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Topic: Instrument Cluster Lights out (Read 6605 times) previous topic - next topic

Instrument Cluster Lights out

Hi all,
The illumination for my instrument cluster works normal, until I turn the headlights on. Then they just go black. Not illuminated at all. And its not just the cluster, the illimunation on the radio goes out too.

Is my headlight switch bad? I didn't really dig into it yet. Just drove it for the first time since getting parked for the winter.

Thanks,
-Kyle
1986 Ford Thunderchicken, 5.0 AOD w/ Shift kit,  354,XXX miles. 1-Family owned. Original engine+trans.
8.8 Disc Rear w/ 3.73 Posi. CHE Control Arms. '04 Cobra brakes all around. 2000 Cobra R wheels. Tubular front LCA's. MM Steering Shaft. Unlocked Speedo, Lowering springs, Eibach sway bars front and rear. Ram air intake.
 

Re: Instrument Cluster Lights out

Reply #1 –
Try wiggling the roller for dimming the instrument lights, see if they light up at all. It's probably worn or dirty contacts in the roller
2015 Mustang GT Premium - 5.0, 6-speed, Guard Green - too much awesome for one car

1988 5.0 Thunderbird :birdsmily: SOLD SEPT 11 2010: TC front clip/hood ♣ Body & paint completed Oct 2007 ♣ 3.55 TC rear end and front brakes ♣ TC interior ♣ CHE rear control arms (adjustable lowers) ♣ 2001 Bullitt springs ♣ Energy suspension poly busings ♣ Kenne Brown subframe connectors ♣ CWE engine mounts ♣ Thundercat sequential turn signals ♣ Explorer overhead console (temp/compass display) ♣ 2.25" off-road dual exhaust ♣ T-5 transmission swap completed Jan 2009 ♣

Re: Instrument Cluster Lights out

Reply #2 –







Hopefully you can see the pics I attached above this sentence.   I'm trying to send links from my Flickr account via my phone.

Flickr is NOT mobile friendly at all.

Your issue is almost assuredly the switch.  The little metal tab that connects to the switch housing and rubs on the rheostat dimmer wheel has a tendency to snap off on these switches.  The pics are a troubleshooting page and 2 pages of pinouts and tests for the switch to include testing for your exact issue.

Lemme know if you can or cannot see them.  I'll get on the laptop and work magic from there if I have to in order to make the pictures visible.  Yeahhhhh, edited for viewing through my Laptop.  Could not get it to work on my phone.  Not the forum's fault at all.  All blame is on Flickr.


If your switch IS in fact no good find an NOS one on Ebay.  The aftermarket parts store ones are WAY overpriced.  You can usually find NOS Ebay ones for around $30 USD.  I think AutoZone wanted over $100 for a Duralast brand one the last time I checked....
-- 05 Mustang GT-Whipplecharged !!
--87 5.0 Trick Flow Heads & Intake - Custom Cam - Many other goodies...3100Lbs...Low12's!

Re: Instrument Cluster Lights out

Reply #3 –
NOS one is here and has the part number:

https://www.classiquecars.com/thunderbirdelectrical80s.htm

Holy hell they are expensive so hopefully you can find one alot cheaper.

83 351W TKO'd T-Bird on the bottle


93 331 Mustang Coupe - 368 rwhp

Re: Instrument Cluster Lights out

Reply #4 –
Thanks for the trouble shooting diagram. Mine failed Step 5. The B2 -> I Connection. Otherwise, it passed all the other tests. Guess that means I need to  pull the cluster to see where that I circuit leads.
1986 Ford Thunderchicken, 5.0 AOD w/ Shift kit,  354,XXX miles. 1-Family owned. Original engine+trans.
8.8 Disc Rear w/ 3.73 Posi. CHE Control Arms. '04 Cobra brakes all around. 2000 Cobra R wheels. Tubular front LCA's. MM Steering Shaft. Unlocked Speedo, Lowering springs, Eibach sway bars front and rear. Ram air intake.

Re: Instrument Cluster Lights out

Reply #5 –
Check fuse 13.

Added some notes to the wiring diagram.

Re: Instrument Cluster Lights out

Reply #6 –
Update: Fuse 13 was popped. Replaced with a new 5amp fuse. Repeated the test above, and it still fails that step 5.

