Dash lights not illuminating

[beerhunter]

Hi

I hope you can help, and apologies if this should be in the gauges section... I have recently bought a 1986 2.9 XLT, and the dash lights don't work.

The fuse and bulbs are fine. At the switch, there is power going to the blue w/ red stripe wire, which I understand is the feed to the dash lights. There is also power going to the red w/ yellow stripe, which I think is to the dimmer switch. So that all seems good.

I read elsewhere about the blue w/ red stripe getting shorted by people cutting in to the stereo wiring. There was/is no stereo in the truck, but sure enough, a previous owner had cut the wires and used connecting blocks to fit a modern stereo. In doing so, they have cut through the blue w/red (that is coming out of the same 4-wire bundle that contains the stereo permanent live and switched live).

I put a test light on it, and it lights/dies as I put the switch on/off, so the power is getting there. But where should this wire go, to get the power to my dash bulbs? I have been peering at the back of the dash, and can't see where it ought to be going...

I really hope you nice people can help, so I can drive at night...

Many thanks

 

[RobbieD]

I put a test light on it, and it lights/dies as I put the switch on/off, so the power is getting there.

Good troubleshooting so far. The blue/red is the illumination wire and it checks out as working from the light switch rheostat.

You'll need to pull the instrument cluster to do the same test on the same color wire at the connector on back of the cluster. If it tests good there, the issue will be on the cluster side. Could be corrosion on the connector terminal, and sometimes the flexible printed circuit will have a break. You can also test the bulbs with cluster out.

 

[beerhunter]

Thanks for the reply. I'll pull the instrument cluster plug after work, and see if anything is getting through there.

Thanks!

 

[beerhunter]

OK, so I pulled the instrument pod. There IS power to the blue w/ red stripe wire, that is live/dies as I work the light switch. So no breaks or shorts in the harness.

The bulbs all look fine but I changed half for new ones, as I had some - still nothing.

I cleaned the contacts on the plug and on the cluster - still nothing. I tried using the test light as a bridge in case it was still not connecting well. Still nothing.

I can't see any faults with the copper printed circuit. Can you suggest any tips for testing before I order a replacement? I'm in the UK so will need to pay import taxes and air freight, so would prefer to fix this one if I can!

Thanks!

 

[ekrampitzjr]

I had a '97 Escort that liked to have the multiwire connectors come loose from the back of the instrument cluster, even though they clipped in place. Check there first.

Edit:
Sorry, posted before your latest response.

 

[ekrampitzjr]

Check that dimmer switch. Maybe you have power going to it, but the switch is defective and isn't allowing electricity to the cluster. This is a surprisingly common problem with dash-mounted dimmer switches in American vehicles as they age.

On that Ranger you might have to replace the whole headlamp switch if the dimmer is bad, but getting that part should be reasonably cheap. The same thing for my father's 1992 Chevrolet Silverado pickup was less than US$30 IIRC, or about £20 + freight and duty if not stocked locally to you.

 

[beerhunter]

Thanks for your reply. It's a new switch, so should be fine. How would I test that the dimmer is letting power to the cluster?

I just popped back out and I see there are a pair of red w/ yellow stripe wires going to the other cluster plug (both sharing position 11). Is this the dimmer feed? Or is that just coincidence?

EDIT: I read elsewhere that red/yellow above are power for switched-ground indicators, so unrelated to my issue.

Thanks

 

[beerhunter]

UPDATE: I brought the instrument pod in to the house to have a good look at it. I connected a spare battery straight to pin 12 (+ve) and pin 14 (-ve), and it lit up like daylight / a Christmas tree / 4th July (your choice).

As there is power going to pin 12 on the plug, it 's looking like simply being a poor connection between plug and the flexi copper strip. I'll rummage and see if there's something non-conductive and non-flammable I can put behind the copper to press it more firmly against the plug pins.

Can anyone confirm if the other feeds to that plug use pin 14 for earth/ground? If they all share it (bearing in mind everything else works), then it's not a bad earth.

Thanks for your patience.

 

[ekrampitzjr]

UPDATE: I brought the instrument pod in to the house to have a good look at it. I connected a spare battery straight to pin 12 (+ve) and pin 14 (-ve), and it lit up like daylight / a Christmas tree / 4th July (your choice).

As there is power going to pin 12 on the plug, it 's looking like simply being a poor connection between plug and the flexi copper strip. I'll rummage and see if there's something non-conductive and non-flammable I can put behind the copper to press it more firmly against the plug pins.

Can anyone confirm if the other feeds to that plug use pin 14 for earth/ground? If they all share it (bearing in mind everything else works), then it's not a bad earth.

Thanks for your patience.

Try gently cleaning the contact area on the copper strip with rubbing alcohol (at least 70% strength) and a cotton swab.

Since you're in the UK, you might enjoy this flashback: this was a problem with Sinclair ZX81 computers with the optional RAM pack. The exposed contact area on the circuit board at the rear opening in the case, where you would plug in a printer or RAM pack, would oxidize. The accessory wouldn't function until the oxidation was removed. I had the Timex version here in the US, by the way...

Possibly the same principle applies with this Ranger.

 

[beerhunter]

Thanks, I'll give it a go.

Ha! We had one when I was a kid! It took so long to load, it put me off computer games, and I stuck to Lego. Possibly why I like playing with Fords now...

 

[beerhunter]

So... I cleaned those contacts til they shone. When I hooked the pod straight to a battery, the bulbs lit up great.

But when I put it on the truck, I now get a faint, faint glimmer. A multimeter tells me there's 11.5 volts going in at the plug (and to the stereo illumination wire).

Does anyone know where the instrument cluster grounds to? That's the only other thing I can think of, as I know the pod works, and I can see power is going in...

Thanks

 

[RobbieD]

Does anyone know where the instrument cluster grounds to? That's the only other thing I can think of, as I know the pod works, and I can see power is going in...

You're making good progress.

Look for ground G200. See the attached; hope it helps!

 

[beerhunter]

That's great, many thanks for the images. I'll have a look under the dash.

Can I ask - what book is that? It looks pretty comprehensive!

 

[Uncle Gump]

Go ahead and check the ground...

But don't forget that the panel dimmer could be faulty and dropping all the voltage across the variable resistor and only allowing them to illuminate really dim.

 

[beerhunter]

Go ahead and check the ground...

But don't forget that the panel dimmer could be faulty and dropping all the voltage across the variable resistor and only allowing them to illuminate really dim.

Thanks - how do I test for that? The voltage at the end of the wire touching to the back of the instrument pod/cluster measures 11.5v, so I thought that meant the dimmer switch was OK - as 11.5v are reaching the end destination.

N.B. I put a new switch on as I had read that they can be problematic. I appreciate brand-new parts can still fail, but it should be good...