lights, the wiring to the engine compartment light immediately gets HOT. I immediately turned the lights off and the wire cooled.

Before pulling the fuse (4th from the front of the car - controls driver side parking lights and engine compartment light), I noticed that both front parking lights worked, but the rear driver side light did not. When I pulled the fuse, the front drivers side stopped working and the engine compartment light wiring stayed cool. I noticed that the fuse was 25 Amp! Bentley calls for a 5 Amp. Yikes...

Any thoughts on what may be the issue?

Thanks!
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Andy - 1987 911 Carrera Coupe

Last edited by polizei; 10-11-2018 at 08:12 PM..
Old 10-11-2018, 07:04 PM
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Iíll be watching this thread. My engine light used to work after I cleaned up all the contacts. Now itís not working and hasnít for a while.
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1966 VW Beetle, 6V
2016 BMW 328i
Old 10-11-2018, 07:43 PM
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I suspect your wiring to the light housing is shorting to ground. Likely at the housing.
Fairly common.
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Dennis
Euro 1978 SC Targa, SSI's, Dansk 2/1, Bitz kit EFI.
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Old 10-11-2018, 08:23 PM
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Quote:
Originally Posted by timmy2 View Post
I suspect your wiring to the light housing is shorting to ground. Likely at the housing.
Fairly common.
Thanks. I checked the wiring, and it looks like the positive & ground cables are secured well to the housing. I don't see any tears in the wire sleeves. Any suggestions on what to troubleshoot next?
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Andy - 1987 911 Carrera Coupe
Old 10-12-2018, 06:16 AM
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I fixed my fuse issue, but my fix may not apply. There are several threads here like this one...

Fuse for driver's side running lights keeps popping
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Frank Amoroso
1987 911 M491 Coupe
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Old 10-12-2018, 08:18 AM
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Quote:
Originally Posted by polizei View Post
Thanks. I checked the wiring, and it looks like the positive & ground cables are secured well to the housing. I don't see any tears in the wire sleeves. Any suggestions on what to troubleshoot next?
Did you test with a meter? One contact on lamp is power, should be no path to ground from it.
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Dennis
Euro 1978 SC Targa, SSI's, Dansk 2/1, Bitz kit EFI.
Need a New Wiring Harness? PM or e-mail me. Search for "harnesses" in the classifieds.

Last edited by timmy2; 10-12-2018 at 08:24 AM..
Old 10-12-2018, 08:22 AM
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+1....power shorted to ground.
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Old 10-12-2018, 08:41 AM
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I had this same problem on my '85 and took me a while to figure it out. I replaced my rusty old light with a new one and wound up blowing the fuse when I turned the lights on. There was a short from the 12V wire to ground that I could measure with a meter. It went away after I pulled the light and let it hang in the air. After trying all sorts of tape and shielding, I finally tried rotating it 180 degrees and that cured the problem. Evidently these can only be installed one way due to the way the ground return is wired up. Hope that helps.
Bill

Last edited by wjdunham; 10-12-2018 at 09:42 AM..
Old 10-12-2018, 09:39 AM
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Hi Polizei- Agreeing with @wjdunham on position- here's a shot from the owners manual (note position) Also- I switched over (no pun intended) to an LED bulb as well- lower voltage, low heat.

Old 10-12-2018, 12:07 PM
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...and with the LED bulb:
Old 10-12-2018, 12:08 PM
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New Engine Compartment Light not working and wiring is HOT

I had the same issue. You probably have the positive and negative reversed at the light housing like I did


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Old 10-12-2018, 12:42 PM
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Quote:
Originally Posted by Missed Approach View Post
...and with the LED bulb:
WOW let the sun in baby! Nice upgrade.
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Old 10-12-2018, 12:52 PM
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Quote:
Originally Posted by Missed Approach View Post
...and with the LED bulb:
May we have the top secret p/n for the led bulb?

Best,

Gerry
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Per Road and Track magazine:
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Old 10-12-2018, 12:59 PM
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Light.