I'm thinking this might be an issue on the backside of the cluster.
1986 Ford Thunderchicken, 5.0 AOD w/ Shift kit,  354,XXX miles. 1-Family owned. Original engine+trans.
8.8 Disc Rear w/ 3.73 Posi. CHE Control Arms. '04 Cobra brakes all around. 2000 Cobra R wheels. Tubular front LCA's. MM Steering Shaft. Unlocked Speedo, Lowering springs, Eibach sway bars front and rear. Ram air intake.

Re: Instrument Cluster Lights out

Reply #7 –
Did the fuse blow again?

Re: Instrument Cluster Lights out

Reply #8 –
No it didnt. When jumping the I -> B2 connection the radio lights up, as it would when you turn the headlights on. But the cluster is still dark.
1986 Ford Thunderchicken, 5.0 AOD w/ Shift kit,  354,XXX miles. 1-Family owned. Original engine+trans.
8.8 Disc Rear w/ 3.73 Posi. CHE Control Arms. '04 Cobra brakes all around. 2000 Cobra R wheels. Tubular front LCA's. MM Steering Shaft. Unlocked Speedo, Lowering springs, Eibach sway bars front and rear. Ram air intake.

Re: Instrument Cluster Lights out

Reply #9 –
From your 1st post: The electronic gauges (LEDs) turn on with the ignition switch. That's good.
When you turn on the headlights, the "cluster illumination relay" switches the electronic gauges power to the headlight switch dimmer circuit ( fuse 13). This doesn't work.

The B2 to I jumper test should only turn on the illumination lights that come on with the headlights, not the electronic gauges (because the cluster illumination relay stays in the ignition switch power position).
All the stuff on circuit #19  LB/R wire in the diagram I posted should turn on.

Note: The B2 terminal of the headlight switch is labeled A in the wiring diagram.

If you plug the headlight cable harness back into the switch, will the electronic gauges  now work with the headlights on?

Re: Instrument Cluster Lights out

Reply #10 –
Nope, when I plugged the headlight switch back in, key on, turn the headlights on, the cluster is still black. And the fuse doesnt pop. Think I'll pull the cluster this week, since Ive had issues with it before.
1986 Ford Thunderchicken, 5.0 AOD w/ Shift kit,  354,XXX miles. 1-Family owned. Original engine+trans.
8.8 Disc Rear w/ 3.73 Posi. CHE Control Arms. '04 Cobra brakes all around. 2000 Cobra R wheels. Tubular front LCA's. MM Steering Shaft. Unlocked Speedo, Lowering springs, Eibach sway bars front and rear. Ram air intake.

Re: Instrument Cluster Lights out

Reply #11 –
I just started to have the same issue on mine. I replaced the headlight switch and the electronic cluster goes dim when the headlights turn on.

Re: Instrument Cluster Lights out

Reply #12 –
hi everyone,

I dove back into this issue and I made a discovery: the headlight switch gets really hot. Like hot enough that the coil for the rheostat was glowing. I'm not a genius, but if its getting that hot, that means its pulling a lot of current. So guess i'll be ordering a new headlight switch.
1986 Ford Thunderchicken, 5.0 AOD w/ Shift kit,  354,XXX miles. 1-Family owned. Original engine+trans.
8.8 Disc Rear w/ 3.73 Posi. CHE Control Arms. '04 Cobra brakes all around. 2000 Cobra R wheels. Tubular front LCA's. MM Steering Shaft. Unlocked Speedo, Lowering springs, Eibach sway bars front and rear. Ram air intake.

Re: Instrument Cluster Lights out

Reply #13 –
That'll help for the short term, but you should consider modifying the lighting system to have power for the LO-HI beams run through a couple relays, instead of through the switch.


Long live the 4-eyes!  - '83 Tbird Turbo - '85 Marquis LTS - '86 LTD Wagon

Re: Instrument Cluster Lights out

Reply #14 –
Quote from: 6hayden9 – on
I just started to have the same issue on mine. I replaced the headlight switch and the electronic cluster goes dim when the headlights turn on.
The electronic cluster is on full bright with the headlights off.
With the headlights on, it is adjustable with the dimmer control.