Dash lights dim on Mustang

The dash lights on my 73 Stang are dim even when I have them turned all the way up. The gauges are barely visable at night. The dimmer function on the headlight does work but it just goes from dim down to nothing. At first I thought it may be a few bulbs blown in the dash but the radio and heater controls glow at the same level so I don't think it is that. Any ideas?
Thanks,
Danny

Is this at an idle or when you are cruising or both?

It could be your voltage regulator is bad. Or the drive belt for the alternator isn't tight enough and it is slipping. Or possibly the alternator is going south. Or even possibly the engine ground is corroded or broken.
[addsig]

Take your dash out, remove all bulbs, being CAREFUL not to tear the banded circuit that holds them in, and give ALL contact points a good steel wooling to remove corrosion! Did this myself on my gf's 72 mach and it worked wonders! You may need to replace some older bulbs too, as some of the ones I saw were still like 60's bulbs, and the tech just wasn't there to make em bright? [img]/phpBB/images/smiles/icon_razz.gif[/img]

I've also seen where the actual 'rheostat' (located on the headlight switch/internal), is corroded/bad, necessitating replacement of the headlight switch for that problem.
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(a quick test is to bypass the circuit, (headlight illumination), at the switch, and see if the brightness comes up to par).[img]/phpBB/images/smiles/icon_wink.gif[/img]
[addsig]

I just read a couple of days ago at another site that someone found a fix for the 71-73 mustang dim lighting problems. He said he took out the bulbs and painted them with blue paint and that fixed it. He said he took his mothers car that had 35000 miles on it apart and also his to compare and found that the blue cups in the cluster were faded in his car and his mothers car the blue cups that reflect the light were bright and the blue paint worked very well. Someone said blue bulbs are available at the auto parts stores.


Blue Fastback

I checked the voltage at the instrument panel fuse and got 10.5 max. When I used a jumper to bypass the headlight switch and shoot a straight 12 to the panel lights they got somewhat brighter but it wasn't the huge improvment I had been hoping for. An investment of alot of time and a little money should eventually lead to a solution for this problem. If you get any more ideas let me know.
Thanks,
Danny

There is also a voltage regulator attached to the back of the dash panel. These go bad and cause all kinds of strange things. Usually the gauge readings go squirrely. These are common and available from Ford. I think the last one I bopught was $7or$8.

Did you take a voltage reading when you held the rpm's around 2000? I believe the voltage should be closer to 12.8v-14v when the alternator is charging correctly.

It does sound like a low voltage problem related to the alternator/voltage regulator.....
[addsig]

I guess I should have mentioned that the car was not running at the time I took the readings.....
Danny

In addition to the items already mentioned. Don't forget to check the ground connection for the instrument panel. If there is any corrosion on the ground side of the circuit that will also cause dim lamps as corrosion adds resistance into the circuit and lowers voltage to the bulbs.