Fuel gauge, front fender marking lights quit working after new cluster installed

[data89]

Everything is working after changing from 3 light bezel to 7 light bezel and brand new circuit cluster. BUT, not the fuel gauge nor front side marker lights.
I taped off the contacts for temp gauge and ammeter gauge on the new circuit board because I installed Autometer gauges separately since I no longer have them and the Autometer gauges fit right in the bezel. These gauges are now wired to the fusebox directly.
I rewired the cluster plug correctly according to the numerous available instructions.
NOTE: Before the change, everything was working including the fuel gauge and front side markers.
Is there a problem because the circuit board connections are open and no longer used? For instance, should the temp gauge tabs be shorted to complete a circuit to the fuel gauge? And the ammeter gauge? (Autometer ammeter gauge is wired separately also).

[pjmoreland]

Take a look at the gauge cluster schematic dmjlambert made on this thread:
http://67-72chevytrucks.com/vboard/s...d.php?t=709847

Power for the fuel gauge is provided on pin 3 of the 12-pin connector that plugs into the back of the gauge cluster. Check for 12V on pin 3 as well as the post on the back of the fuel gauge that is connected to pin 3 via the circuit board. Also check for continuity between pin 4 and the other post of the fuel gauge as well as between pin 4 and the terminal on the fuse panel where the tan fuel sender wire plugs in.

There are variations in how the side marker lights are wired between the different years of the 67-72 trucks.
http://67-72chevytrucks.com/vboard/s...=707545&page=2

[data89]

I understand how you connect when using the circuit cluster factory temp gauge, but I am not...the temp gauge tabs are empty/open. I suspect I need to run a wire across the temp gauge tabs to complete the circuit so the fuel gauge has power. But, if I'm wrong, I don't want to burn something up.

[ray_mcavoy]

No, you don't need to (or want to) add any wires connecting the unused printed circuit tabs for the temp gauge or ammeter. Doing so would create a short circuit and likely burn up traces on the printed circuit.

Like pjmoreland said, the fuel gauge gets it's power directly from pin 3. The printed circuit does have a branch of that trace that also powers the temp gauge. But the circuit does not run through the temp gauge. So not having a factory temp gauge hooked up won't prevent the fuel gauge from working.

Also, double check the terminals that you re-pinned on the cluster plug. It's possible that a terminal didn't get latched securely into the connector, allowing it to pop back out when you plugged the connector back into the cluster.

[data89]

Thanks for clarifying that. Now I will pull the instrument panel out again and do as you suggested. Give me a day or so, it's cold in the garage.

Wait, but the other question...Why are my front side marker lights out? Are they not connected to the rear side marker lights (which are working, and so are all other lights)?

[data89]

Why are my front side marker lights not working and yet all others are working (including rear side marker lights)?

[ray_mcavoy]

The rear side markers are connected to the same circuit as the tail lights. The front side marker wiring varied a little by year. I think 68-70 or so had them wired to the same circuit as the front parking lights. Then 71-up had them wired between the front parking lights & front turn signals (which allowed them to flash with the turn signals).

Are your front parking lights & turn signals still working normally? And have you made any recent changes there ... such as LED bulbs?

[data89]

Originally Posted by ray_mcavoy

The rear side markers are connected to the same circuit as the tail lights. The front side marker wiring varied a little by year. I think 68-70 or so had them wired to the same circuit as the front parking lights. Then 71-up had them wired between the front parking lights & front turn signals (which allowed them to flash with the turn signals).

Are your front parking lights & turn signals still working normally? And have you made any recent changes there ... such as LED bulbs?

All lights are working but for the front/side marker lights. Factory bulbs, tested throughout. It's curious that they stopped working along with the fuel gauge, as though they are on the same circuit.

I'll try a physical search of the wiring to see where they get power from.

[VetteVet]

Here is the diagram of the front turn signals and side markers. The power for the marker lights begins at the fuse panel with the 12-gauge orange wire which feeds the light switch. From there it connects with a brown wire to all the small lights.
A 12-gauge wire from the key switch accessory terminal goes to the fuse panel and feeds the turn signal flasher, via a purple wire. Then the purple wire goes to the steering column harness and feeds the turn signal switch.
The parking and marker lights are not on that circuit. They come off the accessory side of the fuse panel as I said.


turn signal marker.pdf



The orange wire at the head light switch also feeds the dash light control rheostat in the headlight switch which runs back to the fuse panel via a green wire to the dash lights fuse. From there a gray wire goes to the circuit panel plug-in.
I suspect that your dash lights not working, begins at that point. Or possibly at the orange wire connection on the headlight switch.
I have those diagrams if you need me to post them.

[data89]

Okay, update regarding front side marker lights. This threw me off...both were working before the circuit cluster swap. Anyhow, I decided to check them for power and found that the left side bulb had blown and the right side bulb wasn't making contact. Cleaned and replaced and now have both working.

Now everything works but the fuel gauge, so will take the cluster back out and check power feed.

[data89]

Originally Posted by VetteVet

Here is the diagram of the front turn signals and side markers. The power for the marker lights begins at the fuse panel with the 12-gauge orange wire which feeds the light switch. From there it connects with a brown wire to all the small lights.
A 12-gauge wire from the key switch accessory terminal goes to the fuse panel and feeds the turn signal flasher, via a purple wire. Then the purple wire goes to the steering column harness and feeds the turn signal switch.
The parking and marker lights are not on that circuit. They come off the accessory side of the fuse panel as I said.


