Re: Re: Re: (forget it) Now Heated Locks

[kirby.a.smith@lmco.com]

Brett Dikeman <brett@arthur.malebolge.com> wrote, in part:

[snip of heated washer nozzles stuff]
   Hmm..If I go with that, I'll have to retrofit lock deicers as well :)
   (THAT would be useful.  Stupid locks kept freezing up until I finally got
   disgusted and completely dissassembled the entire locking mechanisim,
   including tumbler.  There was all sorts of crap in the tumbler, but I fixed
   that.)
   
   Anyone who's seen the lock deicers know how they work?  Is it just a
   "jacket" that wraps around the tumbler?  How easy would it be to kludge?

Well, I'm progressing on that project now for my 1988 90q.  You need the control
module, the correct door handle with attached microswitch, and the heated 
tumbler assembly.  You can wire to the vacuum lock assembly for power.  The 
tumbler heater is a potted resistor sunk into a rectangular frame molded onto 
the tumbler housing.  The resistance of the resistor is very low, so building 
one yourself may be problematical (see below).

I expect that parts for any 90q between 1989 and 1991 will fit my 1988.  So far 
they look OK.  Need to get into the door again.  I don't know how well various 
5000/200 assemblies will back retrofit their respective models.

The heater resistance is so low (0.5 ohm? don't have the value with me) that the
current load should be very high, and the lock should heat up very rapidly.  Why
doesn't something melt if one keeps holding the handle.  Well, the control 
module has a button on it for test.  At room temperature, pulling up on the 
handle does nothing unless the button is pushed.  The following is speculation. 
I think that the control module has a mirror image circuit (probably scaled) 
connected to a thermistor, such that when the mirror lock temperature exceeds 
32F (0C), the current drops or ceases.  I'll try to cold sink the system soon to
check it out further.  If this speculation is true, using another resistor value
might interfere with the circuit's proper function.

***                 ...Kirby    (Kirby A. Smith)                 ***
***              ksmith1@mailgw.sanders.lmco.com                 ***
***              [=]   kirby.a.smith@lmco.com                    ***
***  Opinions expressed herein are entirely those of the author. ***