Dimmer switch for instrument display
 

My dimmer switch for all the instruments/gauges including stereo and climate controls appears to have a short in it. When I turn the dimmer the least bit either way, all lights go out, and then it is a process of wiggle left - wiggle right till they come back on. My question is, is this a wiring short/bad connection? Where would I start?

Re: Dimmer switch for instrument display
 

Well, it's a break rather than a short, but yes, your rheostat is toast. You need a new headlamp switch, which includes the dimmer rheostat for the dash lighting.

It might just be cooked but not broken; you could see if repeated turning of the knob back and forth will scrub the contacts clean, but what you're seeing is typical failure mode.

The switch usually replaces from the front, with some gymnastics required to get dash panels off first, swap the knob and shaft over to the new switch, that kind of thing. If you put your year and model in your signature, someone who's done it on your year of car can help with details.]

dimmer switch
 

Thanks, and I have just updated my profile to include my year. Sorry about that guys!! :oops:

Re: dimmer switch
 

Okay, here's a first draft of the Official Instructions on replacing the headlamp switch, as done on my '93 SSEi, which is probably the same as yours. It's distilled down from my diary on installing a remote starter, so if you find any obvious steps missing, let me know.

WillWren, if you want to plug this into TechInfo, cut-and-paste everything below this line...

93 Headlamp Switch Replacement

These instructions cover the steps required to remove and replace the headlamp switch from a 1993 Bonneville SSEi. They will probably cover the same process from model years 1992-1999, with some detail variations. You may need to improvise or figure out other details as you go. In case of major mistakes, notify me (acg_ssei) in the Bonneville.com forum.

Let's get the disclaimers out of the way first:

FOLLOW THESE INSTRUCTIONS AT YOUR OWN RISK. THEY ARE PROVIDED FOR YOUR INFORMATION ONLY, SUMMARIZED FROM FACTORY SERVICE MANUALS AND PERSONAL EXPERIENCE, BUT ARE NOT GUARANTEED IN ANY WAY. IF IN DOUBT ABOUT ANY STEP OF THE PROCESS (OR EVEN BEFORE YOU BEGIN), CHECK WITH A PROFESSIONAL MECHANIC.

The most common problems reported with headlamp switches are failed rheostats for dimming the dash backlighting. Wiggling or turning the knob may cause the lights to flicker on but not stay on reliably. The problem is a dirty or broken (from overheating) ceramic/wire-wrap rheostat in the headlamp switch that operates by turning the knob. Replacement involves installing a new, over-the-counter headlamp switch body; you should not need to special-order it from the dealer in most cases. The new part will be the switch body and rheostat combined, which plugs into the wiring harness and screws into the hole in the dash. The existing knob and shaft are reused, as is the Twilight Sentinel control ring on cars so equipped.

1) Lower Instrument Panel (IP) trim panel needs to come off first. This is the plastic panel surrounding the dash vents, Heater/Ventilation/Air-Conditioning (HVAC) and stereo, plus subwoofer if so equipped. Removing it will reveal the lower screws for the upper surround panel (the part containing the headlight switch and cigar lighter), and the upper screws for the lower steering column panel cover. Jam fingers into various edges of trim panel and pull firmly outwards until clips let go. You need to move cautiously here: just use fingers, not a screwdriver, and pull until a clip lets go, then move a few inches along and pull the next clip, etc. Work around the whole perimeter of the panel, and once all the clips are popped, it'll be loose. Clip at lower left of subwoofer control (if so equipped) may be especially nasty. Once panel is loose, reach behind to unplug subwoofer control wiring, and remove. Stow panel in trunk since we won't be reattaching it anytime soon.

2) Remove the headlight switch knob by pulling it out to the On position, and feeling around the back of the knob for the ear of a spring-steel metal clip that holds the knob on to the shaft. Press the ear of the clip inwards to the back of the knob (i.e. towards you) to release its grip on the shaft (a small flat-blade screwdriver may help here) and pull the knob off the shaft. Pull the Twilight Sentinel control ring off, if so equipped. Don't forget to turn off the headlights.

3) Using T-15 Torx screwdriver (or, in a pinch, an Allen hex key of the right size), remove screws around perimeter of upper trim panel holding headlight switch, cigar lighter and grille for HVAC aspirator tube (for cars with electronic temperature control). Panel comes off without a major fight; reach around back and unplug cigar lighter wiring. Remember that orange lighter wire is hot at all times, like now. HVAC aspirator tube (the tube emerging from the dash, behind a little grille, below the lighter on SSE and SSEi models with electronic climate controls) has temperature sensor in front, probably covered with major dust bunnies, so a quick snort with the shop vac should clean it all out, and maybe temperature sensor will respond a little quicker now. Stow the upper trim panel in the trunk so no one sits on it by mistake.

4) Last step of disassembly is to pull the headlamp switch itself. Remove three screws from headlamp switch, and it should come out the front, pulling its wires with it. You may find that the gauge cluster is slightly in the way. If so, remove all screws from the perimeter of the gauge cluster (those which hold down the white plastic ears of the gauge cluster housing), wiggle the cluster to the right about a half inch, and you should finally get enough clearance to weasel out the headlamp switch far enough to reach the wires behind it. Locate the locking tab(s) holding the wires on to the switch body and release the wiring plugs. As with the lighter, some of the wires on the headlamp switch are hot at all times, so go carefully.

5) To remove the knob shaft from the old switch, pull it out to the Headlamps On position, then look for a spring-loaded plunger sticking out the side of the switch body. Press that in, and it will release the knob shaft. (It only releases the knob when it's pulled out to the Headlamps On position first, _then_ you press the release button, not before.) Press the shaft into the new switch until it clicks.

6) Connect the wiring harness plugs to the new switch, test it, and reassemble.