Heater fan switch has been getting so hot as to fill the place with burnt-electronic-smell... it was probably bound to happen, the biggest switch I could find that day was 20A and the blower-fuse is 50(!)A. Also, inductive-loads, arcing, etc...

So ripped out the dashboard-cover at some late hour, and leaving it 'till payday for a better switch. 

[Note to self: heat-selector-switch controls blower-relay, speed-switch *directly* switches in and out series resistors with plausibly 30A blower motor. This is the third failed switch. Maybe turn heat *off* before adjusting speed.]

[Also, obviously, thoughts on relays or even PWM.]

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Meanwhile, a few long-running project-ideas for while the dash is open...

Hacked the cheap FM/AM-only stereo for AUX-in, can finally play my own tunes [and GPS directions]! [Yes, I have an FM transmitter. It sucks, and my phone's *really low* max volume made it far worse.]

Stereo was a bit quirky, I think it's Class-D, and apparently that means the two identical large-ish caps near the [speaker] connections *aren't* for the speakers. None of the chips have datasheets, wiring is crazy [rear speakers not implemented, so they ran front-right - signal trace to rear-right +, first, shorted that with rear-right -, then fed that to front-right - via two parallel 0-ohm resistors, and such-like. 

Ultimately found two parallel traces with large series surface-mount caps originating under the tuner-circuitry's shield heading to unknown chip which is connected to both the presumed processor and the presumed amp, presumably for things like equalization.

Oddly, it has four parallel traces leaving it through four of the same series caps, to the amp. Prb also handles r/l and f/r balance... if f/r was implemented. But why bother with wiring caps to unused outputs? Or maybe it's differential, hmmmm... plausibly isolating amp power/gnd from the rest... hmmm...

Also oddly, amp looks identical [sans different markings] to the other chip with the big caps... am thinking it's for power.

So, it was a crap-shoot, but I tombstoned the caps and wired up the phone and, yep! 

Managed *just enough* space for a dpdt switch [on-on-on, weeeeeeee!], and dangling a headphone plug, 'till I'm up near storage again.

LOTS of debate about how to shield... ultimately the sun was going down, losing light to work by, so decided on two twisted-pairs of wire for each r/l signal pair. All "shields" tied together at the chip's ground, but at the switch they're N/C.

The aux input is split kinda like a mini-plug to rca cable, each signal "shielded" with a twist, then the shields tied together at both ends [one at mini-plug, one at the switch] then a single ground-wire down to that same point on the chip. Trying to prevent r/l crosstalk...

But, sure-enough, with no source connected to aux, and volume-maxed it definitely picks up the radio... not sure if it's a shielding issue, or inside the switch, or...

But *WAAAAY* better than that FM transmitter, which was too quiet, staticky, and picked-up ignition-firing, and even worse when the phone was charging.

On that note, not sure what to do about charging simultaneously... definite ground-loop-ish issue, seems to pick up the dc converter's switching[?]

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Other while-dash-open ideas include:

12V banana plugs, ferchrissakes.

[Maybe 5V and-or built-in USB? + switch!]

Heater only does recirc with AC running, by stupid design. Add AC cut-off switch

Aux Lighter-outlet melted-to-short. replace!

Surely more... blanking.

Oh, stereo power-source selector-switch!

Also might look into cleaning duct-work.

Still... surely more...?