I have a 1999 Xk8 and recently the dash lights will intermittently go dim or flick on and off altogether while idling. Would this be the Alternator going bad?

Any suggestions would be appreciated.

Ken/Atlanta

 

Ken, odds are, you are looking at a bad pulse with modulator (ie, dash dimming switch). If that starts to go, you will see what you are seeing.

If you want some checks to verify the dimmer switch is failing, let me know.

 

Also have a look to see if the exterior sidelights are failing at the same time, that could be a bad headlamp switch.

 

Thanks for the advise folks. I guess I should start with verifying if the dimmer switch is failing.

thermo, can you let me know what to check for this.

Thanks again - Ken

 

Ken, when the dash lights go out, doe the lights on the radio and A/C control panel also go out? If so, then you are probably looking at a problem with the dimmer control module. If this is the case, let me know and I will give you some other checks to make.

First, put the ignition key in the column and then place the ignition switch in the RUN position (engine can be running or not). Next, place the headlight switch in the parking light position. This should turn on all the lights on the dash. Now, turn the dimmer switch all the way clockwise to raise the brightness as high as possible, then turn it back just a little bit to get it away from the switched on position. Now, with access to the back of the dimmer switch, do a voltage check of the yellow wire and of the orange/blue wire. Both of these wires should be at about the same potential (within 1 VDC). If not, then your dimmer switch is bad (assuming the dash lights are not lit). If these two voltages are within 1 VDC of each other and the lights are out, then this is almost garanteed to be a bad dimmer module. Verify the dimmer module is bad by access the dimmer module and checking the red/blue wires for atleast 11 VDC (anything above 9 VDC is good). No voltage, confirms bad dimmer module. If you do have voltage, then it is a problem with your instrument cluster.

You can also do a quick check and when the dash lights don't come on, turn the dimmer all the way clockwise (manually putting dash lights on their brightest setting). do the dash lights go to full brightness? If no, then this confirms a bad headlight switch (can also check the exterior lights to confirm). If the dash lights do go to full brightness and don't flicker, then it confirms your problem lies in the dimmer/dimmer control module.

Hope this helps.

 

I'd be getting out when the dash lights extinguish and looking at a sidemarker first.