Steve, and Listers,
There is nothing to the guts of an instrument voltage regulator. The schematic
diagram on
page N-30 of the Tiger shop manual depicts what goes on in there, and that
diagram is a
fair representation of the physical setup in there as well.
There is a bimetal strip with a contact point set in the end. This strip has a
length of
resistance wire wound around it, such that current flowing through the wire
will heat and
bend the strip, thus breaking the contact, which cools the strip, which then
straightens
out and makes contact again. This assembly is carefully tuned by Lucas gnomes
to produce
10 volts on average, pro-rated to 1967. In order for this to work, the
regulator has to
be grounded; in the case of my regulator, there was a tab with a hole for about
a #8
screw spot welded onto the case.
Last summer I found my gauges to be reading incorrectly, and traced the problem
to the
regulator being screwed to the back side of the (wood) dash. Screwed it to the
dash
support instead, and then found that the regulator would sometimes stick 'on'
(get a high
reading on the gauges), sometimes 'off' (get zero on the gauges), and very
occasionally
it would produce an approximately correct reading. Score one for the Prince of
Darkness.
I fixed the problem by removing the internals of the regulator and replacing
them with an
integrated-circuit design. So far, no problems. I will be publishing this
schematic
(maybe with layout and assembly instructions etc.) shortly after SUNI. If you
want a
prototype, bring out your dead (and maybe a small donation :), and I'll put one
together.
I think the problem with yours is that some of the wiring under the dash is
mixed up, or
else is shorted. There is no way that the blower operation should be tied into
the
regulator function at all; the regulator should only operate the two gauges.
Theo Smit
tsmit@home.com
tsmit@novatel.ca
B382002705
> Date: Sat, 26 Jun 1999 23:01:58 -0700
> From: steve sage <rootes@ix.netcom.com>
> Subject: Lord Lucas Helps!
>
> Here's another question for both lists. And Lord Lucas IS helping
> me....Helping me need a reservation at the funny farm!
>
> <snip>The speedo installed, out I went for a test drive and I noticed, trying
> out all the gadgets, my heater blower wasn't working, plus the water and
> fuel guages both pegged out to the right. Sure enough, on checking, I
> had pulled out one of the wires to the voltage regulator in doing the
> speedo install. Plugged that back in. The fan motor worked for 3-4
> seconds, then stopped. Guages read OK for a minute or so, then pegged
> out again. As per the shop manual, I checked voltage from the regulator
> to ground. When I first checked it, it read about 13 volts (the book
> calls for 10), so I figured I had somehow messed the regulator up in
> installing the speedo. I bought a new regulator from a parts store. When
> I went to install the new one, I unscrewed the attatching screw to the
> old one. Just for the heck of it, I tried the heater blower again, and
> it worked + the guages read correctly. This was with the old regulator
> un-grounded! I checked voltage and now it read the correct 10 volts. I
> screwed the old regulator back in and then the same problems came up
> again. I unscewed it, things worked!
>
> Then, the mechanical genius that I am, I just used electrical tape the
> hold the regulator in place. In re-installing my speedo, I bumped
> something under the dash a couple of times which was accompanied by very
> pretty sparks flying everywhere! A couple of bouts of this blew one of
> the 35 amp fuses. I replaced the fuse, check that all was working OK (it
> was), and re-installed the speedo. Guess what? Now the fan and the two
> guages again are inoperable.
>
> Do those regulators work intermittently when going into a failure mode?
> Seems like if I shook the wires going into it, on occasion the thing
> functioned.
>
> Anyway, tommorow I'll try installing the new voltage regulator which I'm
> a little concerned about as it does not have the attatching post on it
> to screw under the dash. Mechanic's wire? Or maybe just run a ground
> wire from it?
>
> Has anyone else had any of these fun Lucas experiences with this?
>
> Uh, oh. the SUNI trip is only 4 days away!
>
> Steve Sage
>
> ------------------------------
>
> End of tigers@autox.team.net digest
> ************************
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