MC swap optimism

[Marc Swanson]

> So, the other two functions of the MF sensor are not necessary?
> One is for the autocheck overheat light, and the other for limiting
> boost if the car is overheating, right?  The third and only other
> function is for the temp gauge, which is covered above.


You got part of that right... The feature you are describing (the overheat
boost cutout) is actually a feature of those little single terminal temp
sensors that ground through the threads.  Can't remember which one controls
what but in any case you can actually interchange the 2 wires without any
noticable difference....

The remaining functions of the multifunction sensor are the AC cut-out, the
autocheck flasher (overheat), and it is also somehow tied into the low level
switch.  see http://marcswanson.ne.mediaone.net/Multifunction.html for
details... I traced out the diagram and simplified what the thing runs back
when I was sorting out the electrical issues.


> I understand eliminating the autocheck feature, since the whole
> rest of the autocheck goes away, IIRC, but isn't that boost
> protection a good idea? I live in Arizona, where it gets hot in the
> summer, like 115f or so.  Air conditioning weather, definitely

good luck with the air conditioning part.. it's pretty tight in there!  I
might have another go at fitting AC while the car is in the garage this
winter..
Also, you don't have to use the Multifunction if you want to keep AC.  Just
use the existing 4kq sensors that control AC cutout for that.



> > 2)Hack apart the drivers side harness and pull out only the
> wires that you
> > need (this is what I with the help of Huw Powell did)
>
> Kewl.  I like this idea.  Nice and streamlined.  Did you adjust the
> retained wires "lengths", as well as eliminating unnecessary wires?

not really, except for some of the ground paths I think. A whole LOT of wire
is removed in this process.  Keep some of it.. it comes in handy when you
want to custom wire stuff and keep it in spec with audi color codes ;-)

>  Did this involve trial fitting and trimming?

Not really.. I got it right pretty much on the first try.  I had some excess
in some places but I made that up by just looping the wire back on itself
before wrapping the harness with electrical tape.  I went through 2 rolls in
the process I think..


> Are crimp connectors recommended for this?  I don't want to
> rehash the solder vs. crimp debate.  I will likely be crimping and
> heat shrinking connections, absent compelling arguments against
> it.

Crimp is ok... I would highly reccomend something better than a $5 Radio
Shack crimper though.. I have my eye on this kit shown here:
http://www.rdent.com/pages/tools.html
On my car I started out with cheap crimp connectors and I had some funky
intermittant issues that were solved by going back and making nice solder
joints.  Moral of the story:  Do it right the first time!  In the process I
made an interesting discovery... The cheap $20 Radio Shack butane "portable"
soldering iron does a nice job!  I actually like it better than my
electric.... That and the heat shrink tubing from Radio Shack is junk.. I
found that the more expensive stuff found in the electrical isle of Home
Depot was much better (actually shrunk rather than the RS crap which just
melts....).


> > 3)Make up a harness completely from scratch.  Really.. now that I think
> > about it this probably might have taken less time.
>
> Yeah, if I was rich, I'd had Monster Cable or someone make me a
> wiring harness.  That would be for my 20vt ur-q, maybe with some
> progressive nitrous.

Not even going that far... but just taking strips of wire and making your
own harness.. I think it really might have taken less time.  There just
aren't really that many wires involved...


Later


-Marc-


/* +++++++++++++++++++++++++++++++++++++
+Marc Swanson                          +
+                                      +
+http://marcswanson.ne.mediaone.net    +
+                                      +
+87 4kcstq                             +
+85 4ksq  "the spare"                  +
+87 5ktq   donor (Parting out)         +
+++++++++++++++++++++++++++++++++++++ */