1969-70 Mustang Instrument Cluster Lighting

By Erich Bozzer

When you turn your lights on in the evening and it's dark, do you have a hard time reading the gauges? You are not alone. These cars are now 35-36 years old* and the lighting is wearing out. There may be multiple reasons for the poor visibility. The technology for lighting the Instrument Cluster is called "Indirect". That is: the light from the bulbs reflects and bounces off the inside of the instrument cluster housing and onto the surface of the gauges. This differs from today's method of direct lighting where the light shines directly through the gauge surface. Direct lighting by design is brighter than Indirect. So, if you compare your newer daily driver to the old Mustang, the old Mustang will be much dimmer.

There are four things that affect lighting in these clusters: 1) the reflective surface inside the housing, 2) the blue filters 3) the bulbs 4) correct voltage. To improve your lighting start by checking that the reflective surface is clean and free from scratches and discoloration. You may have to paint the surface with a flat white paint. Flat is better than gloss because of its diffusion properties. The blue filters may also have to be cleaned if dirty or even replaced. The heat from the bulbs softens and deforms or melts them over the years. Filters like these were used in numerous Ford cars up into the mid 80's. The newer ones are slightly shorter and have a different mounting style, but can be made to work in a pinch. You can even delete these filters if you want a new modern "white" look to your gauges at night, and it will be much brighter! By the way, there are red filters in the '84-'86 Mustangs if you want to be unique. Now lets talk about the bulbs. The original bulbs are the industry standard #194. They are 2 Candle Power (CP), 3 watt bulbs: 0.25 amps @ 12 volts. As a side note "watts" is not a measurement unit of brightness. It is a unit of power, which equates to heat. Candle Power (CP) is a unit of brightness. We are so used to seeing watts meaning brightness in our household bulbs that the misunderstanding is common. If you look on your package of bulbs next time you buy home light bulbs you will see that they are also rated for Lumens, which is another brightness unit. OK, back to #194's; they use the tungsten technology, which does wear out with time. The #194 bulb has a life rating of 2000 hours (about 60,000 miles) to half brightness. So chances are you will need new bulbs in the old 'Stang. Examine your bulbs, if they have any trace of silverish coating on the inside surface of the glass, they need to be replaced. All this can be good but if you do not have full battery voltage at the bulbs you will never be bright enough. With a voltmeter, measure the voltage right at the bulb on the back of the flexible circuit. It should be just a few tens of a volt less than what is measured at the battery. The causes for lower than normal voltage are: defective rheostat or not turned to full bright, loose or corroded connector pins to the instrument cluster, loose bulb connections to the flex circuit or loose or corroded ground connection; located to the left of the instrument cluster screwed to the lower dash panel steel near the dash to body mounting bolt.

Now that you have a nice clean white reflective housing, clean and clear blue filters and new #194 bulbs and you still want more?! If you don't like the idea of removing the blue filters to get brighter, there are a couple other bulbs to try. The 2825-W5W is a brighter bulb. In fact it is twice as bright with a brightness spec. of 4 CP. But, this doesn't come for free. It is a 5 watt bulb; drawing 0.4 amps at 12 volts. It will get hotter! This will only be a problem if long stretches of night driving are done. If you have to drive a long time with your lights on, just turn the brightness down with your rheostat dimmer. This will save melting the blues filters. Another price to pay for the 2825 is its short life: only 300 hrs. I saw these bulbs at my local AutoZone for $2.99/pair. Another bulb to try is the bulb that was developed for the 1985-86 T-Bird Digital LCD Instrument Cluster. These are 2.5 CP, 3-watt bulbs. They use Xenon gas technology so they have a whiter light than the standard #194's. The #194's are mostly yellow. There is more blue light in the T-Bird bulb than in the #194 bulbs. When they shine through the blue they will be brighter looking. These are very expensive bulbs. New from the Ford dealer they cost over $12.00. The part number is E5SZ-13B765-C. You may want to try to find some at your favorite junkyard. There are only 2 bulbs in the base speedo. module of the T-Bird and 6 bulbs in the Optional full digital cluster. Your '69-'70 Mustang needs 8 bulbs for the illumination. Make sure you get the bulbs with the orange colored socket. A similar bulb to the '85-6 T-Bird is the bulb used in 1988-94 Lincoln Continental LCD and 1989-93 T-Bird Instrument clusters. This bulb is only 2.0 CP but is still very white with more blue light so will look brighter. This also has an orange colored plastic socket. The part number is E89Z-13B765-A and cost about $12.00. The visible difference between these two bulbs is the shape of the glass. The E89Z is rounded like the #194 and the E5SZ looks like the tip was pinched off.

Now you have a few options to make improvements to your dim Instrument Cluster.

* Article written December, 2005. Basic paint, bulb, filter and voltage information applies to Cougars and other Ford cars of that era as well. Number of bulbs may be different.

Since this was written new Light Emitting Diode (LED) technology has come out featuring bright LEDs with low current draw. Instrument cluster upgrade kits are available from various Mustang parts suppliers. An example of one kit was discussed on our messageboard. Other discussion.