instrument cluster warning lights

[Tom]

The LEDs are polarity sensitive while incandescent isn't. which means you might have to rotate the bulb 180 degrees to make it work. Bit frustrating if the warning isn't lit up

Agreed. I mentioned above for that reason that the lower pad on the central warning light socket is the positive side.

[blade7]

I did the reflector foil refurb, and the backlighting has improved. Changed to LED's too, but still no indicator warning light, or the big red warning light above it . I'm wondering if the fault is in the cluster, or the wiring to it.

Ok, I got out the test cluster and can help you test if the main warning light is working or not. That light goes on when edge connector B4 has 12 volts and A13 has is grounded. Importantly for LED conversions, in the light socket for the main warning light, the lower copper pad carries 12 volts and the upper pad carries the ground. There are a number of diodes in the circuit that make checking continuity with a multimeter a challenge, so it's easiest to power it up and see if the light goes on. If not, the LED is getting the wrong polarity, the LED doesn't work, or there's something wrong in the flexible printed circuit board. If it does light up, then your problem is most likely not in the cluster, but rather the signals going to it....



b4-power.jpg
This red clip has 12 volts from my adjustable power supply, but any 12 volt source is fine. I traced edge connector B4 directly to that copper post so just used that post since the clip holds better there.




a13-ground.jpg
Then put ground on edge connector A13 (behind the fuel gauge) -- careful not to short to the other fingers.




warning-light-on.jpg
With 12v and Ground applied as shown, the warning light 'should' pop right on.

Thank you Tom. Can you advise where the turn signal indicator bulb is powered from, if that isn't working the car will fail the annual inspection over here.

[Tom]

Thank you Tom. Can you advise where the turn signal indicator bulb is powered from, if that isn't working the car will fail the annual inspection over here.

Will do. In the meantime, I assume your actual blinkers do work on the outside of the car?

[blade7]

Thank you Tom. Can you advise where the turn signal indicator bulb is powered from, if that isn't working the car will fail the annual inspection over here.

Will do. In the meantime, I assume your actual blinkers do work on the outside of the car?

Yes, all the blinkers work on the outside of the car. From the hazard switch and the stalk by the steering wheel.

[Tom]

Thank you Tom. Can you advise where the turn signal indicator bulb is powered from, if that isn't working the car will fail the annual inspection over here.

Will do. In the meantime, I assume your actual blinkers do work on the outside of the car?

Yes, all the blinkers work on the outside of the car. From the hazard switch and the stalk by the steering wheel.

In the cluster, the turn signal / flasher light bulb is powered by pins B6 and B7. B7 is the lower pad on the bulb socket and appears to be positive only when activated by the relay (so LED positive side down). At first I thought the circuit flipped polarity as the lights flashed, but I don't think that's the case. The circuit is still funky though, with the B7 supplying 12v from the relay but the ground being supplied through the blinker bulbs when they are not on. LEDs may act oddly as a result. If in doubt, try a regular bulb.

blinker-pins.jpg (196.24 KiB) Viewed 166 times

After scratching my head over the schematics, I convinced myself that the cluster light could not be on when the blinkers are on, so it dawned on me they must alternate. Sure enough, the cluster light and outside lights flip flop -- the interior indicator can only light up when the outside lights are off. Here's a video of theory in action.

[blade7]

Thanks again, I'll try a known good standard bulb. Is it just a coincidence those 2 bulbs next to each other aren't working ,or do they have something in common?

[Tom]

Thanks again, I'll try a known good standard bulb. Is it just a coincidence those 2 bulbs next to each other aren't working ,or do they have something in common?

The traces are close together on the flexible circuit board, so if part of the board is damaged, maybe it took out both... Or the edge connector could be damaged. Does the high beam light work? That's the closest other bulb on that edge connector. The flasher bulb has a very separate and discrete circuit in the cluster -- b6 and b7 go straight to the bulb socket, so it's not like it is electronically inter-connected with the warning light bulb in the cluster. I suppose there could be some interaction downstream in the chassis wiring, but that doesn't seem likely to me.

[blade7]

The main beam warning light was very dim, but changing the bulb solved that. If there is an issue in the cluster, could I take a feed from the closest indicator wire, and use that to power a warning bulb?

[Tom]

The main beam warning light was very dim, but changing the bulb solved that. If there is an issue in the cluster, could I take a feed from the closest indicator wire, and use that to power a warning bulb?

Not really. The main warning light positive rail is boxed in with diodes, so if you were to jumper something over to it, you'd like short out that logic and create problems. If the new bulb solved the problem, why do you want to borrow a feed? What's the problem you are trying to solve?

[blade7]

The main beam warning light was very dim, but changing the bulb solved that. If there is an issue in the cluster, could I take a feed from the closest indicator wire, and use that to power a warning bulb?

Not really. The main warning light positive rail is boxed in with diodes, so if you were to jumper something over to it, you'd like short out that logic and create problems. If the new bulb solved the problem, why do you want to borrow a feed? What's the problem you are trying to solve?

The new bulb solved the dim main beam warning light. I was talking about tapping into a indicator feed wire or maybe the hazard warning switch. and running the wire to a bulb separate from the cluster circuit. And using that for the indicator warning light.