I have wire under the dash of my 77 corvette five wire coming from the steering column.all light work no fire to dimmer switch

What is year--make--model of vehicle? Right now, I'd say, check the wiring circuit to and from dimmer switch. Could be dimmer switch, itself?

With wiring diagram, you can find proper color wire from steering column to low beam, everything on, see if voltage on that wire. I'm speculating that the dimmer switch controls voltage to low beam and not ground.

Under the dash, find wiring harness that goes into steering column, find proper color wire, test. If no voltage, when there should be, I think the problem is in the steering column, either wiring circuit or dimmer switch.

Yeah, anything in your steering column can cause problems. I haven't looked at a wiring diagram for your vehicle. Is your headlamp switch and dimmer part of the same switch or different locations?

Usually if I think the problem is in the steering column, I get at the wire harness under the dash where it goes into the steering column, Find proper color wire for what I'm trying to check, voltage or ground on whatever circuit. If headlamp switch is located separately from dimmer, then have to check voltage to and from steering column on proper color wires.

I don't like drl lamps at all, just my opinion. Especially auto lamps that you can't turn off, unless you pull a fuse.

You need to check the wires in the steering column. Take the column cover off, probably phillips-head screws, so you can see the wires. Somewhere the tilting function is putting pressure on the wires to the dimmer switch. It may be pulling loose a connection, just a fraction, to lose contact. You may also need a new dimmer switch. Or a multifunction switch if the dimmer switch is attached that way. The headlight switch is on the dash, isn't it? If it is, the headlight switch is not the problem, it is the wires in the steering column or the dimmer switch. If the dimmer switch fails, you will have no high or low beams, no head lights at all.

The same thing happens on my 2003 Impala. I found that my dimmer switch has an intermittent failure where sometimes the dash lights go out even with the headlights on.
If I wiggle the dimmer just right, the dash, radio, steering wheel, door locks, and every other light comes on (when the headlights are on). My fix was to mount my Garmin on the steering column in front of the speedometer so when the lights go out I know how fast I'm going. A replacement dimmer (or bypassing the current one and adding a resistor) should take care of it.

Check the bulbs, if OK replace switch.

1
Disconnect the battery to prevent ignition short circuits. Lower the steering column by removing the 15 mm column mount bolts. The column will drop safely down and the steering wheel rest in the seat.


2
Place the trouble light in a secure area under the dash and locate the ignition switch. The switch will have two black connectors that should be snapped firmly in place. The switch is easily recognized by the wiring harness that will have larger orange and red wires than other connectors. These are the main power supply wires. Carefully unplug the two connectors. Do not confuse these connectors with the lighting connector. The lighting connector is much longer, flat and does not have any large, power wires.


3
Locate the small, round, dimmer switch with a rod going into it. Leave it plugged in, but disconnect the mounting screws. The ignition switch shares a mounting screw with the dimmer switch. Remove two additional mounting screws holding the ignition switch in place. Gently pry out the switch rod that runs the length of the column to the key and tumbler.


4
Install a new switch by fitting the activator rod, mounting the new ignition switch with the screws and plugging in the wiring harness. Install the dimmer switch with the shared screw. Remount the column, attach the battery cables, and check the repair by starting the vehicle.

The wiring for the low beams would run not to the ignition, but to the dimmer switch. I don't know what color they are, but sounds like you are at the source of the problem, if the low beams quit when the column is let down. Pull the trim pieces off the steering column and examine the wires going to the dimmer switch. You may see some wiring insulation scraped off. It could be a bad dimmer switch, but check the wiring first.
Good luck.

Could be a couple of things. One would be that the dimmer switch has over time come loose and is now out of adjustment. Or the plastic piece in the column that pushes the rod that goes to the switch has broke. Or the switch is bad.

If you have replaced the switch, and it is still doing it it sounds like you definately have a short somewhere in your wiring. On the other hand if the dimmer is in the turn signal arm ( forward bright back dim ) the problem could also be there in the dimmer switch, such as a short being caused by that dimmer switch being faulty.Auto Zone and Discount Auto Parts both test a lot of your electrical problems for free, and/or may have some knowledge to more accurately pin point the problem. Not sure about Pep Boys or some of the other discount auto part chains.

Everything relating to do with the wiring is in the steering column, if someone has cut the wires going into the column and taped them back together in order to pull the steering column out for service the wiring needs to be replaced. the good news is if that is your problem it will cost you no more that about 30 dollars to fix it, the bad news is you have to pull the column to replace it. I hope that shines some light on it for you.