Instrument cluster

[OntarioMax]

I've taken the cluster apart for repair and the speedometer bolts are not fitting, specifically the brass ground.
Where does it go?

 

[OntarioMax]

I'm posting another image to show the screw with the ground.
Are The other long ones necessary?

 

[MasterBlaster]

Any help?
Here's a pic from my 2020 post where I fixed a break in a trace.

 

[OntarioMax]

Any help?
Here's a pic from my 2020 post where I fixed a break in a trace.

What does the dual connector under the Stupid resistor comment function to do?
I have a Yellow/White wire that connects to the one on the left. Is the right one the same or does it function for something else?

 

[MasterBlaster]

What does the dual connector under the Stupid resistor comment function to do?
I have a Yellow/White wire that connects to the one on the left. Is the right one the same or does it function for something else?

? Your other posts seems to show a Yellow, with a Purple/White.

It's all the same connector... terminal "E".
A bent piece of copper riveted and soldered to the board, just like the other round terminals that attach the speedo to the case and provide electricla paths.

On the other side, it's called "AC", I assume because the Purple/White tells the A/C how fast you're going, so it can compensate? The yellow talks to the Cruise and Fuel ECU, likely for the same reasons. I'm not 100% positive, because I wasn't there when it was being designed.

Anyway, here's the front and back of my 1990 740 speedo for comparison:

 

[OntarioMax]

? Your other posts seems to show a Yellow, with a Purple/White.

It's all the same connector... terminal "E".
A bent piece of copper riveted and soldered to the board, just like the other round terminals that attach the speedo to the case and provide electricla paths.

On the other side, it's called "AC", I assume because the Purple/White tells the A/C how fast you're going, so it can compensate? The yellow talks to the Cruise and Fuel ECU, likely for the same reasons. I'm not 100% positive, because I wasn't there when it was being designed.

Anyway, here's the front and back of my 1990 740 speedo for comparison:

View attachment 31798

Mine does not look the same. if that's the view underneath the plastic then I stand corrected.

 

[MasterBlaster]

if that's the view underneath the plastic

That it is. Circuit board is currently not attached to the rest of the speedo.

 

[OntarioMax]

I see.
You're showing how it comes through the back of the board.

 

[OntarioMax]

Are you familiar with the back of the fuel gauge and which screws are positive and negative?

 

[1990Volvo740GLNonTurbo]

It might be too much trouble to go in there and fix the capacitors and resistors. Getting a working replacement is easier if it can be found.

 

[MasterBlaster]

Are you familiar with the back of the fuel gauge and which screws are positive and negative?

Maybe, maybe not.

 

[OntarioMax]

What about the Coolant temperature gauge. Where are those connections on this?

 

[MasterBlaster]

What about the Coolant temperature gauge. Where are those connections on this?

Both on plug B. Same power and ground from D4 and D3.

 

[OntarioMax]

So I should get reading with a multimeter at the two screws, one circled in green and the other in yellow?

 

[1990Volvo740GLNonTurbo]

I have a question about the screws.
Do they only go into the holes on the outside edge of the panel?
Are there more than two sizes of screws on the instrument panel?
I would also like to ask if anyone has mentioned the location of the Tachometer.
My speedometer is working, but my Tachometer is not. I presume that the signal is going to the device since the Speedometer and Tachometer use the same source.
Is my presumption correct?

 

[1990Volvo740GLNonTurbo]

So I should get reading with a multimeter at the two screws, one circled in green and the other in yellow?

Just go and try it using the voltage setting first and then the ohms setting. Write the readings down.

 

[MasterBlaster]

My speedometer is working, but my Tachometer is not. I presume that the signal is going to the device since the Speedometer and Tachometer use the same source.

Speedo uses the sensor in the rear differential case via D1 and D2.
Tachometer uses the ground signal from the power stage/coil via the single red/white wire.

Just go and try it using the voltage setting first and then the ohms setting. Write the readings down.

You won't get any useful numbers either way.
Unplug the multi-wire connector and Ohm the Y/Blk + Y/Wht if you want to check the sensor.
The gauge itself is a rather complicated little circuit board attached to a "balanced-coil" movement
that controls the needle position. It's not an ancient heated bi-metal strip type gauge.

A few pics from 2014, the last time I had it apart just for fun:

 

[OntarioMax]

Speedo uses the sensor in the rear differential case via D1 and D2.
Tachometer uses the ground signal from the power stage/coil via the single red/white wire.



You won't get any useful numbers either way.
Unplug the multi-wire connector and Ohm the Y/Blk + Y/Wht if you want to check the sensor.
The gauge itself is a rather complicated little circuit board attached to a "balanced-coil" movement
that controls the needle position. It's not an ancient heated bi-metal strip type gauge.

A few pics from 2014, the last time I had it apart just for fun:

View attachment 31900

How about touching the leads of the wires together that attach to the sensor in the cylinder head?

 

[MasterBlaster]

How about touching the leads of the wires together that attach to the sensor in the cylinder head?

It should spike the gauge to full hot.
Just don't do that to the temp sensor for the ECUs.

 

[MasterBlaster]

Edited above reply.
I was thinking or the ECU temp sensor for a second.
Shorting the GAUGE sensor wires should be okay.
Just don't mix them up.