96 850 Turbo Dash illumination lights dead

mustang_man298 · Post by **mustang_man298** » 13 Oct 2015, 11:49

My apologies if this has been discussed somewhere before, I wasn't able to find this in a search.

A little history first, back when I got the car a little over a year ago, they were out, I searched and found the dimmers are known weakneses. I tried the "jumper" test with the brn/org to pink wire, blew the # 35 fuse, however after spraying contact cleaner into the slider on the dimmer and working it a bit, the lights came to life.

Flash forward, here we go again, suddenly no dash lights. Same thing with the jumper test again, this time I put a VOM from the pink wire to ground, reads 0.2 ohms. To me that seems like a short, by my calculations we use 3W lamps in parallel, so total circuit resistance should be equal to any one lamp, 3w at 12v equals 48 ohms. (Watts div. by volts = amps, volts div. by amps = ohms) Sound like I'm on the right track here?

I tried another experiment, using the dimmer rheostat section from a Ford truck headlight switch as an attempt to regulate current, I jumpered the brn/org to pink through said rheostat, did not blow the fuse but the large ceramic disk got super hot very fast, and turned the rheostat winding blue in seconds. (I do not believe I saw anything happen with the dash lights either) As much as I dislike the thought, I'm thinking I need to open the dash up, anyone have any other thoughts or know what that circuit's resistance should actually read?

Post by **JDS60R** » 13 Oct 2015, 11:51

Common issue - dimmer slide switch failure. Just hit the junkyard or replace new.

There is a really good post around somewhere - I'll report back if I find it.

mustang_man298 · Post by **mustang_man298** » 13 Oct 2015, 11:59

I may be overthinking this, but my slider tests out good, with it desoldered from the ribbon cable, it reads 154 K-ohms on the two outer terminals, and a solid steady 54 ohms up to 154K from the center terminal to either side as I slide it. It may be that the electronics on the board in the switch have failed, but I am concerned it may have been caused by something else in the dash because of my other findings.

mustang_man298 · Post by **mustang_man298** » 14 Oct 2015, 17:18

After some frustration yesterday, I went ahead and bought 3 dimmers from Pick-N-Pull this afternoon, I figured my chances were good that way that one would work (since I live 22 miles out of town). None of them appear to make the lights work, best I can tell with a comforter over the car windows and cardboard over the dashboard, thoughts?
Also the switches came from a variety of years a little above and below mine, same physical switch, but I noticed all 3 were made by "SWF" with a part # 1390065 & a Volvo marking, OE replacement parts? The original was an Alps 9162467.

mustang_man298 · Post by **mustang_man298** » 20 Oct 2015, 16:23

Now that I finally had some time again & good weather, I revisited the problem today. Decided I would take an easier approach than removing the whole dash cap & going deep into it right off the getgo. The previous owner had installed an aftermarket radio, leaving a hole open above it, so I popped out the climate control module & unplugged it. Still no lights, and no voltage on the pink wire to the black (chassis ground). I remembered I'd had the radio out a few trips prior to this issue diagnosing a non working antenna. I pulled it back out, he had used a pigtail adapter so as not to butcher the dash wiring, but had twisted the adapter wiring to the radio wiring and used electrical tape on it. I found a bare ended orange wire that went back to a pink dash wire @ the plug. 12V with key on and lights on, and with the wires out in my lap I now have dash lights again! Needless to say the wiring was corrected before getting stuffed back in.

I went ahead and tested the extra dimmer switches I got from the yard while I was in the dash, all 3 spares work great. So, if anyone needs one of these dimmers, PM me, I have 3 tested known good working ones, I paid $7 each @ the yard, plus your shipping.

Post by **erikv11** » 20 Oct 2015, 18:45

mustang_man298 wrote:.... The previous owner had installed an aftermarket radio, ....

Ding, ding, ding!

Great job figuring this out, sorry for the lack of input. Your post reminds me that the first question when there are dash electrical gremlins is "Did anyone install any non-factory accessories?" Love that 20-20 hindsight.

mustang_man298 · Post by **mustang_man298** » 21 Oct 2015, 17:14

Indeed. It was even one of the first thoughts through my head that I should suspect it, I dismissed the thought since it had been trouble free for 2 years, other than getting no radio reception (bad antenna cable)

Brahms · Post by **Brahms** » 23 Oct 2015, 10:33

My dash lights were out for a while, I later figured out that it was related to me replacing the broken stock stereo with a new stock stereo. It sounds like the same thing that happened to you.

This is probably odd, but I drove it for quite a while at night without dash lights, so that I rather grew to like the dark dash, so now I often leave them completely off. Yes, I know - I cannot see the MPH and all that. All I can say is that when I see the new cars with all the LED readout and maps and everything it really does not surprise me that drivers are so distracted.

mustang_man298 · Post by **mustang_man298** » 28 Oct 2015, 04:50

I know exactly what you mean. The 850 is the wifeys car, we also own a newer Prius I drive, the display with all its changing & moving icons in the corner of your eyes as you drive can become quite annoying at night.