R34 Combo Meter/Instrument Cluster Question

[RB25Detonator]

R34 Combo Meter/Instrument Cluster Question

I replaced my globes ages ago with LED wedge T5 globes for my Instrument Cluster on my R34 GTT (manual). Since then the fuel gauge doesn't work anymore (only shows yellow light when fuel is close to empty). Recently I replaced the globes again with white LED wedge T5 globes and noticed that there are no screws where it says "GND" on the back of the cluster (right side). Is that normal? 

I would like to get my fuel gauge working again. I did have this problem ages ago and then I fixed it by cleaning the fuel sender last year, but I can't be F'd doing it again... It can't be dirty. It happened when I replaced the globes in the cluster. So many people get this problem and there is no answer out there to why it happens. So I would like to know if there is someone out there that have a solution to this problem before I go to try clean it. 

BTW, all wire harnesses to the cluster are pressed in very good and wire harness going to fuel tank is in firmly (I did check).

[RB25Detonator]

Also, this is from the R34 service manual. I did check the fuel gauge with a multi meter and it does work.

[steventt]

The fuel sender possibly. Take it out and check the resistance. If you dont know how to do that, get a normal test light, clip one end to ground, test a fuse to make sure the test light works, then touch the fuel sender wire or backprobe at the back of the instrument panel. Wait a while to see the guage go up, aporox 30 second to a minute max it will move up really slow. This verifies the gauge works. If yes, unplug the snder and do the same there, if no, possible/likely wire short under the carpet to the panel. If yes , the sender is sick, the arm is worn etc. Good luck repairing that, if it gave trouble before then it may be out. You can manually manipulate it to s33 if the reading changes, then see what is causing the problem. Investigate and let us know.

[Duncan]

As above, 99% the problem is with the sender not the dash

[RB25Detonator]

On 8/12/2017 at 1:06 PM, steventt said:

The fuel sender possibly. Take it out and check the resistance. If you dont know how to do that, get a normal test light, clip one end to ground, test a fuse to make sure the test light works, then touch the fuel sender wire or backprobe at the back of the instrument panel. Wait a while to see the guage go up, aporox 30 second to a minute max it will move up really slow. This verifies the gauge works. If yes, unplug the snder and do the same there, if no, possible/likely wire short under the carpet to the panel. If yes , the sender is sick, the arm is worn etc. Good luck repairing that, if it gave trouble before then it may be out. You can manually manipulate it to s33 if the reading changes, then see what is causing the problem. Investigate and let us know.

Hi Steventt, thanks for the reply.

I don't own a test light, the only thing I have is a little multi meter. I will try your test light methods when I get one. I took off the fuel sender plug and checked the resistance on the fuel sender. It definitely works, I get about 46 ohms. So it's not the sender its self. I think it might be the wire harness going from the sender plug to the cluster or the gauge. 

 

I saw this on the service manual:

So I tried this and all the gauges go up except for the fuel gauge. It just stays there.

So then I took off the glass bit from the cluster and manually moved the fuel needle up and it quickly goes down, so it definitely has power. I then took out the fuel gauge out of the cluster to do some tests on it:

So this gauge works right?

So now I'm thinking the harness might be the problem.

I did some more research. Apparently if you take off your harness from the sending unit (this black one):

 and ground/earth it then switch ignition on, the gauge should shoot up to the full mark. Mine doesn't. It just sits on empty.

So what's next? I'm gonna see if I can get my hands on a test light and try poke it from the back of the instrument cluster where the sender feeds into (looks like a purple wire) just like what steventt suggested above. Clamp it on ground and probe test light into where sender wire feeds into the back of the cluster right? Do you do it with the main harnesses connected to the cluster or take cluster out of car? Will the gauge go up without the harnesses connected to the back?

Edited August 19, 2017 by RB25Detonator
spelling

[steventt]

Ok this is some good progress.
You use the test light with the harness connected to the cluster.
In the interim while u waiting for a test light do a continuity test on the sender wire. From sender end to cluster end, then fom one end to ground.
Did you try taking out the sender unit and manipulating it and see if the reading changes? Try touching the silver variable resister contacts together by hand.
Also the pins in the connector mush be secure. The workshop manual will say what resistance u should get with the multimeter for both the gauge and sender.
Its simple - worse case scenario you would have to make a bypass wire.

[steventt]

The gaugr will not go up withoutthe harness connected to the back(unless you take the time to figure out what wire is 12v and which ones are ground, then connect the individual pins with female terminals to a 12v and ground source, then you can test it externally with thesemder etc)

[RB25Detonator]

17 hours ago, steventt said:

Ok this is some good progress.
You use the test light with the harness connected to the cluster.
In the interim while u waiting for a test light do a continuity test on the sender wire. From sender end to cluster end, then fom one end to ground.
Did you try taking out the sender unit and manipulating it and see if the reading changes? Try touching the silver variable resister contacts together by hand.
Also the pins in the connector mush be secure. The workshop manual will say what resistance u should get with the multimeter for both the gauge and sender.
Its simple - worse case scenario you would have to make a bypass wire.

Ok so, I've taken out the fuel sender and moved it up and down, ignition switched turned to on and the fuel gauge doesn't move. I then checked the resistance by probing the fuel sender wire and it does work. I get 6 omhs at full and 80 at empty. I then checked the continuity from the sender plug to the plug of the cluster and there is continuity. I then checked the continuity from the sender's ground to where it grounds and there is continuity.

So then I bought a test light (tested some fuses and it works). I then hooked the test light's ground to the negative of the battery and then with the key switched to on, i probed the back of the harness and get nothing!

It's this one right? number 7. I don't know what to try next. Are there any tests I can do on the cluster board?

 

[steventt]

Ok no high science here. You made all the proper checks, try keeping the test light probe for 1 minute if you have not already done so.
Next,remove the sender and check the contacts(3 wires from the back of the connector for the sender unit going down into the petrol etc should be the white one) make sure they are secure and if you are good at playing maze games you can test continuity from the plug to these wires.
Make sure all connections are secure - it may seem connected but a loose connection andnno connection is the same even though we getmultimetwr reading the functions arent properly secured like half way closing a bottle.
Dont be worried, we are thinking twice, even 3 times, before we replace anything. What u are doing is pin pointing all the systems that should function correctly, eventually we are going to pinpoint one and prove, evaluate the issue.
Right now worse case im leaning toward the cluster, if i had access to a spare or a buddy/friend/club member who has one and try their cluster, or better yet let them try urs. But lets not jump that far just yet.

[satiguer]

Hi Guys, just wondering if you managed to get the fuel gauge working again? Mine is not working after replacing the LEDs on the cluster. Any tips or advice will be greatly appreciated. Many thanks.

[GTSBoy]

On 8/29/2022 at 6:47 PM, satiguer said:

Hi Guys, just wondering if you managed to get the fuel gauge working again? Mine is not working after replacing the LEDs on the cluster. Any tips or advice will be greatly appreciated. Many thanks.

So....

Swap the original globes back in. Did it fix it? If no, then;

Work out what wire you broke while manhandling the cluster. Break out the multimeter and wiring diagram and go looking.