i drive a 94 bronco the 4x4 and low rang are buttons.and a little light lights up when they are engaged. but i noticed that the low range light is constantly on. but its not as bright as the 4x4 when the 4x4 is engaged engaged. and low rang will not engaging at all

You don't need a light to tell if you are in LO range, you will be able to tell that by the unusually high RPMs when you start to move the truck. The light glowing dim may be indicating that you have something wrong with the switch that turns it on.

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Also when you romp on it in low range it'll usually jerk your head clean off your shoulders! You'll go from 0-5mph in no time at all and the engine will already be at redline!

God I love that. Jeez, imagine driving one of these things in low gear around town for a week? You'd have to fill up every hour or two.

Are you noticing the low range light being dim in 2WD or just when the truck is in 4X4. The dimly lit light could just be light coming from the bulb that lights up when the truck is in 4X4 Hi.

its on all the time wether its in 2 wheel or 4 wheel drive

1356 Electric Shift Motor Troubleshooting & Repair - BEST PROCESS!
Source: by Dustin S
read it all; esp.;
No Range Shift

If the vehicle won't shift into 4L, check the speed sensor and the transmission interlocks (neutral or clutch in). Also check the 4L switch (C3) to see if the module is getting a signal. Be sure to check for corroded connections.

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Indicator Lights Don't Register the Correct Information
If the lights are on all the time, look for a short to ground. Also check to see if the shift control module is activating them all ... this is a malfunction.
If the LED lights, in the buttons, remain on all the time, first check to see if the dash lights are also on. If the dash lights are not on, this means that the dash lights have burned out. The LED lights are on because a low current is still passing across, enough to light the LED.