Climate Control switch illumination problem

KENNYASH

MEMBER
2011 FORD E-SERIES VAN
5.4L
V8
2WD
AUTOMATIC
146,000 MILES

E-350 passenger van.

Wife put jumper cables on backwards 3 years ago, and blew a couple of fuses. I replaced the fuses and all was well except the illumination behind my climate control knobs. (And also the illumination behind the blower speed knobs, and headlight switch/knob and dimmer switch) All instrument cluster lights work, radio lights work, power outlets work, all switches work. Dimmer control works for the radio lights and cluster lights. But I get no illumination behind these switches/knobs no matter what I do.

I’ve checked every fuse in the passenger compartment fuse-panel, (#10 was blown, but replaced), and I’ve visually checked every one of the fuses in the fuse-box under the hood. All good.

This has plagued me for 3 years, and it’s high time I figure out what’s keeping it from working! I pulled the bezel off the dash, and checked the 2 bulbs behind the climate control knobs. Both looked good.
the only other thought I had was if those bulbs were in series with the bulbs behind blower switches, and headlight switch illumination!

But beyond this, I’m stumped.

any suggestions on things to try?

(Photo shows controls, with headlights on, dimmer at max. No lights behind the switches/knobs)

1 Reply

STEVE W.

MECHANIC
13,560 POSTS

Do you have any steering wheel controls and do those light up? From the wiring it looks like it could be a failed FET backlight driver inside the smart junction box (aka fuse and body control box). It powers the LEDs in all of those locations. That isn't a serviceable part in that replacing it requires replacement of the smart box itself. To do that you need a scan tool that would allow you to transfer the information in the current unit into a file, then once the replacement is installed you upload that, then do a few relearn procedures on the TPMS system and reboot it. The physical replacement is the easy part. Remove the three nuts and 7 wiring connectors after disconnecting the negative battery terminal. Remove the unit, install the replacement and upload the files to make it work. In this instance you cannot use a used part without erasing it's files first and that isn't possible with most scan tools or programming options.

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