Attachment 2252114





The orange wire at the head light switch also feeds the dash light control rheostat in the headlight switch which runs back to the fuse panel via a green wire to the dash lights fuse. From there a gray wire goes to the circuit panel plug-in.
I suspect that your dash lights not working, begins at that point. Or possibly at the orange wire connection on the headlight switch.
I have those diagrams if you need me to post them.

That's a handy schematic, thank you.

[data89]

Regarding the 2 fuel gauge tabs on the fuse panel. The top tab has no power. The bottom tab has power. Shouldn't the top tab also have power with the ignition switch on?

The wires going into the ignition switch all have power.
All fuses checked and have power on every one.

Is the no power on the top tab problem in the fuse panel connection inside?

I'm trying to figure out why my fuel gauge doesn't work (it did before switching the printed circuit cluster).

In the diagrams, I see that the fuel gauge wire is connected to the top tab.

[pjmoreland]

The tan fuel tank sender wire plugs into the top tab that has a notch in the opening. With the tan wire unplugged and ignition on, you should read in the ballpark of 8.5V on that tab. If you aren't getting any voltage there, then here are a few possible reasons:

1) Check your Cluster Feed fuse. It powers the fuel gauge.

2) No power connection to the fuel gauge. With ignition on, check for 12V on the fuel gauge screw terminal that is on the driver side of the gauge (comes from pin 3 of the gauge cluster .

3) No connectivity between the fuse panel top tab and the fuel gauge. Check for continuity between the top tab and the fuel gauge screw terminal that is on the passenger side of the gauge (passes through pin 4 of the gauge cluster connector).

[ray_mcavoy]

Of those 2 tabs on the fuse panel, only the top one is for the fuel gauge. The one below it is a power receptacle connected to the glove box / spot lamp fuse.

And that top tab is wired to the sending unit side of the gauge ... it's not a power feed to the gauge. Although, I believe it is normal to see some voltage there with the key on due to it feeding through the coils in the gauge.

Edit: looks like pjmoreland beat me to it ... and gave you the voltage to look for at that terminal.

[data89]

Excellent information, thank you both, now I have something to go on. I will follow through on this tomorrow.

[dmjlambert]

If by saying tabs on the fuse panel you mean the terminals that you can plug wires into, there is only one terminal related to the fuel gauge and it is marked FUEL GA. on most fuse panels. It really doesn't have anything to do with the fuses, and doesn't really belong on the fuse panel, but I suppose it was put there as a convenient place to plug in a wire. The wire that plugs in there is the tan wire from the fuel tank. That wire provides ground through a rheostat in the gas tank. With the gas tank wire unplugged from that terminal and the ignition switch key in the on position, there is near 12 volts on that terminal. With the gas tank wire plugged into that terminal and the ignition switch key in the on position, and sticking the multimeter probe into the back of the plastic connector where the tan wire goes into the connector so I make contact to the metal in there, there is less voltage on it. With my 1/4 tank of fuel I get about 3 volts. That voltage is coming from the fuel gauge. The voltage travels from the driver side post of the fuel gauge, through the gauge windings and then to the passenger side post of the fuel gauge, and through the printed circuit to the tan wire and finally into the back of the fuse panel attaching to that terminal. If the driver side post of the fuel gauge is not supplied 12 v with the ignition switch key in the on position, that will prevent the gauge from working (and also prevent the voltage from showing up on that terminal of the fuse panel). Keep on tracking down that problem.

[dmjlambert]

I'm a pretty slow typist apparently.

[VetteVet]

Here's a post by IlludiumQ36 that has a very good diagram of the fuel gauge circuit.

http://www.67-72chevytrucks.com/vboa...d.php?t=841373

The thread is only a few down from this one.

[data89]

Vettevet, I checked the diagrams, every bit helps.

Meanwhile, I checked voltage and resistance. It appears that the tan wire from the tank goes behind and inside the fusebox to the top tab. Resistance on the wire disconnected is approximately 1.2K ohms (I'm assuming that's the resistance of the wire).
With that wire at the tab and from the tank disconnected I have 12V ign on.
From the tab to ground, ign on or off, I have 0V.

Conclusion now is that I have to pull the instrument panel off (under the dash the only 2 wires that are tan are the radio and the dome light) and follow the wires from the cluster plug.

[data89]

Okay, warmed up, back at it.

Everything works except the fuel gauge. Gauge tested good, tank sending unit tested good. Wire colors checked on cluster plug correct. Sending wire from tank plugged into top fuel tab on fuse panel.

New 7 hole cluster circuit with Temp-Fuel-Alt-Bat two tabs taped off as they are not used. These gauges are wired separately (Autometer)

12v at ign tab on fuse panel with ign turned on. Shouldn't I then have 12V at pin 3 on the cluster plug? Or do I need to run a separate wire from the fuel gauge 12V pin directly to the fuse ign tab?

[dmjlambert]

Yes, pin 3 is the pink wire, it has power when key is on. Check the 3A fuse labeled CLST FEED next to IGN UNFUSED terminals, purple outlined. That is what powers the pink wire. It will also affect the BRAKE light on the instrument cluster, which should turn on for bulb test when you are cranking the engine.

[data89]

You've been a great help, thanks. I do believe my gas gauge is working now. I have become very familiar with all my wires and fuse box connections, and am in a close relationship with the back of my cluster. Your last picture really helped clarify the fusebox.

2 things were wrong...unbeknownst to me, the 3 amp fuse had blown sometime during the process of troubleshooting, and the sending unit wire had not been plugged into the correct tab on the fusebox.

I have replaced all the dash bulbs with LED lamps and bench tested everything, since there's a neg/pos issue with them too. Now I can see my gauges in the dark.

Now on to the side window channels and new windshield.