84 300D Inst Cluster question
 

I am running down a ground issue on my sons 1984 300D

Two questions
#1 Pin 15 from circular connector is ground-but has trace peeled up-anyione know where it goes?


#2
At the back of the instrument cluster above the dimmer rotary control and below the oil pressure input is a Black relay box
What is it ?

I have not seen this "relay" on any other instrument clusters-anyone know what it does?

This is from the FSM...the last bit shows the pin configuration.

I'm not sure what's above the rheostat...

edit: here's where the grounds go...

Matthew

Thanks
I guess I still need more info-I am looking for the circuit board schematic for the 123 1984 300D instrument cluster.

Anyone have any on line info on where I can locate circuit board schematic for the 123 1984 300D instrument cluster.?

if you suspect a ground issue, you might be able to what I did to sort out a weird ground situation...I added a ground wire from the one of the attachment screws of the speedo to the frame behind the cluster.

After I removed the cluster to paint the needles, I had this intermittent issue with the seat belt light and the left side gauge needles going nuts. The ground wire fix those issues c

There is a common (for me anyways on 2 different cars) trace that burns up and causes your temp and fuel gauges to go nuts. I just wired over the burn, and have been fine. Not sure what caused it in the first place, but all is well 30k miles later.

Mine does the exact same thing. Jumping the burned trace did nothing and it only occurs while moving.

1. Pin 15 goes all over the instrument cluster. Its the ground for the lights bulbs and clock.

2. If the black box you are asking about is behind the speedometer, thats the engine speed sensor. It has something to do with emission control on my car.

No, on the back of the speedo is the vehicle speed sensor for the cruise control.

Mine was caused by a short in the left rear door window motor. The wires were shorted on the hinge inside that black rubber accordion looking thing. It travelled all the way to the cluster passing thru the window switch.

correct