electric issue: no instrument/clock/radio illumination when headlight is switched on

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flashgordon
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electric issue: no instrument/clock/radio illumination when headlight is switched on

Post by flashgordon »

Hello,

I removed the instrument cluster out of the dashboard to change a single non-working bulb.

When I removed the Panel into the Dashboard again all other illumination bulbs / FM-Radio Frequency and digital clock
went off in the same moment ... ( so did the under-dashboard illumination of 2WD-4WD and the ashtray illumination).

All signal lights in the instrument panel like the green turn signal lights and blue full beam light signal for example still work.

When I switch off head light, Radio frequency and digital clock are working again.

I checked all fuses. All OK.
I checked voltage in the bulb holder (with no bulb in it) --> 15 V -- OK

I also changed the dimmer-headlight-switch against a brandnew OEM dimmer switch yesterday. Unfortunately the problem is still there.

I looked, if I have dimmer in a low/off position, but this is not the case.
I thought of a burnt fuse or a broken cable, but FM-Radio Frequency and digital clock still work excellent when I switch off headlight.


One more observation:
when I switch on the headlights, the white instrument-panel-illumination-bulbs glow for a second or two (not very shiny/strong in my view) and then they all go out immediatly .
When I wait for 20 seconds or longer I can repeat this experiment and let the bulbs glow for a second.
When I wait less then 15-20 seconds for the next try, the bulbs don't glow at all.

I still assume it must have something to do with the headlights wiring/relays/switches...
I looks, that I loose voltage in the bulb holders, FM Radio and clock when I switch on parklight/headlight


Any idea what to check next?
Last edited by flashgordon on Mon Oct 16, 2017 1:37 pm, edited 1 time in total.
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REDONE
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Re: electric issue: no instrument/clock/radio illumination when headlight is switched on

Post by REDONE »

Just for snickers and grins, have you made sure your dimmer isn't turned all the way down?
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tgreese
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Re: electric issue: no instrument/clock/radio illumination when headlight is switched on

Post by tgreese »

So is this with the cluster in or out of the dash? I have not looked at the diagram, but its possible the lighting does not work unless he cluster is grounded to the body through the mounting screws.

Note also that it's a bad idea to power up the Jeep without the cluster connected to ground. The "voltage regulator" in the fuel gauge normally cycles on and off to "regulate" voltage to the gauges, and the "regulator" will not cycle without a ground. Many CJ owners know from experience that the gauges will burn out if you power up and the cluster is not grounded.
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Stuka
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Re: electric issue: no instrument/clock/radio illumination when headlight is switched on

Post by Stuka »

I have had this happen many times over the years. Have had to replace the dimmer before, but most of the time I just run it back and forth and it cleans off whatever corrosion has built up on the rheostat inside.
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flashgordon
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Re: electric issue: no instrument/clock/radio illumination when headlight is switched on

Post by flashgordon »

REDONE wrote:Just for snickers and grins, have you made sure your dimmer isn't turned all the way down?

absolutely right, had this situation months ago and then figured out the dimmer function....
And YES, I made sure


Just in case I attached a wiring diagram for the instrument cluster:

https://photos.app.goo.gl/mnidTDmAz8iE6euf2

Image
https://photos.app.goo.gl/P6PmVq8FdbChbou53

https://lh3.googleusercontent.com/qsKqC ... 01-h795-no
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flashgordon
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Location: Hamburg/Germany

Re: electric issue: no instrument/clock/radio illumination when headlight is switched on

Post by flashgordon »

Stuka wrote:I have had this happen many times over the years. Have had to replace the dimmer before, but most of the time I just run it back and forth and it cleans off whatever corrosion has built up on the rheostat inside.

YES, this is why I removed the headlight-dimmer-switch to make sure.
(there was indeed very few dirt around the rheostat).
But even the brandnew dimmer switch did not help so far...
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flashgordon
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Re: electric issue: no instrument/clock/radio illumination when headlight is switched on

Post by flashgordon »

tgreese wrote:So is this with the cluster in or out of the dash? I have not looked at the diagram, but its possible the lighting does not work unless he cluster is grounded to the body through the mounting screws.

Note also that it's a bad idea to power up the Jeep without the cluster connected to ground. The "voltage regulator" in the fuel gauge normally cycles on and off to "regulate" voltage to the gauges, and the "regulator" will not cycle without a ground. Many CJ owners know from experience that the gauges will burn out if you power up and the cluster is not grounded.

--> First, I probably should have disconnect the negative/ground battery. I see now.
--> I am not sure if I get the question above:
the "background" illumination doesn't work - wether if the instrument-panel is out of the dashboard
(what is neccessary to replace a bulb or to look for the wiring) nor if the instrument-panel is fitted into
the dashboard again.
I also dangled/wobbeled the instrument-panel and also the many cables behind the instrument-panel/in the dashboard
very carefully to make sure if this gives any reaction (glowing of the bulbs...) - but no reaction.
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