For all of us that have driven these great cars there are some "blind spots", literally. One of these blind spots is in the dash lights. I think all of us familiar with these cars must admit that the actual dash running lights on the 123 chassis vehicles built from 1977 to 1985 are lacking. The reason for this lack of intensity is the way the lights work. There are two bulbs that send the light up through two separate light tunnels and then it is reflected back onto the face of the instruments. Some of the light intensity is lost in this transfer.
Problem & Solution
Common among these chassis:
If you remove your instrument cluster (if you are not familiar with this operation please see our "Instrument Cluster Removal and Component Replacement Guide") you will notice the light tunnels along the top of the cluster housing. With the cluster removed and the wiring still attached, you can turn your dash lights on and actually see light leaking through the cracks in these light tunnels. We discovered it is worth sealing these leaks by using aluminum tape as shown in this picture. The aluminum tape can take the extra heat from the lights themselves and will not deteriorate as other tape would. Two short pieces as shown are adequate. This aluminum tape can be purchased at almost any hardware store. It is the tape used to seat heater ducting in a house. If your cluster housing is badly burned or warped at the light tunnels tape won't help. You will have to replace the entire housing - no new parts are available - we have good used ones
Note: Do not expect a huge increase in light intensity. This modification will give a small improvement and depending upon how bad your cluster assembly is, you may or may not see a marked improvement in your dash lights. If your lights are still super dim you may have a bad dash light dimmer switch (poteniometer). Corrosion on the rheostat can prevent full voltage from getting to the light bulbs. Kent's Instrument Cluster manual will explain how to remove the rheostat switch and bypass it all together. Who ever needs to dim those lights, anyway?
Replace the bulbs with new. Old bulbs may work but over time they darken and lose intensity. You also may have a problem with corrosion inside your dash light dimmer switch. Watch Kent's new video on repairing dash dimmer poteniometers - see related products for more information.