Two Questions: Speedo and Tail Lights
02-14-2010, 01:26 PM
#1
Rennlist Member
Thread Starter
Two Questions: Speedo and Tail Lights
I have a recently acquired 1980 928. I'm trying to get her back to her original beautiful condition. I have encountered a few problems:
1.) No tail lights. I cannot find a fuse. All other lights work except the tails. Am I missing something simple?
2.) My speedometer does not move. Is it electric or cable drive? I have not taken the cluster out yet. I have the 85mph cluster (needs changed!), but the illumination does not work and neither does the speedo. I do not have power at the relay board for the illumination. My tach works fine and so does oil, and I'm not sure on everything else.
1.) No tail lights. I cannot find a fuse. All other lights work except the tails. Am I missing something simple?
2.) My speedometer does not move. Is it electric or cable drive? I have not taken the cluster out yet. I have the 85mph cluster (needs changed!), but the illumination does not work and neither does the speedo. I do not have power at the relay board for the illumination. My tach works fine and so does oil, and I'm not sure on everything else.
02-14-2010, 02:11 PM
#2
Team Owner
get a fuse relay chart here 928gt.com on page 2 under tips and links print one off .
My guess is that the fuses may be dirty clean them with a pencil eraser, make sure to have the correct fuses in the correct positions.
For the tail lights there is a ground connection behind the right rear quarter panel liner.
To get to it,
first remove the right rear cargo hold down ,
then the 3 screws along the bottom of the RR liner, carefully pry the liner back just enough to get a 10mm wrench on the ground point, clean this with an eraser.
For the dash lights make sure you have power going to the rheostat under the pod and the 2 wires are connected to it ( usually the rheostats get corroded and fail) the dash dimmer is on the left side of the pod read the owners manual for a description.
For the speedo there are 3 pins that the wire guide plugs into on the back of the cluster these usually get corroded and that make the speedo not work, also there should be a connection in the spare tire well, check these connections before you remove the pod
My guess is that the fuses may be dirty clean them with a pencil eraser, make sure to have the correct fuses in the correct positions.
For the tail lights there is a ground connection behind the right rear quarter panel liner.
To get to it,
first remove the right rear cargo hold down ,
then the 3 screws along the bottom of the RR liner, carefully pry the liner back just enough to get a 10mm wrench on the ground point, clean this with an eraser.
For the dash lights make sure you have power going to the rheostat under the pod and the 2 wires are connected to it ( usually the rheostats get corroded and fail) the dash dimmer is on the left side of the pod read the owners manual for a description.
For the speedo there are 3 pins that the wire guide plugs into on the back of the cluster these usually get corroded and that make the speedo not work, also there should be a connection in the spare tire well, check these connections before you remove the pod
02-14-2010, 03:11 PM
#4
Team Owner
use the fuse relay chart to make sure the correct fuses are in position and the correct relays as well. Clean the ground wires over the CE panel as well as the red wire connections .
Also inspect the hot post for corrosion as well as the 14 pin connector above it
Also inspect the hot post for corrosion as well as the 14 pin connector above it
02-14-2010, 03:21 PM
#5
Rennlist Member
Rennlist Site Sponsor
The rear lights don't have individual fuses, as they are all powered thru the "Lamp Control Unit", sometimes called the Bulb Check Unit. This is a black box that monitors each rear light, and gives you a warning light if a tail light or brake light fails.
Check Fuse #10.
If the fuse is OK, check the side marker lights - if they work, the fuse and Lamp Control Unit are both OK.
Check for both power AND ground at the tail light bulb sockets. If you have both power and ground, the bulbs are obvious suspects. If you are missing the ground, Stan told you how to check that. Check the harness connectors as well.
If you have no power to either the side marker lights or the tail lights, the most likely problem is at the Lamp Control Unit.
Report what you find...
Check Fuse #10.
If the fuse is OK, check the side marker lights - if they work, the fuse and Lamp Control Unit are both OK.
Check for both power AND ground at the tail light bulb sockets. If you have both power and ground, the bulbs are obvious suspects. If you are missing the ground, Stan told you how to check that. Check the harness connectors as well.
If you have no power to either the side marker lights or the tail lights, the most likely problem is at the Lamp Control Unit.
Report what you find...
02-14-2010, 04:31 PM
#7
Team Owner
IIRC the BCM is on the end of the lower parcel tray on the right hand side of the car, under the glovebox