Sunday, September 16, 2012

Redoing the dash wiring

When I got the van, the prior owner told me the dash lights didn't work. I asked if whether they'd faded out or died suddenly, and he said they'd just died suddenly. So I figured there was a fuse that was blown, and the Bentley manual told me there was a fuse involved in the dash lights. But I sure couldn't find it. It wasn't mentioned in the fuse panel's list of fuses, either. So for one of my projects, I decided to replace the lamps in the dash with LEDs. This was unlikely to help, but I figured it couldn't hurt. Replacing them required pulling out the instrument cluster, which is actually pretty straightforward. When it was off, I spotted a fuse hiding on top of the fuse block that isn't mentioned in the cover. I replaced this, and all of a sudden, most of my dash lights were working. Success!

Except I wasn't done yet. When we took Kurt out for his second trip last weekend, I was futzing with the heater and the dash lights flickered off. And, about a month after we got the van, I'd been trying to figure out an unrelated problem when I spotted loose wires hiding behind the ventilation controls. Here's what the wiring looked like behind that. Note there are three dangling, stripped wires in view, and a fourth out of view.

Two of these are ground, so not dangerous, but silly. The last, the blue/grey wire with electrical tape covering it, is switched with the dash lights. When the dash lights are on, this showed +9V. The end was stripped, so turning on the dash lights could mean a short, followed by a blown fuse. And see the silly twist connectors? The van's full of these wherever the prior owner did work. I don't like 'em because of their tendency to fail with time, at least if they move around.

Another thing that was bugging me was the cigarette lighter. It was dangling half out of the dash, and didn't work. Here's what the wiring looked like when I tugged at it:

I swear I didn't enhance the ugliness for effect, this is just how it looked. Yep, two more twist connectors, and a cut wire whose use I didn't immediately guess. The brown (ground) wire coming out of the twist connector was disconnected. One side of the red (12V) wires went to the glove box light, and the other side was the source. Or, it should have been. But according to the ohm meter, it and the ground were one and the same. Glad it wasn't working! At least the prior owner did one thing right:

He had an inline fuse in the source. Good thing! I wonder how many of these he blew trying to figure out his short? (Again, I note the repeated use of twist connectors.)

So I rewired the source for the stereo and the cigarette lighter, and replaced the lighter. The new lighter came with a light that switched on with the dash lights. Ah hah! Here's the reason for the cut blue/grey wire both in the old lighter and hidden behind the ventilation controls. Here's my new cigarette lighter and glove box light wiring, before I mounted them into the dash, with apologies for the terrible exposure:

I kept an inline fuse, because the source circuit for the cigarette lighter is shared with the stereo, and with luck causing a short across the 12V receptacle would blow this fuse before damaging the stereo. (It has its own fuse, too, but I decided to play it extra safe here.) I went with a blade fuse just because I happened to have extras of those. I used a tap splice to provide 12V to the glove box light, figuring it'd serve as a canary to tell me if the fuse was blown.

Finally, here's the dash all put back together:

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