Quote:
Originally Posted by polizei View Post
Hi everyone,

In the 11 years I've owned my '87 Carrera, the engine compartment light has never worked. I tried replacing the bulb, and it still didn't work. I've now replaced the entire light assembly (the old one was not looking good). When I turn on the parking lights, the wiring to the engine compartment light immediately gets HOT. I immediately turned the lights off and the wire cooled.

Before pulling the fuse (4th from the front of the car - controls driver side parking lights and engine compartment light), I noticed that both front parking lights worked, but the rear driver side light did not. When I pulled the fuse, the front drivers side stopped working and the engine compartment light wiring stayed cool. I noticed that the fuse was 25 Amp! Bentley calls for a 5 Amp. Yikes...

Any thoughts on what may be the issue?

Thanks!
Remove the housing, and the bulb, then look for a short on the +12v.

And, verify that the spacer between the housing and the deck lid
is intact.

The spacer serves as an insulator between the +12v and the chassis ground.

Also, the parking lights must be on for the engine compartment light to work.

Not sure about the requirement for the 25A fuse. I think the Bentley is correct.

pm me as need.

Gerry
__________________
1986 911 Targa.
Per Road and Track magazine:
Only in L.A.:
In the window of a bar in Hermosa Beach, California.
"Happy Hour prices during all car chases."

Last edited by 86 911 Targa; 10-12-2018 at 02:28 PM..
Old 10-12-2018, 02:13 PM
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I disconnected the engine bay light and cleaned up all the contacts with a Dremel. This is a fine piece of German engineering. Really is more at home in my 66 VW than the Targa. Still no joy by the way.
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Old 10-12-2018, 07:01 PM
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Gerry- I am searching for the Part Number for the LED replacement, (its been a few years since I made the switch)

Last edited by Missed Approach; 10-12-2018 at 09:08 PM..
Old 10-12-2018, 07:02 PM
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Got the light to come on momentarily, but wonít turn on consistently. If anyone happens to have an exploded view of how the light housing is assembled to deck lid that would be great. I donít have a spacer or washer that fits between the fixture and engine lid. I tried to turn the light on without the black dome housing on. The light wouldnít turn on. It almost looks like the two housing retainer clips are contact points (I confirmed they have nothing to do with switch electrics! Although the black housing needs to snug down as tightly as possible) When I put the housing back on the light lit up briefly.
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Last edited by rokemester; 10-13-2018 at 09:09 AM..
Old 10-12-2018, 08:54 PM
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A good night sleep often helps clear my mind and allows the information I’ve gathered the day before to settle in. In a previous comment here “verify that the spacer between the housing and the deck lid
is intact. The spacer serves as an insulator between the +12v and the chassis ground.” it was said that the housing needs to be insulated from the car body (the deck lid). Often times critical parts/washers are missing when we go to repair our cars. This was the case here. I fabricated a thin hard plastic gasket from a take away food container top. This led to the proper routing of the gray power wire and the brown ground wire to the light.
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1966 VW Beetle, 6V
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Last edited by rokemester; 10-13-2018 at 09:16 AM..
Old 10-13-2018, 04:59 AM
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Here are a few pics to show insulator fab and wire orientation.







I learned that is important to have the wires enter between light housing and insulator and up through hole/slot in housing. This allows black dome cover to fit snug and allow complete movement for the cover switch. Mine is still finicky and I need to give it an extra push to get it to light. Just want to keep the original as Iím guessing the new ones arenít as solid.





Thanks for the great information from the forum members and the fellow 87 owner who started this thread. This one had been bugging me.
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Old 10-13-2018, 05:23 AM
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Quote:
Originally Posted by 86 911 Targa View Post
May we have the top secret p/n for the led bulb?

Best,

Gerry
I have a message into Carmagic to see if they have a LED tube bulb that will hold up to the engine compartment heat.
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Old 10-13-2018, 09:36 AM
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