Hmm. I have a customer with a 2010 ram 1500. Keeps it immaculate condition. Complaining his dash lights will not brighten and sure enough he's right. Checked tech bulletins and nada. Rheostat is working. Lights just won't reach full brightness. Especially during daytime. Any ideas out there? Thanks.
BruceF

 

From the wiring diagram it appears there's what's listed as a "dim signal" wire from the headlight switch to the instrument cluster. It's not very clear from the wiring diagram is this is simply a current-limited control or if it's a digital (PWM maybe?) signal between the headlamp switch and the instrument cluster. The instrument cluster appears to have some "smarts" since the cargo lamp control is through the cluster rather than directly from the headlamp switch.

How did you confirm the rheostat is working, and are you sure it's actually a rheostat versus a digital controller? Do you have a high-end scan tool that might be able to display the desired brightness to confirm if it's the switch versus the instrument cluster itself that's the issue? The instrument cluster is on the CAN bus.

-Rod

 

Thanks for the reply Rod. As far as confirming if the rheostat is functioning properly, only observed that it dims and brightens. It just doesn't brighten enough to please the customer. I do have regular volt/ohm meters. But I am not familiar with the specs I am supposed to check for. Also I think the rheostat is a regular analog type, but not sure of that either. Just a guess. Thanks.....

 

If a scan tool can't access the brightness setting of the instrument cluster (not sure a 2010, or even a new one for that matter, has that info available over the CAN) then you're probably stuck pulling the cluster and checking the voltage to a bulb. Ideally you'd use an oscilloscope for that to help determine if it's PWM or just current limiting controlled.

Did you happen to ask the customer if the instrumentation lighting was ever bright enough for their liking since they've owned the vehicle, and if so, if anything was done shortly before they noticed the issue? Maybe someone had the cluster out and decided to replace all the bulbs as a favor but didn't use the correct part number.

-Rod