Dash mounted switches not lighting up well

[waltmail]

Okay, where to start? Most of my switches, if not all do not light up at night (with headlights on). Makes my memory work overtime to find the switches. Is this controlled by the headlamp main switch or??????????? Any ideas for resolving this issue. I tried Ronnie's tutorials but did not find anything related. Tried the "search function" and it hates me.

[Dashmaster]

This is a tread from the problem that I had on my 88.

http://forums.aaca.org/f116/automatic-dimming-question-saving-override-daylight-388927.html

[DAVES89]

Do they light up when you get "the show"? If they do the inverter is probably bad. If they are dim, then what has happened is that your backlight illuminecent strips in the switches are going bad. That means you will need to replace the switches as to date there is no replacement strip.

I forgot about the photocell. Thanks Dashmaster

Edited May 5, 2015 by DAVES89 (see edit history)

[waltmail]

Do they light up when you get "the show"? If they do the inverter is probably bad. If they are dim, then what has happened is that your backlight illuminecent strips in the switches are going bad. That means you will need to replace the switches as to date there is no replacement strip.

I forgot about the photocell. Thanks Dashmaster

Activated"the show" with the test button. "Rear window def" and "defroster" light up on test. Headligh/Park lights switches do not light on "test", but do light up when activated. Shifter position does not (could be burnt light bulb in unit???? ). Dimmer control does work. Cruise control light and hazards light when activated. Any ideas?

[KDirk]

A few of things here. First, run the diagnostics on the photocell as referenced in the thread Dashmaster linked above. If the readout does not show it indicating darkness when fully covered to prevent exposure to daylight, then the photocell is almost certainly bad. The headlight, wiper, window, mirror, console switches and gear indicator backlighting will not illuminute if the photocell is bad as the BCM will always think it is daylight out. The backlighting is disabled when the car thinks it is daylight out. A failed photocell usually spoofs the car into seeing a daylight reading.

Second, you can use the override in diagnostics to test and see if the two inverters (dash and console) and the EL backlighting are functional. If any of the switches or indicators that are EL backlit fail to light when the override is active, then you have a problem with either an inverter, one or more EL strips or the wiring associated with the the backlighting circuits.

Third, the test button on the cluster does not trigger the full lightshow as would occur on entry and closing the door (assuming that is working). This only tests the digital display on the cluster so will have no impact on testing the switch backlighting.

Fourth, the amber color LED spot illumination on the headlamp and wiper function switches (red LED on the hazard button) works independently of the backlighting, the two have nothing to do with each other so don't let those confuse the issue when troubleshooting.

The absolute first thing you need to determine is if the photocell is bad. If it is, you will not get any of the switch backlighting to work save for using the override. Once you are sure the photocell is good (or have replaced it after determining it is faulty) then any other faults in the backlighting circuit can be addressed. The photocell is the key component as it is the one common part that can sink the whole system. Diagnostics makes this easy to check.

For the record, both my 88's had bad photocells and my 91 convertible is showing signs of failure (poor sensitivity) so it is about to be replaced while I have the interior apart for other work. My point is to emphasize that this is a common failure and it seems many others here have had the same problem.

If you don't have a factory service manual, ROJ covers the diagnostics for this.

KDirk

[waltmail]

Thank you sir. If you saw my other post on the dome light, would you know the answer to that one. I appreciate your knowledge and input.

[waltmail]

Just found the relay mounted in the trunk on the antennae mast. Should take me a few hours to figure out how to pull the relay. So far, it is a no go.