I have a 1988 Buick cetury. When I turn on the head lights the dash board 
lights go out and so does the radio light. When I turn off the head lights the
dashboard and radio lights come back on. I have changed the dimmer switch as 
well as the headlight switch. What can be the problem?

Hi there!

We used to have an '87 Century that gave us the same trouble.  Replacing the 
headlight and dimmer switches didn't solve the problem for us, either, but 
replacing the alternator did.

This does not necessarily mean that this is the root of *your* Buick's problem, 
though.  There are some less expensive possibilities.  Have you had a look at 
your fuses and your ground wires?  Corrosion on any of those can cause 
problems, as can loose wires in the dash.  

The USENET newsgroup rec.autos.tech is a busy and well populated group devoted 
to car repair questions.  Posting a detailed description of your problem there 
may very well net you complete instructions for repairing your car for free!
[http://groups.google.com/groups?hl=en&group=rec.autos.tech]

I also located a free, comprehensive Buick owners resource, The Buick God 
Network.  The site offers numerous Buick FAQs, including repair FAQs, and a 
message board where you can get repair advice from other Buick owners.
[http://www.buickgod.com/]

A search through archived Car Talk columns at Car Talk 
[http://cartalk.cars.com] on the words "dash board lights off" turned up an 
article which, while not specifically referencing a Buick, suggests that a 
similar problem may be caused by a bad fuse.  Tom and Ray advise taking *any* 
electrical problem to a professional, however.
[http://cartalk.cars.com/Columns/Archive/1992/September/05.html]

Some car repair questions can be answered at the DIY (Do It Yourself) Network, 
which offers a project index, as well as chats and message boards.  You can 
find the Automotive section here: 
[http://www.diynet.com/DIY/categoryHome/0,1018,AUTO,FF.html]

The DIY Network also offers online access to Chilton's manuals, long considered 
*the* car repair manuals.  There is an annual subscription fee, but this may be 
to your liking if you prefer repairing your car yourself and don't mind a small 
fee for step by step instructions.
[https://chiltondiy.com/]

If all else fails and you decide to take it to a mechanic (as recommended by 
the Car Talk Guys), you can get a recommendation for a good shop in your area 
by using the Mechan-X Files at Car Talk.
[http://cartalk.cars.com/About/Garage/intro.html]

I hope you find this information useful.  Good luck with your repair!

How old is the alternator?  It might be that the alternator isn't providing 
enough of a charge to charge the battery and thus when your using the 
headlights and everything else, the required current isnt available.

Do you hear a clicking sound when you try to start the car?

Are the headlights OEM?

faulty wiring is the only cause here. must check your circuitry.

I had the same sort of problem once, it turned out to be an earth/ground fault. 
Check out all ground leads to car chassis for bad or corroded connections, 
especially around the headlight/s unit.

Two additional sources of infomation for your problem may be found at
www.batauto.com and the car question booth at www.cartalk.com. At each
website automotive mechanics answer questions.

Of the comments you've received, I'd lean to the faulty ground. Those
are not aways easily found. I'm assuming when you replaced the two
switches that
included the one used to adjust the intensity of the dashboard
lighting. If not I would check that component. Factory shop manuals
can be found from
time to time on eBay if you wish to purchase one. Many autos have a
circuit involved that automatically dims the dashboard lights when the
headlights are activated to avoid distracting the driver at night.
Perhaps yours is completely killing the voltage.

The factory shop manual for the body wiring will have a diagram of
that circuit. Most dealers won't mind you looking at their copy of the
manual. If all else
fails that may be your last chance at diagnosing the problem to fix it
yourself.

Good luck!

Sounds like a dead battery or corroded battery connections. Does it start?