i've read and read.... tail light & brake light not working. unless i open a door??? - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > Models > Jeep Grand Cherokee & Commander Forums > ZJ Grand Cherokee Forum > i've read and read.... tail light & brake light not working. unless i open a door???

Year End Clearance Sale! Save 20%Santa Kolak Announces: Kolak Exhaust 20% Off Sale!ROCK BOTTOM prices on LIFT KITS at Rockridge4wd!! WANT TO

Reply
Unread 12-22-2014, 10:27 AM   #1
zjj
Registered User
1994 ZJ 
 
Join Date: Jan 2012
Location: sumner, ia
Posts: 60
i've read and read.... tail light & brake light not working. unless i open a door???

So I bought a 94 zj with the brake lights and running lights not working correctly. I've owned 3 others prior and fixed this similar issue before by cleaning up the bulb terminals. This one is challenging me in many ways...
Last night i lifted the gate and pulled both tail light housings and inspected the bulbs and sockets. Everything looked very clean and normal and even noticed some dielectric grease in the sockets. Put them back in and turned the lights on and everything worked!!! awesome...until i closed the hatch. Then they went out.... Did some testing and noticed that with the hatch open, the tail lights and brake lights would work, but as soon as i closed the drivers door (or just pushed the door pin switch "in") the lights would go out again. I checked all the wiring locations that were obvious in the hatch area and even unplugged the wires from the entire tail gate, to no avail. by the end of the night, the only way the tail lights would light up was if i opened the passenger rear door, which happens to be the only door that will not turn on the dome lights inside when it opens. Where would you start?? Please help. I need to get my daughter back on the road asap. It is a v8 laredo '94. All windows, dome lights, dash lights, door locks etc work. All fuses are good, on the passenger side of the dash and the engine compartment by the battery.

__________________
"If we ever forget that we're one nation under God, then we will be a nation gone under." Ronald Reagan
zjj is offline   Reply With Quote Quick reply to this message
Unread 12-22-2014, 10:29 AM   #2
zjj
Registered User
1994 ZJ 
 
Join Date: Jan 2012
Location: sumner, ia
Posts: 60
I did notice that the front drivers blinker/parking marker light is out and makes the blinkers flash quickly. I will replace that tonight. Looks like i have to remove the whole headlight assembly...Could my whole problem be in that and a bad door post switch?? Where are the main areas to check the chassis grounds and how do i trouble shoot the grounds. It seems funky enough that it acts like a bad ground.
__________________
"If we ever forget that we're one nation under God, then we will be a nation gone under." Ronald Reagan
zjj is offline   Reply With Quote Quick reply to this message
Unread 12-22-2014, 12:56 PM   #3
Nenenaiad
Registered User
1997 ZJ 
 
Join Date: May 2011
Location: Stourbridge, Uk
Posts: 29
Hi Zjj,

Sounds like an earth problem to me, for a number of reasons.

Firstly stop and tail lights are housed in a single 21/5W bulb. This has three connections. There is a feed to the 5 watt part for the tail light, one to the 21W part for the stop lamp. The case of the bulb goes to ground as do the other end of the elements in each bulb. To affect both parts of the bulb implies the common earth connection.

This is what I suggest you do.

Put your side lights on which should mean that if your tail hatch is open the lights should be lit at the back.

Gain access to the Right / Tail Stop Lamp so that you can see/ touch the wiring at the back of the bulb. Remove right tail lamp assembly to do this....three bolts I think. You will see the following cables, a PK/WT (pink with white tracer)stop bulb feed, an LB(light blue)for tail light feed and a BK(Black)for the earth. You should see these behind the lit tail light. You are in the right place.

Now close the tailgate, from what you said the tail lights go off. Good....

Now open it again....Tail lights back on .......Good...

The fault is consistent.

Now speak to your wife and get some dress making pins. Get a small piece of timber as well.

Now with the timber behind it push a pin through the middle of the insulation of the Black cable until it goes right the way through. The purpose of all of this is to enable you to make connections to this cable without cutting it. You will have pierced through the wire in the cable as well.

Now locate a piece of spare cable say three feet long and strip both ends an inch or so. Now wrap one end of the cable around the pin and locate part of the rear body of the car which represents a good earth. Possibly somewhere in the region of the tailgate catch should do it. Connect the other end of the wire here.

So you have created a new earth for the Right rear Tail/Stop Bulb. Try opening and closing the tailgate. Does it still go out when closed or does it stay on? If it stays on you are looking for an earth problem, which is via the Black Cable.

Let me know what you find and I will help you some more. I have a ZG workshop manual here so I can investigate the earth for you if we need to.

I am in the UK, so you may get a bit of a time lag, but I will respond as soon as possible. I look after my daughters car as well so I understand.

Regards


Dave







Put the parking lights on.
Nenenaiad is offline   Reply With Quote Quick reply to this message
Unread 12-22-2014, 01:26 PM   #4
Nenenaiad
Registered User
1997 ZJ 
 
Join Date: May 2011
Location: Stourbridge, Uk
Posts: 29
Re your second point. Indicator bulb failures are meant to show themselves as a warning to the driver by increasing the flash rate.

Change the bulb and you should be OK

Re the other fault......we eliminate and pick up information as we go....As I said let me know what you have found and come back to me. Are you ok measuring voltages etc....let me know that as well.

Regards


Dave
Nenenaiad is offline   Reply With Quote Quick reply to this message
Unread 12-22-2014, 02:32 PM   #5
Marcos
Registered User
1993 ZJ 
 
Join Date: Mar 2005
Location: Germantown, MD
Posts: 745
The ground for all of those circuits are spliced together in the wiring bundle that passes along the sill of the passenger side front door, and the actual ground terminal is described as being in the right kick panel. Unfortunately I couldn't find a diagram of the exact location of the ground terminal, but it should be pretty evident. it may be one of the instrument panel bolts.

What is likely happening is that the exterior light circuits have lost their connection to ground, and are being grounded through the splice when one of the door jamb switches is activated. Start by looking for that ground connection in the kick panel.
Marcos is offline   Reply With Quote Quick reply to this message
Unread 12-22-2014, 02:47 PM   #6
zjj
Registered User
1994 ZJ 
 
Join Date: Jan 2012
Location: sumner, ia
Posts: 60
ALL very good starting points!! I love internet forums. You get good information from good people who are passionate about the topic at hand. Blessings to the both of you and I will reply tonight after doing some of these tests. Yes, i have a good meter and can test voltage etc... I will be chasing down what appears to be a possible PCM or IAC issue. I'll start a new thread for that here shortly.
__________________
"If we ever forget that we're one nation under God, then we will be a nation gone under." Ronald Reagan
zjj is offline   Reply With Quote Quick reply to this message
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.
Note: All free e-mails have been banned due to mis-use. (Yahoo, Gmail, Hotmail, etc.)
Don't have a non-free e-mail address? Click here for a solution: Manual Account Creation
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.


Thread Tools






Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.